Whole house ELECTRIC backup - PowerWall? Alternatives?

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need403bhelp
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Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

We have a 2200 sq ft townhouse on the Gulf Coast.

We have a small L shaped backyard. I basically dragged a permanent generator installation company out here against their will few years ago and they said no room for permanent generator.

We also have an HOA.

Looking for whole house power backup (2 ACs etc) solution that could work, seems Tesla PowerWall might be good option at least for <14-15 hour outages that could be installed completely indoors.

One quirk is that our circuit breaker is in the backyard not in the garage. So not sure if they would want to install outdoors anyway requiring HOA approval etc.

Any thoughts re Tesla Powerwall for this situation? Any good alternatives? Yes I am aware could buy gas generator but I think in the storm situation it would be prone to theft if left unattended outdoors.

Thank you!
CuriousGeorgeTx
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by CuriousGeorgeTx »

What size are your two A/C units? 14-15 hours seems like a long time to power one unit, let alone two. I suppose you can install multiple Powerwalls, but it will get pricey. I totally get what you are trying to do. We live near enough to the Gulf Coast that we have a whole home back up, but had plenty of room for a 32 kW Generac.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by snackdog »

A 20kw generator from Costco would run you $4k plus install. Needs about maybe seven feet square space. Is your yard smaller than that? How often does your power go out and for how long? Would a motel be cheaper?
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Sandtrap »

need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

We have a small L shaped backyard. I basically dragged a permanent generator installation company out here against their will few years ago and they said no room for permanent generator.

We also have an HOA.

Looking for whole house power backup (2 ACs etc) solution that could work, seems Tesla PowerWall might be good option at least for <14-15 hour outages that could be installed completely indoors.

One quirk is that our circuit breaker is in the backyard not in the garage. So not sure if they would want to install outdoors anyway requiring HOA approval etc.

Any thoughts re Tesla Powerwall for this situation? Any good alternatives? Yes I am aware could buy gas generator but I think in the storm situation it would be prone to theft if left unattended outdoors.

Thank you!
How many hours would a Tesla power wall system provide whole house power?
how large would that system be for you and how much would it cost?
3 powerwall units for 24 hours for "whole house" vs only essential circuits?

j :D
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need403bhelp
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

snackdog wrote: Sat Jul 06, 2024 1:20 pm A 20kw generator from Costco would run you $4k plus install. Needs about maybe seven feet square space. Is your yard smaller than that? How often does your power go out and for how long? Would a motel be cheaper?
We don't have seven yards square space. We might in one direction, the width is maybe 4-5 feet tops.
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need403bhelp
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

Sandtrap wrote: Sat Jul 06, 2024 1:42 pm
need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

We have a small L shaped backyard. I basically dragged a permanent generator installation company out here against their will few years ago and they said no room for permanent generator.

We also have an HOA.

Looking for whole house power backup (2 ACs etc) solution that could work, seems Tesla PowerWall might be good option at least for <14-15 hour outages that could be installed completely indoors.

One quirk is that our circuit breaker is in the backyard not in the garage. So not sure if they would want to install outdoors anyway requiring HOA approval etc.

Any thoughts re Tesla Powerwall for this situation? Any good alternatives? Yes I am aware could buy gas generator but I think in the storm situation it would be prone to theft if left unattended outdoors.

Thank you!
How many hours would a Tesla power wall system provide whole house power?
how large would that system be for you and how much would it cost?
3 powerwall units for 24 hours for "whole house" vs only essential circuits?

j :D
So Tesla website claimed up to 13 hours with 2 powerwalls for around $23k including install.

This is before anyone comes to look so who knows what ends up happening at that point.

I agree not very cost-effective for sure but DW doesn't like idea of power going out and DS is 3 years old.

We had one really bad outage 3.5 years ago when DW was pregnant, and scattered recent ones lasting a few hours which were significantly disruptive to DW.

I was hoping for some kind of solution. We can certainly afford $23k for peace of mind.

If we evacuate, DW also wants fridge running, not sure if 2 powerwalls might be able to do that if everything else is off for a few days.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by TomatoTomahto »

need403bhelp wrote: Sat Jul 06, 2024 1:48 pm If we evacuate, DW also wants fridge running, not sure if 2 powerwalls might be able to do that if everything else is off for a few days.
Assuming it’s a modern fridge, if you don’t open the doors, 2 Powerwalls should have an easy time keeping the contents cold.

Have you figured out how much electrical load you typically run?

Have you figured out how much load your “essential appliances” are? For example, we don’t run our sauna, clothes dryer, EV charger during an outage (although we could if we had to).
I get the FI part but not the RE part of FIRE.
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id0ntkn0wjack
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by id0ntkn0wjack »

need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

If that's the Gulf Coast of Texas, you might want to check out Base Power:

https://www.basepowercompany.com/
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need403bhelp
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

id0ntkn0wjack wrote: Sat Jul 06, 2024 2:00 pm
need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

If that's the Gulf Coast of Texas, you might want to check out Base Power:

https://www.basepowercompany.com/
Thanks, I'll check this out. Any personal experience?
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need403bhelp
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

TomatoTomahto wrote: Sat Jul 06, 2024 1:56 pm
need403bhelp wrote: Sat Jul 06, 2024 1:48 pm If we evacuate, DW also wants fridge running, not sure if 2 powerwalls might be able to do that if everything else is off for a few days.
Assuming it’s a modern fridge, if you don’t open the doors, 2 Powerwalls should have an easy time keeping the contents cold.

Have you figured out how much electrical load you typically run?

Have you figured out how much load your “essential appliances” are? For example, we don’t run our sauna, clothes dryer, EV charger during an outage (although we could if we had to).
We have not. I honestly don't know how to do that?

The only thing we run pretty frequently now that we might not in an outage I think is the clothes washer, clothes dryer, and dishwasher. Sauna basically never runs.
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need403bhelp
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

snackdog wrote: Sat Jul 06, 2024 1:20 pm A 20kw generator from Costco would run you $4k plus install. Needs about maybe seven feet square space. Is your yard smaller than that? How often does your power go out and for how long? Would a motel be cheaper?
Btw I think the correct cost comparison is to moving to a different house rather than staying at a motel.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by BarbK »

My friend is going with EcoFlow Delta Pro Ultra. Is is small and stackable. It looks like it is mainly used for backup, but she plans on adding solar panels (not on roof to it).
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by TomatoTomahto »

need403bhelp wrote: Sat Jul 06, 2024 2:16 pm
id0ntkn0wjack wrote: Sat Jul 06, 2024 2:00 pm
need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

If that's the Gulf Coast of Texas, you might want to check out Base Power:

https://www.basepowercompany.com/
Thanks, I'll check this out. Any personal experience?
I have no background with Base Power (had never heard of them), but a look at their web site indicates that they install a 20 kWh battery, which roughly the capacity of 1.5 Powerwall 2s. If your outages are short duration, and you have access to this, it’s not shabby.
I get the FI part but not the RE part of FIRE.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Pdxnative »

I wouldn’t limit myself to Tesla PW. Enphase and Franklin make great LFP batteries for home backup.

Base is a good idea if they’re available in your area. The founders were on the Volts podcast recently.

Finally, given what you seem to be willing to spend, you might consider if the various vehicle to home options would work for you. Ford and GM offer this in some of their EVs. So if you’re in the market for a vehicle in the near term you could consider this. It’s not a cheap option but the battery capacity would be enormous. If you have a different car for evacuation this might work.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by TomatoTomahto »

Pdxnative wrote: Sat Jul 06, 2024 4:00 pm

Finally, given what you seem to be willing to spend, you might consider if the various vehicle to home options would work for you. Ford and GM offer this in some of their EVs. So if you’re in the market for a vehicle in the near term you could consider this. It’s not a cheap option but the battery capacity would be enormous.
We have what is considered a large amount of battery capacity (52 kWh) for a residence, but EVs regularly top 90 or 100 kWh.
I get the FI part but not the RE part of FIRE.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by HawkeyePierce »

I live in an area where the utility has started shutting off power to large areas on high fire risk days so I've been looking into this too. My current plan is to install a manual transfer switch on my panel, then get a Goal Zero home battery to power only essential circuits. I might add some solar panels.

https://goalzero.com/products/8kwh-have ... ery-backup
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by CascadiaSoonish »

BarbK wrote: Sat Jul 06, 2024 2:25 pm My friend is going with EcoFlow Delta Pro Ultra. Is is small and stackable. It looks like it is mainly used for backup, but she plans on adding solar panels (not on roof to it).
I'm using an Ecoflow Delta Pro with the transfer switch and an array of solar panels for a freestanding small outbuilding. Plenty of power to continuously run the A/C and provide power over the summer. We'll see how it does in the winter -- might need to switch the mini split to grid supplied power using the transfer switch if the solar can't keep up. But in a pinch the Ecoflow could definitely run the heat for a while in winter.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by LotsaGray »

need403bhelp wrote: Sat Jul 06, 2024 2:23 pm
snackdog wrote: Sat Jul 06, 2024 1:20 pm A 20kw generator from Costco would run you $4k plus install. Needs about maybe seven feet square space. Is your yard smaller than that? How often does your power go out and for how long? Would a motel be cheaper?
Btw I think the correct cost comparison is to moving to a different house rather than staying at a motel.
Lived on GC for 35 yrs. Been through multiple hurricanes including multi week power outages. I have never chosen to install whole house generator or back up. We went through a multi day outage from an ice storm with a 1.5 yo. So I understand the inconvenience but my DW chose (actually demanded) I take her back to a house wo power knowing it would be days and I would not be there. So I definitely did not have a spouse pushing for a generator (I am not saying either position is right or wrong).

With that background, I would never even consider putting in $10/sq ft power back up. We have about 3000 sq ft and for less than $1100 I have a system that allows me to create a comfortable living space. We have portable 6500 W generator, two window AC units, manual electrical disconnect/transfer switch. This system easily powered our 2 refrigerators, 1deep freeze, both AC units, the whole house except for 220v circuits (though obviously not all at same time). We lived like this for couple of weeks after the last hurricane and all we really lacked was hot running water (we boiled water on propane grill and also had a solar camping shower. We even had swimming pool up and running.

That is why I would never dream of the costs you are considering. We have considered whole house g3nerator and if we had natgas might do it. I think you can achieve a much cheaper and better solution. Batteries might be great for power outage from a thunderstorm but they won’t really help for a major one. I am not sure you need a whole house solution but if you do there are better ones that will cost less.
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Watty
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Watty »

You are in a townhouse with a three year old. Especially if you have more kids this might not be a long term home for you so it would be good to consider that in your planning.

I don't have a clue if having an you would get much of your money back when you sell the townhouse or if it might even be a negative for some buyers if there are ongoing maintenance costs.

If you are not likely to be in the townhouse for a very long time then it might be best to wait until you move to get a house with an elaborate backup system. I don't know if it would be practical to move something like a powerwall to your next house.

Your HOA might also object to the noise of a generator when it tested each month or during a power outage. You would also need to research how to store gasoline in a townhouse with safety and HOA rules.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Sandtrap »

need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

We have a small L shaped backyard. I basically dragged a permanent generator installation company out here against their will few years ago and they said no room for permanent generator.

We also have an HOA.

Looking for whole house power backup (2 ACs etc) solution that could work, seems Tesla PowerWall might be good option at least for <14-15 hour outages that could be installed completely indoors.

One quirk is that our circuit breaker is in the backyard not in the garage. So not sure if they would want to install outdoors anyway requiring HOA approval etc.

Any thoughts re Tesla Powerwall for this situation? Any good alternatives? Yes I am aware could buy gas generator but I think in the storm situation it would be prone to theft if left unattended outdoors.

Thank you!
Here's a recent long post/thread on Home generator backup systems that might be helpful for you.
Boglehead forum link to:
"What kind of generator for home backup?"
viewtopic.php?t=336294&hilit=generator
j
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need403bhelp
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

Sandtrap wrote: Sun Jul 07, 2024 7:51 am
need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

We have a small L shaped backyard. I basically dragged a permanent generator installation company out here against their will few years ago and they said no room for permanent generator.

We also have an HOA.

Looking for whole house power backup (2 ACs etc) solution that could work, seems Tesla PowerWall might be good option at least for <14-15 hour outages that could be installed completely indoors.

One quirk is that our circuit breaker is in the backyard not in the garage. So not sure if they would want to install outdoors anyway requiring HOA approval etc.

Any thoughts re Tesla Powerwall for this situation? Any good alternatives? Yes I am aware could buy gas generator but I think in the storm situation it would be prone to theft if left unattended outdoors.

Thank you!
Here's a recent long post/thread on Home generator backup systems that might be helpful for you.
Boglehead forum link to:
"What kind of generator for home backup?"
viewtopic.php?t=336294&hilit=generator
j
Thanks will check it out!

We are planning on keeping this place long term not moving anytime soon (lived 5 years out of planned 30).

Looks like we used 47 kWh per day per last electric bill. Not sure if this is how one estimates load?
beardsicles
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by beardsicles »

If your concern is keeping the fridge and AC on once a year in the event of an emergency, buy an EV with bidirectional charging. An EV is just a huge battery wall that also happens to be a car.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by TomatoTomahto »

need403bhelp wrote: Sun Jul 07, 2024 9:05 am Looks like we used 47 kWh per day per last electric bill. Not sure if this is how one estimates load?
That’s a start. That’s quite a lot for batteries to provide in a long term outage. Even an EV will, at most, give you two days of backup if you don’t pay attention to what gets used during an outage.

Do you have an electrician/energy savvy friend who could do an evaluation of your electrical usage while having a friendly beer? :beer
I get the FI part but not the RE part of FIRE.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Colorado Guy »

need403bhelp wrote: Sun Jul 07, 2024 9:05 am Looks like we used 47 kWh per day per last electric bill. Not sure if this is how one estimates load?
Starting with kwh, look at KW usage (peak power usage) to size your generator. So, if you used all that 47 kwh in one hour, that is a peak kW of 47 KW. If it took 10 hours, that is a (rough estimate) of 4.7 kW. If you are able to not run clothes dryers/saunas / etc., you can probably cut that estimate by 1/3 to 1/2, so your peak KW usage is somewhere between 2.4 kW and 3 KW. That is the minimum size generator you should be looking for. You can check all your equipment KW ratings to get a more firm estimate (particularly for your AC units), or get more beer to your energy savvy friend. :happy

FYI, I have a 7 KW gasoline portable generator (on wheels) stored in my garage. When I need it, I move it to the backyard near my breaker box. For me, that is an oversized generator, but still is only 3x3 feet in size. For house wiring, an electrician installed a transfer panel and moved critical circuits to the transfer panel. Usage is infrequent (only once this year so far).

For piece of mind, I understand that motivation. Still, I believe you can achieve piece of mind for a lot less than a Tesla PowerWall. Friend of mine had a full Tesla PowerWall setup installed at his home 2 years ago, and has not used it other than just testing it out. Plus, I seriously doubt when you sell your home you would get back the money on a $23k or more system.

Good luck.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

Pdxnative wrote: Sat Jul 06, 2024 4:00 pm I wouldn’t limit myself to Tesla PW. Enphase and Franklin make great LFP batteries for home backup.

Base is a good idea if they’re available in your area. The founders were on the Volts podcast recently.

Finally, given what you seem to be willing to spend, you might consider if the various vehicle to home options would work for you. Ford and GM offer this in some of their EVs. So if you’re in the market for a vehicle in the near term you could consider this. It’s not a cheap option but the battery capacity would be enormous. If you have a different car for evacuation this might work.
Any good ways to price Enphase and Franklin installs?

Tesla lets you price PW directly via https://www.tesla.com/powerwall/design and order an install.

Enphase seems to just send you a "cost savings" for solar power (which we don't need as that definitely won't go with HOA) https://enphase.com/

Franklin does seem to have a contact form https://www.franklinwh.com/homeowner/

Thanks!!!

EDITED TO ADD: Also, how long do these kind of systems generally last if only used for backup power?

EDITED TO ALSO ADD: Looks like I can get per 15 minute consumption from my utility:

Image
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TomatoTomahto
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by TomatoTomahto »

need403bhelp wrote: Sun Jul 07, 2024 2:14 pm Also, how long do these kind of systems generally last if only used for backup power?
I figure probably twice as long as the warranty. You’ll have some degradation over the years, but iirc the warranty states that the capacity will still be better than 70% of spec. My Sonnen batteries and Enphase batteries are warrantied for 10 years. Some Sonnen batteries (possibly something you might want to look into) are warranted for 15 years.

Fwiw, my batteries are various ages (between 5 and 6 years) and I haven’t noticed any degradation. I also use them to time shift, so they’re not purely backup only.
I get the FI part but not the RE part of FIRE.
mark_in_denver
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by mark_in_denver »

LotsaGray wrote: Sat Jul 06, 2024 7:25 pm
need403bhelp wrote: Sat Jul 06, 2024 2:23 pm
snackdog wrote: Sat Jul 06, 2024 1:20 pm A 20kw generator from Costco would run you $4k plus install. Needs about maybe seven feet square space. Is your yard smaller than that? How often does your power go out and for how long? Would a motel be cheaper?
Btw I think the correct cost comparison is to moving to a different house rather than staying at a motel.
Lived on GC for 35 yrs. Been through multiple hurricanes including multi week power outages. I have never chosen to install whole house generator or back up. We went through a multi day outage from an ice storm with a 1.5 yo. So I understand the inconvenience but my DW chose (actually demanded) I take her back to a house wo power knowing it would be days and I would not be there. So I definitely did not have a spouse pushing for a generator (I am not saying either position is right or wrong).

With that background, I would never even consider putting in $10/sq ft power back up. We have about 3000 sq ft and for less than $1100 I have a system that allows me to create a comfortable living space. We have portable 6500 W generator, two window AC units, manual electrical disconnect/transfer switch. This system easily powered our 2 refrigerators, 1deep freeze, both AC units, the whole house except for 220v circuits (though obviously not all at same time). We lived like this for couple of weeks after the last hurricane and all we really lacked was hot running water (we boiled water on propane grill and also had a solar camping shower. We even had swimming pool up and running.

That is why I would never dream of the costs you are considering. We have considered whole house g3nerator and if we had natgas might do it. I think you can achieve a much cheaper and better solution. Batteries might be great for power outage from a thunderstorm but they won’t really help for a major one. I am not sure you need a whole house solution but if you do there are better ones that will cost less.
Same here. I spent about a grand for a 6500W gen. It will power the AC, fridge and a couple other things....good enough for us.
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TomatoTomahto
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by TomatoTomahto »

Am I missing something, or are generators out of the question for OP? It sounds like a very small lot and a powerful HOA.
I get the FI part but not the RE part of FIRE.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by slippinsurlies »

How about a small portable generator? Think about one on wheels that is stored in your garage. If the power goes out, roll that bad Jonny into the backyard and gas 'er up. Get one that has enough power for your essentials, like maybe the fridge and a single-room AC unit. If you're only doing it for a day or two, does it really matter if you are just running an extension cord from your generator, through a window, and into the kitchen?

Sure, the HOA says "no generator,"... but the power is out, and all your neighbors either a) left to a hotel or b) are asking you to store stuff in your working refrigerator. That seems like a reasonable extenuating circumstance. As soon as the power goes back on, you turn it off and roll it back into the garage.

I'm a perpetual renter, move a lot, and frequently don't have a garage or backyard, so I can't speak from personal experience... but this setup is basically what my sister has. Works out for her when the power goes out once every 5 or 6 years.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Pdxnative »

need403bhelp wrote: Sun Jul 07, 2024 2:14 pm
Pdxnative wrote: Sat Jul 06, 2024 4:00 pm I wouldn’t limit myself to Tesla PW. Enphase and Franklin make great LFP batteries for home backup.

Base is a good idea if they’re available in your area. The founders were on the Volts podcast recently.

Finally, given what you seem to be willing to spend, you might consider if the various vehicle to home options would work for you. Ford and GM offer this in some of their EVs. So if you’re in the market for a vehicle in the near term you could consider this. It’s not a cheap option but the battery capacity would be enormous. If you have a different car for evacuation this might work.
Any good ways to price Enphase and Franklin installs?

Tesla lets you price PW directly via https://www.tesla.com/powerwall/design and order an install.

Enphase seems to just send you a "cost savings" for solar power (which we don't need as that definitely won't go with HOA) https://enphase.com/

Franklin does seem to have a contact form https://www.franklinwh.com/homeowner/

Thanks!!!

EDITED TO ADD: Also, how long do these kind of systems generally last if only used for backup power?

EDITED TO ALSO ADD: Looks like I can get per 15 minute consumption from my utility:

Image
I think for those brands you’ll want to get in touch with solar installers (or electricians) in your area and just ask for a quote without solar. Most can probably do that without coming out. Might just need a photo of your current panel.

Another thing to consider, since folks are bringing up costs, is whether your utility has plans that you could take advantage of with a battery. For example, time of use rates you could arbitrage, virtual power plant programs, etc.

As far as amount of time the batteries will give you, it really depends what you consider critical loads/use. If you’re not running AC or appliances aside from the refrigerator you’ll have a lot more time than if you continue your 40 kWh/day consumption (one PW is around 13kwh I believe, so 2 might provide half a day at normal consumption).

ETA: if by “last” you meant how many years, I think Tesla warranty is 10 years and others are moving to 15. There’ll be some degradation but I’d expect at least 80-90% capacity at 10-15 years and a well functioning battery for at least 20. The new LFP chemistry should have less degradation and could be great for decades with minimal degradation.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Sandtrap »

need403bhelp wrote: Sun Jul 07, 2024 9:05 am
Sandtrap wrote: Sun Jul 07, 2024 7:51 am
need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

We have a small L shaped backyard. I basically dragged a permanent generator installation company out here against their will few years ago and they said no room for permanent generator.

We also have an HOA.

Looking for whole house power backup (2 ACs etc) solution that could work, seems Tesla PowerWall might be good option at least for <14-15 hour outages that could be installed completely indoors.

One quirk is that our circuit breaker is in the backyard not in the garage. So not sure if they would want to install outdoors anyway requiring HOA approval etc.

Any thoughts re Tesla Powerwall for this situation? Any good alternatives? Yes I am aware could buy gas generator but I think in the storm situation it would be prone to theft if left unattended outdoors.

Thank you!
Here's a recent long post/thread on Home generator backup systems that might be helpful for you.
Boglehead forum link to:
"What kind of generator for home backup?"
viewtopic.php?t=336294&hilit=generator
j
Thanks will check it out!

We are planning on keeping this place long term not moving anytime soon (lived 5 years out of planned 30).

Looks like we used 47 kWh per day per last electric bill. Not sure if this is how one estimates load?
To estimate "total load" or "maximum sustained load/power use" for the "entire house" (not select circuits).
1. Take a picture of your electrical panel. Note which breakers are for what circuits. Chart the breaker amp rating for each breaker.
2. Walk around the house and take pictures of each "power user", Chart that.
a) the kitchen: electric stove, what kind, oven, what kind, microwave, range fan, refrig what kind size amp load.
3. Garage: HVAC units, take pictures, chart what kind, model, amp rating. Refrigerator. Large freezer?
Like that.
In a bedroom, there's just outlets and lights, no demand like a refrigerator so just list that.
4. Well pump. What phase. Amp rating.
5. Elec heat or gas heat. etc.
Like that.
6. Add up the "wattage" of each thing to get your "total load" number.

So from all this, add up how much your energy demand would be if it were summer and you had the central air on, and you were in the kitchen using everything, and people were taking a shower so the elec water heater is on, like that.

Start ups take a lot more juice, so you increase your total energy demand figure by "x" percentage. That's your target for a "whole house" energy system. Some systems are only for short term use, a few hours, etc. Some can sustain the home for much longer. I depends on what you want.

For example: our home has a "whole house" automatic backup system that can sustain the entire home for weeks on end. We have a 48 KW Generac and a 1000 gallon underground propane tank next to it. Our home is over 5000 sf with a lot of utilities, plus outbuildings, well pump, etc. So the energy demand could potentially be very high in a sustained outage. See?

An electrical contractor will calc your total energy demand for a whole house system that can has no limit on how long it can sustain power. That's the starting point.
To reduce costs, there can be only select circuits that are energized which cuts down on your kw demand. It's up to you.

j
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LotsaGray
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by LotsaGray »

TomatoTomahto wrote: Sun Jul 07, 2024 2:42 pm Am I missing something, or are generators out of the question for OP? It sounds like a very small lot and a powerful HOA.
A permanently installed whole house generator is probably a no go. But I don’t actually see a need for that type of solution
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need403bhelp
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by need403bhelp »

LotsaGray wrote: Sun Jul 07, 2024 5:05 pm
TomatoTomahto wrote: Sun Jul 07, 2024 2:42 pm Am I missing something, or are generators out of the question for OP? It sounds like a very small lot and a powerful HOA.
A permanently installed whole house generator is probably a no go. But I don’t actually see a need for that type of solution
Yes a portable gas generator is not a horrible solution.

However, some caveats:
(i) During natural disasters, people stop being polite. We do live next to a not quite upscale apartment complex turned AirBNB rental. Our backyard faces right into their parking lot with a wood fence as separator. If I left a generator running there after a hurricane, I don't think it is out of the question it would get stolen.
(ii) Getting gas during a natural disaster would also likely be difficult to power such a generator. Storing gas in a garage seems somewhat risky.
(iii) Well those are main reasons why it may not be a great idea. Also for a brief (few hour) power outage, seems like it would be a rather large inconvenience to get the generator up and running. And for a longer time, I think (i) and (ii) would come up.

Thanks everyone for you helpful replies!
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by vfinx »

beardsicles wrote: Sun Jul 07, 2024 9:08 am If your concern is keeping the fridge and AC on once a year in the event of an emergency, buy an EV with bidirectional charging. An EV is just a huge battery wall that also happens to be a car.
I very much hope this becomes ubiquitous. The EV I purchased doesn’t have any vehicle-to-load capability. But it certainly won’t be our last EV purchase.

The capacity ratings of the home stations seem pathetic compared to an EV. Fast charging an electric F150 and bringing home 120 kWh to a house without power is the modern equivalent of a Marlboro Man.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by LotsaGray »

need403bhelp wrote: Sun Jul 07, 2024 9:49 pm
LotsaGray wrote: Sun Jul 07, 2024 5:05 pm
TomatoTomahto wrote: Sun Jul 07, 2024 2:42 pm Am I missing something, or are generators out of the question for OP? It sounds like a very small lot and a powerful HOA.
A permanently installed whole house generator is probably a no go. But I don’t actually see a need for that type of solution
Yes a portable gas generator is not a horrible solution.

However, some caveats:
(i) During natural disasters, people stop being polite. We do live next to a not quite upscale apartment complex turned AirBNB rental. Our backyard faces right into their parking lot with a wood fence as separator. If I left a generator running there after a hurricane, I don't think it is out of the question it would get stolen.
(ii) Getting gas during a natural disaster would also likely be difficult to power such a generator. Storing gas in a garage seems somewhat risky.
(iii) Well those are main reasons why it may not be a great idea. Also for a brief (few hour) power outage, seems like it would be a rather large inconvenience to get the generator up and running. And for a longer time, I think (i) and (ii) would come up.

Thanks everyone for you helpful replies!
1. People have been storing gas in garages for a century. Stored properly it is relatively safe. Remember you can literally put a match out in liquid gasoline. It is the vapor that will burn. If you keep it in a closed approved container, you literally have to get the ignition source into the container. But if that isn’t safe enough both diesel and propane are portable options.

Don’t forget that millions of homes have 40 gal of gasoline stored in garages every night.

2. Been through multiple hurricanes where the entire area was wo electricity. The times we evacuated but came right back, we brought gas with us but it was not necessary. The time we rode it out, local stations were open by the time we cut our way out the next day. Plus hurricanes are not surprise events. You have plenty of warning to stock up ahead of time. (This also applies to the safe storage issue. You can go get gas for a week 2days before the storm (you can always put in your ice car if you don’t need it) btw the prices were not bad either.

3. Stealing the generator is certainly possible but it isn’t easy or you can make difficult. After one hurricane, the first here in a long time, stealing generators was happening some but the big target was generators powering crossing gates and lights at railroads and stop lights. Our solution was to set up a large temp dog kennel but put the generator inside with our two outside dogs.

If your fence is still standing, it would be difficult. You can’t pick up a generator and toss it over a fence. If someone going to steal it, your have warning be cause they have to turn off your power. Also every time, here at least, neighborhood got very protective. People did not just wander into neighborhood.

TLDR. Of the three issues mentioned, only the theft really has merit. Even that feels overstated ime
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by gamboolman »

need403bhelp

We live in The Woodlands - so Gulf Coast with you. Retired 1-Feb-21.

Upon retiring, we installed a 26KW whole house Generac Stand By Genset that is fueled by Natural Gas. We had to replace our 20 year old Main Breaker Panel to our house - but this needed doing anyway. Our HOA had no objections.

Total installed cost for the Stand By Genset was about $15K ish....

The cost for Main Breaker replacement was an additional ~$4k to $5K.

We let our neighbors plug in a extension cord to run their Freezer and Refrigerator and a few fans.

Do recommend a whole house Standby Genset - if you can afford it

We are getting ready for Beryl to hit our house in afew hours....
Image
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by TomatoTomahto »

vfinx wrote: Sun Jul 07, 2024 10:03 pm
beardsicles wrote: Sun Jul 07, 2024 9:08 am If your concern is keeping the fridge and AC on once a year in the event of an emergency, buy an EV with bidirectional charging. An EV is just a huge battery wall that also happens to be a car.
I very much hope this becomes ubiquitous. The EV I purchased doesn’t have any vehicle-to-load capability. But it certainly won’t be our last EV purchase.

The capacity ratings of the home stations seem pathetic compared to an EV. Fast charging an electric F150 and bringing home 120 kWh to a house without power is the modern equivalent of a Marlboro Man.
I hope for this also, but have to mention that the charge in your EV might not be able to be fast charged outside the home if there’s a significant grid outage. So, keep your EV charged.
I get the FI part but not the RE part of FIRE.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Sandtrap »

gamboolman wrote: Mon Jul 08, 2024 12:30 am need403bhelp

We live in The Woodlands - so Gulf Coast with you. Retired 1-Feb-21.

Upon retiring, we installed a 26KW whole house Generac Stand By Genset that is fueled by Natural Gas. We had to replace our 20 year old Main Breaker Panel to our house - but this needed doing anyway. Our HOA had no objections.

Total installed cost for the Stand By Genset was about $15K ish....

The cost for Main Breaker replacement was an additional ~$4k to $5K.

We let our neighbors plug in a extension cord to run their Freezer and Refrigerator and a few fans.

Do recommend a whole house Standby Genset - if you can afford it

We are getting ready for Beryl to hit our house in afew hours....
Image
A reasonable price for a well thought out system and "peace of mind".

We just got our permits to go ahead with a 48kw Liquid Cooled Generac auto Whole House/Property power system. Also a 1000 gallon underground propane tank nearby. Total costs including trenching, etc: just under 50k dollars usd.

Hope you do okay through your storm.
Stay safe and stress free.


Good thing you had that power system done.
j
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Carl53
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Carl53 »

Sandtrap wrote: Mon Jul 08, 2024 6:11 am
A reasonable price for a well thought out system and "peace of mind".

We just got our permits to go ahead with a 48kw Liquid Cooled Generac auto Whole House/Property power system. Also a 1000 gallon underground propane tank nearby. Total costs including trenching, etc: just under 50k dollars usd.

Hope you do okay through your storm.
Stay safe and stress free.


Good thing you had that power system done.
j
How many hours is your propane system projected to work? I was concerned about my inlaws 7k system with a 300 gallon tank, but it was never challenged for more than a couple hours.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by Sandtrap »

Carl53 wrote: Mon Jul 08, 2024 7:11 am
Sandtrap wrote: Mon Jul 08, 2024 6:11 am
A reasonable price for a well thought out system and "peace of mind".

We just got our permits to go ahead with a 48kw Liquid Cooled Generac auto Whole House/Property power system. Also a 1000 gallon underground propane tank nearby. Total costs including trenching, etc: just under 50k dollars usd.

Hope you do okay through your storm.
Stay safe and stress free.


Good thing you had that power system done.
j
How many hours is your propane system projected to work? I was concerned about my inlaws 7k system with a 300 gallon tank, but it was never challenged for more than a couple hours.
On The Generac website, you can look up various air or water cooled units of the same KW size as yours, and engine size. On the specs, it will have the average "gallons per hour" use under sustained average loads.
For example, our 48 kw liquid cooled with a 4.5 litre engine at a mile high altitude can consume from 7 to 10 gallons per hour. That's a lot. And, because of that, the gas feed line is upsized to 1-1/4 inch. So, with a 1000 gallon underground propane tank it can run awhile.

The air cooled generators all have overheat protection and shut down. So, if you live in a hot climate, that is a factor.

A 300 gallon tank is marginal, very marginal for a 7k system, but that depends on use and how long they need it to run. There are a lot of variables. What circuits are energized, demand loads, etc. It can use up to 2-4 gallons per hour. Or, maybe they only have very very essential circuits energized on the transfer box, then the generator might just sip along for a long time. It is safer to calc the highest that night be needed.

I think propane tanks are only filled up to 70-80 percent. So, a 300 gallon tank on "full" does not have 300 gallons,

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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by neilpilot »

TomatoTomahto wrote: Mon Jul 08, 2024 5:33 am
vfinx wrote: Sun Jul 07, 2024 10:03 pm
beardsicles wrote: Sun Jul 07, 2024 9:08 am If your concern is keeping the fridge and AC on once a year in the event of an emergency, buy an EV with bidirectional charging. An EV is just a huge battery wall that also happens to be a car.
I very much hope this becomes ubiquitous. The EV I purchased doesn’t have any vehicle-to-load capability. But it certainly won’t be our last EV purchase.

The capacity ratings of the home stations seem pathetic compared to an EV. Fast charging an electric F150 and bringing home 120 kWh to a house without power is the modern equivalent of a Marlboro Man.
I hope for this also, but have to mention that the charge in your EV might not be able to be fast charged outside the home if there’s a significant grid outage. So, keep your EV charged.
While we typically charge to 80%, have gone to 90-100% evening before a major storm was forecast.

Also even though our EV isn't designed to provide backup power, a $250 inverter can be connected to extension cords to power fridge, furnace and other essential items. Estimate I can run a furnace on my EV for 5-8 days in a pinch.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by just frank »

neilpilot wrote: Mon Jul 08, 2024 7:46 am
TomatoTomahto wrote: Mon Jul 08, 2024 5:33 am
vfinx wrote: Sun Jul 07, 2024 10:03 pm
beardsicles wrote: Sun Jul 07, 2024 9:08 am If your concern is keeping the fridge and AC on once a year in the event of an emergency, buy an EV with bidirectional charging. An EV is just a huge battery wall that also happens to be a car.
I very much hope this becomes ubiquitous. The EV I purchased doesn’t have any vehicle-to-load capability. But it certainly won’t be our last EV purchase.

The capacity ratings of the home stations seem pathetic compared to an EV. Fast charging an electric F150 and bringing home 120 kWh to a house without power is the modern equivalent of a Marlboro Man.
I hope for this also, but have to mention that the charge in your EV might not be able to be fast charged outside the home if there’s a significant grid outage. So, keep your EV charged.
While we typically charge to 80%, have gone to 90-100% evening before a major storm was forecast.

Also even though our EV isn't designed to provide backup power, a $250 inverter can be connected to extension cords to power fridge, furnace and other essential items. Estimate I can run a furnace on my EV for 5-8 days in a pinch.
Same here, I backfeed my sine wave inverter to selected 120V circuits in my house. Maybe total of 100 hours runtime like that since 2016. I've used 4 different EVs.

However, usually the 12V route is limited to about 1100W output continuous. 2 AC's for OP would be a no go. One AC would be doable, and everyone could camp out in one room to sleep if needed. Ofc, a powerwall is not going to run 2 ACs for very long, so they might still camp out in that scenario.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by neilpilot »

just frank wrote: Mon Jul 08, 2024 7:57 am
neilpilot wrote: Mon Jul 08, 2024 7:46 am
TomatoTomahto wrote: Mon Jul 08, 2024 5:33 am
vfinx wrote: Sun Jul 07, 2024 10:03 pm
beardsicles wrote: Sun Jul 07, 2024 9:08 am If your concern is keeping the fridge and AC on once a year in the event of an emergency, buy an EV with bidirectional charging. An EV is just a huge battery wall that also happens to be a car.
I very much hope this becomes ubiquitous. The EV I purchased doesn’t have any vehicle-to-load capability. But it certainly won’t be our last EV purchase.

The capacity ratings of the home stations seem pathetic compared to an EV. Fast charging an electric F150 and bringing home 120 kWh to a house without power is the modern equivalent of a Marlboro Man.
I hope for this also, but have to mention that the charge in your EV might not be able to be fast charged outside the home if there’s a significant grid outage. So, keep your EV charged.
While we typically charge to 80%, have gone to 90-100% evening before a major storm was forecast.

Also even though our EV isn't designed to provide backup power, a $250 inverter can be connected to extension cords to power fridge, furnace and other essential items. Estimate I can run a furnace on my EV for 5-8 days in a pinch.
Same here, I backfeed my sine wave inverter to selected 120V circuits in my house. Maybe total of 100 hours runtime like that since 2016. I've used 4 different EVs.

However, usually the 12V route is limited to about 1100W output continuous. 2 AC's for OP would be a no go. One AC would be doable, and everyone could camp out in one room to sleep if needed. Ofc, a powerwall is not going to run 2 ACs for very long, so they might still camp out in that scenario.
I don't plan to run AC off my EV. Refrigerators (2), fans, lights, TV and modem/computer total a small relative load that my EV can run for up to a week. In winter, downstairs furnace is a minor load relative to AC, and will heat upstairs as well.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by firebirdparts »

need403bhelp wrote: Sat Jul 06, 2024 2:16 pm We have not. I honestly don't know how to do that?

The only thing we run pretty frequently now that we might not in an outage I think is the clothes washer, clothes dryer, and dishwasher. Sauna basically never runs.
You can just look at the amperage sizes on the breakers, but I'll save you the trouble. The big breakers will be:
Air conditioning (usually indoor/outdoor parts on separate breakers FWIW).
Water Heater
Oven/Range/Cooktop
Dryer
Hot tub if you had one

The one that gets you is the water heater, as it turns on without you knowing. The rest you simply choose not to use. The biggest wire in the house goes to the dryer, so don't use it. It doesn't really do anything that you need. You can find something to wear. So "power management" mostly just means you need to kill power to the water heater.

A range will have a pretty big breaker, but that supports all 4 eyes and the broiler on at the same time. If you just use one eye, or just the oven, it's not that big.

The big game then for hurricanes is to get air conditioning, as you know. They are really not that big users anymore due to the mandated efficiency, but they do take a big inrush of current to start up. In your house you might be able to run just one, which I guess doubles the run time on a battery. You can easily find out how many continuous amps it uses, but you may not know how many minutes a day it wants to run. You may have to guess at that.
This time is the same
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by neilpilot »

firebirdparts wrote: Mon Jul 08, 2024 10:59 am
The big game then for hurricanes is to get air conditioning, as you know. They are really not that big users anymore due to the mandated efficiency, but they do take a big inrush of current to start up. In your house you might be able to run just one, which I guess doubles the run time on a battery. You can easily find out how many continuous amps it uses, but you may not know how many minutes a day it wants to run. You may have to guess at that.
Assuming there are 2 AC units in a 2 story home, most users would chose to run the upstairs AC. However, this the choice that will result in the larger power draw. With only the upstairs AC running, this unit will work even harder than normal since it will also try to cool the downstairs. If you do run only the upstairs unit, it can typically run 25% to 70% harder than normal.

A smarter choice, assuming your power source is limited, would be to run the downstairs unit only, and consider elevating the thermostat setting. Of course the upstairs will be hot as H*, consider opening the windows upstairs.

In our case all 3 AC's remain down during a power outage, windows are opened at night and box fans take over. Thankfully, our 2 hot water tanks are gas and use no electricity.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by ExtraCool »

need403bhelp wrote: Sat Jul 06, 2024 12:59 pm We have a 2200 sq ft townhouse on the Gulf Coast.

We have a small L shaped backyard. I basically dragged a permanent generator installation company out here against their will few years ago and they said no room for permanent generator.

We also have an HOA.

Looking for whole house power backup (2 ACs etc) solution that could work, seems Tesla PowerWall might be good option at least for <14-15 hour outages that could be installed completely indoors.

One quirk is that our circuit breaker is in the backyard not in the garage. So not sure if they would want to install outdoors anyway requiring HOA approval etc.

Any thoughts re Tesla Powerwall for this situation? Any good alternatives? Yes I am aware could buy gas generator but I think in the storm situation it would be prone to theft if left unattended outdoors.

Thank you!
I didn’t understand your mention if a “circuit breaker is in the backyard”. Maybe you mean utility disconnect and meter?

Some general thoughts below:
1) understand your power (kW) usage per 15-min
Take each 15min (kWh) energy data from smart meter Texas and divide by (15/60) to get the power (kW) usage in each 15-min interval, ie., kWh/h = kW. This gives you the power load in each 15-min interval. The Smart Meter Texas data can be downloaded as excel file for some time period like a month or a year. Determine the kW power load for hot summer days, eg., in July or August, as well as winter/fall/spring days when no AC usage.

2) determine whole vs partial backup need
My recommendation is to focus on basic usage need, ie., partial backup with no ACs. This would include most of your critical loads like router/wifi, lights, fan blower motor for gas furnace (if winter day or in circulate** mode when no AC), electric ignition for a gas tankless water heater, microwave, refrigerator etc. Your 15-min calculation on those days when AC is not used should provide you the info. For example, if microwave was used every morning during breakfast time like 7am, then look around that time window and you can see how much this adds to some baseline use.

(** circulate mode is a term used in my thermostat. It just cycles the fan, eg., 10-min ON and 10-min OFF.)

As example, my baseline use is like 300-400W for running a few porch lights, router/wifi, etc during the time period between midnight and 4am. In the morning, when I use the microwave, I can see an additional 1500W spike within a 15-min window. A new refrigerator uses maybe 100W-200W. Someone using their hair dryer would result in another 1000-2000W spike.

Note that an aggregate (microwave + hair dryer + router/lights/etc) of 4kW (as example) for a 15min interval and zero for the remaining 45min means 1kWh of energy, ie., 4 x (15/60).

3) partial backup configuration?
Need a sub panel with critical loads or some automated means of load shedding, eg., disable AC circuits.

4) without solar?
If not planning to have solar panels, then a multi-day outage would mean no charging option once battery capacity has been used. Even with solar panels, there might not be sufficient excess solar to charge batteries. For example, multiple cloudy days (=not much solar production) or hot days (=solar is mostly consumed for home load with ACs).

5) evaluate installed $/kWh for your storage capacity
Do an apples-to-apples comparison, eg., installed cost for (y) kWh energy storage capacity. Also, consider up time in evaluating cost. For example, if 1 PW, and it fails so no backup until repairs are done…..vs having 2 or 3 allowing for 1 unit to be down as worst case.

(Fyi- I have 3 PWs)

More aspects to think through….but, will add later if I think of something useful to add.
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by ExtraCool »

From the power load info in the 15-min interval data, find the max for the days without AC use. This should inform you of the continuous power that the battery storage system needs to support. A single PW, for example, can support 5kW continuous power. Likewise, 2 PWs can support 10kW continuous power. Check battery data sheet for whichever battery systems you want to evaluate.

With AC use, you will need the LRA value. You can find this in a label on the condenser unit. This is relevant to understand the peak power over a very short sub-second interval. Check battery specs - for example, see for PW there is mention of 106amps for LRA - https://www.tesla.com/support/energy/po ... wall-works

(Edited acronym - LRA)
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by iamlucky13 »

need403bhelp wrote: Sun Jul 07, 2024 9:49 pm (i) During natural disasters, people stop being polite. We do live next to a not quite upscale apartment complex turned AirBNB rental. Our backyard faces right into their parking lot with a wood fence as separator. If I left a generator running there after a hurricane, I don't think it is out of the question it would get stolen.
240V generators capable of running a central AC system aren't something you hop over a fence with. They'd have to wheel it through a gate. It should also be possible to come up with a way to apply a heavy duty bike lock to it when in use if you have serious concerns.

Keep in mind you will need a generator transfer switch and panel installed. But any integrated backup solution requires some wiring, including a disconnect.
(ii) Getting gas during a natural disaster would also likely be difficult to power such a generator. Storing gas in a garage seems somewhat risky.
Storing gas in a garage is a very normal thing to do, both inside the cars that get parked in the garage, or inside portable cans for use with lawn equipment. Do be aware that gas needs to get rotated, as it goes bad over time. But if you do not want to do this, then a gasoline-powered generator is not a good option - waiting until a major outage to get fuel simply leaves too much risk that you won't be able to get fuel when you need it.

If you have natural gas available, that might also be an option. Even some portable generators are designed to be converted to run on natural gas.

Gas-powered generators should be test run periodically to make sure they are in good condition, and then stored without fuel, so there is some periodic maintenance. On a positive note, a sub-$2000 portable generator and 10 gallons of fuel can provide as much total energy as the $17,500 pair of Powerwalls you're considering would store.

Where Powerwall or similar home energy storage systems would be most appealing are areas where there is a steep time-of-use premium for peak hours, allowing them to create value every day, or potentially when paired with a home solar system, if you want to be able to last through long duration outages. However, they should be low maintenance, and pretty seamless in operation, and silent.

Regarding running the refrigerator during an evacuation scenario, I personally would not pursue that very aggressively. Obviously you wouldn't leave a generator running unattended, but seeking battery capacity to keep it running long term could easily exceed the value of the food that would be lost. On the other hand, if you have enough battery capacity to run the air conditioner for a day or more if you are home, you have enough to run just the refrigerator for probably over a week.
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snackdog
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by snackdog »

The instantaneous amperage on compressors can be large. I have a few 4 ton heat pumps which run at 15 amps but can be as much as 83 amps on startup (locked rotor or LR amps). If just two should happen to start simultaneously, I'd be looking at 166 amps on HVAC alone.
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lazydavid
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Re: Whole house ELECTRIC backup - PowerWall? Alternatives?

Post by lazydavid »

snackdog wrote: Tue Jul 09, 2024 12:47 am The instantaneous amperage on compressors can be large. I have a few 4 ton heat pumps which run at 15 amps but can be as much as 83 amps on startup (locked rotor or LR amps). If just two should happen to start simultaneously, I'd be looking at 166 amps on HVAC alone.
You can dramatically reduce this for a few hundred dollars by installing a soft start on the outdoor units. Every unit will vary, but you should be able to get the peak inrush down into the mid 20A range per unit.
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