Solar Install w/ SolarCity

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unclescrooge
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Re: Solar Install w/ SolarCity

Post by unclescrooge » Mon Sep 09, 2019 8:48 am

SmallCityDave wrote:
Sun Sep 08, 2019 8:29 pm
unclescrooge wrote:
Sun Sep 08, 2019 7:19 pm
SmallCityDave wrote:
Sun Sep 08, 2019 6:47 pm
That's a heck of a system. We got solar last week our intent was financial not political nor was it to save the planet.

Here is a quick snapshot of our system and the finances behind it, I won't go into too much detail. Our system is rated at 7.2kw plus they added the .8kw system (home built) that we already had so 8kw combined for $15,800 - after taxes credits it should be $10k.

Last week our utility company charged us $.108kwh and that will go down to $.08kwh in November (because we are on solar) plus they will pay $.064 when we export that price will be locked in for 10 years. I was hoping that the system would pay for itself in 10 years but looking at all thee numbers I'm hopeful it will be less.
What were your previous utility bills?
$180 per month using 1350kw per month , all electric home.
So shouldn't your pay back be just under 5 years?

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SmallCityDave
Posts: 152
Joined: Thu Feb 21, 2019 10:04 am

Re: Solar Install w/ SolarCity

Post by SmallCityDave » Mon Sep 09, 2019 9:37 am

unclescrooge wrote:
Mon Sep 09, 2019 8:48 am
SmallCityDave wrote:
Sun Sep 08, 2019 8:29 pm
unclescrooge wrote:
Sun Sep 08, 2019 7:19 pm
SmallCityDave wrote:
Sun Sep 08, 2019 6:47 pm
That's a heck of a system. We got solar last week our intent was financial not political nor was it to save the planet.

Here is a quick snapshot of our system and the finances behind it, I won't go into too much detail. Our system is rated at 7.2kw plus they added the .8kw system (home built) that we already had so 8kw combined for $15,800 - after taxes credits it should be $10k.

Last week our utility company charged us $.108kwh and that will go down to $.08kwh in November (because we are on solar) plus they will pay $.064 when we export that price will be locked in for 10 years. I was hoping that the system would pay for itself in 10 years but looking at all thee numbers I'm hopeful it will be less.
What were your previous utility bills?
$180 per month using 1350kw per month , all electric home.
So shouldn't your pay back be just under 5 years?
I think that 9 years is more realistic.

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unclescrooge
Posts: 3711
Joined: Thu Jun 07, 2012 7:00 pm

Re: Solar Install w/ SolarCity

Post by unclescrooge » Mon Sep 09, 2019 2:18 pm

SmallCityDave wrote:
Mon Sep 09, 2019 9:37 am
unclescrooge wrote:
Mon Sep 09, 2019 8:48 am
SmallCityDave wrote:
Sun Sep 08, 2019 8:29 pm
unclescrooge wrote:
Sun Sep 08, 2019 7:19 pm
SmallCityDave wrote:
Sun Sep 08, 2019 6:47 pm
That's a heck of a system. We got solar last week our intent was financial not political nor was it to save the planet.

Here is a quick snapshot of our system and the finances behind it, I won't go into too much detail. Our system is rated at 7.2kw plus they added the .8kw system (home built) that we already had so 8kw combined for $15,800 - after taxes credits it should be $10k.

Last week our utility company charged us $.108kwh and that will go down to $.08kwh in November (because we are on solar) plus they will pay $.064 when we export that price will be locked in for 10 years. I was hoping that the system would pay for itself in 10 years but looking at all thee numbers I'm hopeful it will be less.
What were your previous utility bills?
$180 per month using 1350kw per month , all electric home.
So shouldn't your pay back be just under 5 years?
I think that 9 years is more realistic.
$10k/(180*12)=4.76
Unless you're not producing enough electricity to offset your entire bill

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SmallCityDave
Posts: 152
Joined: Thu Feb 21, 2019 10:04 am

Re: Solar Install w/ SolarCity

Post by SmallCityDave » Mon Sep 09, 2019 5:54 pm

unclescrooge wrote:
Mon Sep 09, 2019 2:18 pm

$10k/(180*12)=4.76
Unless you're not producing enough electricity to offset your entire bill
No it won't, my intent was to reduce the bill to $100.

TravelforFun
Posts: 1865
Joined: Tue Dec 04, 2012 11:05 pm

Re: Solar Install w/ SolarCity

Post by TravelforFun » Mon Sep 09, 2019 6:09 pm

emoore wrote:
Sat Sep 15, 2018 8:33 pm
Congrats. We are probably doing the same. Will have Tesla install panels. Don’t have an EV yet but will get one soon. You should be proud and excited with the difference you are making.
Congrats to you too!

TravelforFun

Topic Author
mmcmonster
Posts: 360
Joined: Sun Jan 12, 2014 1:18 pm

Re: Solar Install w/ SolarCity

Post by mmcmonster » Tue Sep 10, 2019 5:09 am

Dilbydog wrote:
Sun Sep 08, 2019 1:27 pm
OP... I’m very interested to see what your actual annual generation numbers look like. With the majority of your modules facing westward, I would think your production would be less than what Solar City ‘estimated’.

Did they install micro-inverters or string inverters for your system?

The power wall setup, does that feed your entire home? (IE every outlet and fixture) My understanding is that the power wall system would need to be hooked up to a sub panel with an ATS to prevent the battery system from back feeding the grid during an outage.
Aug: 10.1 kWh (for the purpose of this thread, I included the 1 day in August in my September numbers)
Sep: 1455.1 kWh
Oct: 1525.2
Nov: 1005.4
Dec: 907.6
Jan: 1131
Feb: 1417
Mar: 2103
Apr: 2017
May: 2099
Jun: 2485
Jul: 2582
Aug: 2442

The panels are stringed on the roof and connected to two inverters. The two inverters feed into a panel that connects to the batteries and sends power to a second panel. That second panel gets the incoming power line from the electric company and the incoming line from the solar+batteries panel and feeds the house main panel. While all of this is rated to be outside the house (including the batteries), I put it all in the basement, hopefully to decrease wear and tear from the weather.

The second panel determines if there's no power and (if so) will draw from the batteries and solar panel. Don't think you can do this without a battery backup system, otherwise you would have a brownout every time there was a cloud overhead. :annoyed

My whole house is connected. I need three batteries to be able to draw fast enough to charge the car during an outage. Of course, I cannot fully charge my car (at night) during an outage as the car battery is bigger than my house batteries.

Nearly A Moose
Posts: 1000
Joined: Fri Apr 22, 2016 5:28 pm

Re: Solar Install w/ SolarCity

Post by Nearly A Moose » Tue Sep 10, 2019 8:33 pm

Thanks for the write up and update - it’s always really interesting to see how the math plays out here. Would love to have been in a position to do this before the tax subsidy started dropping, but oh well.

A question, purely out of curiosity: you keep mentioning charging your car all night drains the PowerWalls because the cars battery is larger than the walls. But if you’re driving ~60 miles a day, that’s only like 1/4 of the car’s range, right? So aren’t you actually getting performance out of the system?
Pardon typos, I'm probably using my fat thumbs on a tiny phone.

njdealguy
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Joined: Wed Jul 26, 2017 8:15 am

Re: Solar Install w/ SolarCity

Post by njdealguy » Tue Sep 10, 2019 9:25 pm

To OP just wondering what the benefit is to having Tesla powerwall or any batteries in a state with full net metering where grid charges same amount at all times as in no time of use, besides support during occasional power outages? I myself just signed on a couple weeks ago for a 8.2kw panel system in NJ and hopefully including cost of the roof at 33k before tax credit hope to break even in 6 or so years.

Topic Author
mmcmonster
Posts: 360
Joined: Sun Jan 12, 2014 1:18 pm

Re: Solar Install w/ SolarCity

Post by mmcmonster » Thu Sep 12, 2019 5:26 am

Nearly A Moose wrote:
Tue Sep 10, 2019 8:33 pm
A question, purely out of curiosity: you keep mentioning charging your car all night drains the PowerWalls because the cars battery is larger than the walls. But if you’re driving ~60 miles a day, that’s only like 1/4 of the car’s range, right? So aren’t you actually getting performance out of the system?
Good point. At first I was charging the car back up to full with the home battery.

The system has a phone app, in which you can keep a set percentage of battery power reserved just for power outages. I had it set to 10%.

My wife got into a panic (WHAT IF WE HAVE A POWER OUTAGE THAT LASTS ALL NIGHT???) and increased the power reserve to 50% and sometimes manually adjusts it (much higher) based on the weather.

I've learned to not touch it. Safer on the marriage. :beer

FrugalConservative
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Joined: Thu Aug 17, 2017 9:44 am

Re: Solar Install w/ SolarCity

Post by FrugalConservative » Thu Sep 12, 2019 7:11 am

delete
Last edited by FrugalConservative on Thu Sep 12, 2019 7:13 am, edited 1 time in total.

FrugalConservative
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Joined: Thu Aug 17, 2017 9:44 am

Re: Solar Install w/ SolarCity

Post by FrugalConservative » Thu Sep 12, 2019 7:12 am

16 year payback ( would be higher if you didnt factor in the generator cost as well), $76K for the system.Seems like insanity to me.

Valuethinker
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Joined: Fri May 11, 2007 11:07 am

Re: Solar Install w/ SolarCity

Post by Valuethinker » Thu Sep 12, 2019 12:13 pm

mmcmonster wrote:
Thu Sep 12, 2019 5:26 am
Nearly A Moose wrote:
Tue Sep 10, 2019 8:33 pm
A question, purely out of curiosity: you keep mentioning charging your car all night drains the PowerWalls because the cars battery is larger than the walls. But if you’re driving ~60 miles a day, that’s only like 1/4 of the car’s range, right? So aren’t you actually getting performance out of the system?
Good point. At first I was charging the car back up to full with the home battery.

The system has a phone app, in which you can keep a set percentage of battery power reserved just for power outages. I had it set to 10%.

My wife got into a panic (WHAT IF WE HAVE A POWER OUTAGE THAT LASTS ALL NIGHT???) and increased the power reserve to 50% and sometimes manually adjusts it (much higher) based on the weather.

I've learned to not touch it. Safer on the marriage. :beer
I believe I am right that for maximising the lifespan of Lithium Ion batteries, you have to keep charge never above 80% and never below 20%? I think the Toyota Prius is optimised that way?

harikaried
Posts: 1270
Joined: Fri Mar 09, 2012 3:47 pm

Re: Solar Install w/ SolarCity

Post by harikaried » Thu Sep 12, 2019 12:48 pm

njdealguy wrote:
Tue Sep 10, 2019 9:25 pm
just wondering what the benefit is to having Tesla powerwall or any batteries in a state with full net metering
Yeah, we've been wondering the same now that we're looking at sizing up how much solar to buy -- although we have the option of switching to Time of Use + Net Metering billing where summer time peak hours is ~5x the standard rate while other times are ~⅓ discount from standard rate. What we're currently planning is to have the solar panels generate enough kW to cover any peak hour usage, and any excess, e.g., times we aren't even running A/C, we get credited at the more expensive peak electricity rates using the grid like a battery, so then at night, we pull from the "grid battery" at the cheaper rate thus getting roughly 6x kWh for each we put in earlier in the day (or from previous days).

So with this net metering, indeed it doesn't seem cost effective to store electricity locally.

I did ask a Tesla solar representative why Powerwall, and the response was the battery would allow pulling from it during peak time so that all of the solar to be sold to the grid during peak time. But even then, at best if the whole battery capacity was discharged entirely every day during peak hours thus maximizing the peak hour credits, it wouldn't exceed the cost of adding the battery in the first place over 10 years.

emoore
Posts: 542
Joined: Mon Mar 04, 2013 8:16 pm

Re: Solar Install w/ SolarCity

Post by emoore » Thu Sep 12, 2019 1:25 pm

Valuethinker wrote:
Thu Sep 12, 2019 12:13 pm
mmcmonster wrote:
Thu Sep 12, 2019 5:26 am
Nearly A Moose wrote:
Tue Sep 10, 2019 8:33 pm
A question, purely out of curiosity: you keep mentioning charging your car all night drains the PowerWalls because the cars battery is larger than the walls. But if you’re driving ~60 miles a day, that’s only like 1/4 of the car’s range, right? So aren’t you actually getting performance out of the system?
Good point. At first I was charging the car back up to full with the home battery.

The system has a phone app, in which you can keep a set percentage of battery power reserved just for power outages. I had it set to 10%.

My wife got into a panic (WHAT IF WE HAVE A POWER OUTAGE THAT LASTS ALL NIGHT???) and increased the power reserve to 50% and sometimes manually adjusts it (much higher) based on the weather.

I've learned to not touch it. Safer on the marriage. :beer
I believe I am right that for maximising the lifespan of Lithium Ion batteries, you have to keep charge never above 80% and never below 20%? I think the Toyota Prius is optimised that way?
That's the typical range that EV car makers have stated. Although I don't think the Prius has lithium ion batteries.

emoore
Posts: 542
Joined: Mon Mar 04, 2013 8:16 pm

Re: Solar Install w/ SolarCity

Post by emoore » Thu Sep 12, 2019 1:28 pm

harikaried wrote:
Thu Sep 12, 2019 12:48 pm
njdealguy wrote:
Tue Sep 10, 2019 9:25 pm
just wondering what the benefit is to having Tesla powerwall or any batteries in a state with full net metering
Yeah, we've been wondering the same now that we're looking at sizing up how much solar to buy -- although we have the option of switching to Time of Use + Net Metering billing where summer time peak hours is ~5x the standard rate while other times are ~⅓ discount from standard rate. What we're currently planning is to have the solar panels generate enough kW to cover any peak hour usage, and any excess, e.g., times we aren't even running A/C, we get credited at the more expensive peak electricity rates using the grid like a battery, so then at night, we pull from the "grid battery" at the cheaper rate thus getting roughly 6x kWh for each we put in earlier in the day (or from previous days).

So with this net metering, indeed it doesn't seem cost effective to store electricity locally.

I did ask a Tesla solar representative why Powerwall, and the response was the battery would allow pulling from it during peak time so that all of the solar to be sold to the grid during peak time. But even then, at best if the whole battery capacity was discharged entirely every day during peak hours thus maximizing the peak hour credits, it wouldn't exceed the cost of adding the battery in the first place over 10 years.
I don't think the batteries would make sense financially. They are the most valuable for backup in case of power outages. Cheaper to run than a natural gas generator.

Topic Author
mmcmonster
Posts: 360
Joined: Sun Jan 12, 2014 1:18 pm

Re: Solar Install w/ SolarCity

Post by mmcmonster » Fri Sep 13, 2019 5:49 am

emoore wrote:
Thu Sep 12, 2019 1:28 pm
harikaried wrote:
Thu Sep 12, 2019 12:48 pm
njdealguy wrote:
Tue Sep 10, 2019 9:25 pm
just wondering what the benefit is to having Tesla powerwall or any batteries in a state with full net metering
Yeah, we've been wondering the same now that we're looking at sizing up how much solar to buy -- although we have the option of switching to Time of Use + Net Metering billing where summer time peak hours is ~5x the standard rate while other times are ~⅓ discount from standard rate. What we're currently planning is to have the solar panels generate enough kW to cover any peak hour usage, and any excess, e.g., times we aren't even running A/C, we get credited at the more expensive peak electricity rates using the grid like a battery, so then at night, we pull from the "grid battery" at the cheaper rate thus getting roughly 6x kWh for each we put in earlier in the day (or from previous days).

So with this net metering, indeed it doesn't seem cost effective to store electricity locally.

I did ask a Tesla solar representative why Powerwall, and the response was the battery would allow pulling from it during peak time so that all of the solar to be sold to the grid during peak time. But even then, at best if the whole battery capacity was discharged entirely every day during peak hours thus maximizing the peak hour credits, it wouldn't exceed the cost of adding the battery in the first place over 10 years.
I don't think the batteries would make sense financially. They are the most valuable for backup in case of power outages. Cheaper to run than a natural gas generator.
Agree. I got the batteries instead of a gas generator. We get an average of one serious (>1 hour) blackout a year. The community was hit somewhat hard with Hurricane Sandy, where we lost power for a couple days, and my wife insisted we look into generators at the time. I think the batteries are a much better approach for me (I'm a set-it and forget-it guy and don't want to worry about maintenance of a generator), even at a bit of a premium.

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