Electric Water Heater vs Tankless Electric (space limitations)

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SurferLife
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Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

I have previously read through many of the water heater threads and decided we'd go with a tank water heater in replacing our current one. But as things evolved, the problem became more complex and now we are at a cross roads.

We currently have a 50 gal electric (non-heat pump) water heater that is on its last legs and we are a family of 4 with 2 young kids (5 and 7). We have had a few occasions when our 50 gal didn’t provide enough hot water, and I imagine that as our kids get older this problem will only get worse. I had wanted to replace it with an 80 gal, electric, heat pump water heater but have discovered that we do not have a high enough ceiling in our basement to make that happen. I resigned to a 65 gal electric, heat pump water heater, but being that we are in a remote location in Hawaii, Home Depot can not get one here. The local plumbing supply can get a 65 gal Bradford White one which is around $3,000, nearly a full $1,000 more than an 80 gallon Reem one at Home Depot. Of course, we can always replace it with a 50 gal electric, heat pump water heater, but I worry that it won’t be sufficient.

Adding to the costs, the water heater currently sits on a concrete riser than needs to be jackhammered out to fit the 65gal, and so of course with that labor included, I started thinking, should we just go to a tankless electric water heater? My biggest concern is the annual maintenance costs and the efficiencies of the tankless. We have the highest electricity prices in the U.S., but we are installing a 7.5kw Solar System in the next few months with battery backup.

Curious as to what other Bogleheads would do in this situation.
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galawdawg
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by galawdawg »

Consider sticking with a new 50 gallon conventional water heater and adding a thermostatic mixing valve at the tank outlet, such as this: https://www.cashacme.com/us/en/thermost ... ooster-pro

They work well in my experience and would seem ideal for your situation.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Californiastate »

What are the amperage requirements for the tankless you’re liking at?
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

Californiastate wrote: Mon Sep 19, 2022 4:30 pm What are the amperage requirements for the tankless you’re liking at?
It's looking like either 113 or 150 amps.

We are also in the middle of getting the whole house rewired, so adding a new line for the tankless would be very easy, though it would be an additional cost.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Californiastate »

SurferLife wrote: Mon Sep 19, 2022 7:02 pm
Californiastate wrote: Mon Sep 19, 2022 4:30 pm What are the amperage requirements for the tankless you’re liking at?
It's looking like either 113 or 150 amps.

We are also in the middle of getting the whole house rewired, so adding a new line for the tankless would be very easy, though it would be an additional cost.
You'll need to pass this by your electrician. I don't see it working without a 400 amp service.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by mortfree »

Can you get two 50 gallons?
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Bogle Millennial »

You definitely should run this by your electrician doing your house rewiring. I wanted to go tankless when we replaced our traditional electric tank water heater, but we would have had to increase our electric feed from the utility up to 400 amps currently at 250 amps. With our house being all-electric, we already run high on electricity feed in the additional cost of running a higher amperage from the utility became a major negative on going thankless.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by femur »

My wife and I just built an all-electric house in Texas this year. We went with a Rheem electric tankless water heater from Home depot. It was ~$500. It is the 27kw version (draws 113amps max). We are VERY happy with it. We have run 2 showers at the same time on multiple occasions with no issue.

Edit: I have 200amp electric service
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by suemarkp »

Electric tankless water heaters usually need multiple circuits (typically two to three 40 or 50 amp 240V circuits). It adds a big chunk to your load calculation. Definitely tell the electrician to make sure you have panel space, panel amp rating, and service amps to cover it. If thinking an electric car, that is another big swinger to mention.

You could just install two 40 or 50 gallon conventional water heaters (heat pump type or pure resistance, or one of each). They may be cheaper, easier for your supply chain, and won't be as bad of a hit on the electrical service (two 30A 240V circuits).
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

femur wrote: Mon Sep 19, 2022 8:35 pm My wife and I just built an all-electric house in Texas this year. We went with a Rheem electric tankless water heater from Home depot. It was ~$500. It is the 27kw version (draws 113amps max). We are VERY happy with it. We have run 2 showers at the same time on multiple occasions with no issue.

Edit: I have 200amp electric service
That’s good to know. We have 200 amp service.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

suemarkp wrote: Mon Sep 19, 2022 10:15 pm Electric tankless water heaters usually need multiple circuits (typically two to three 40 or 50 amp 240V circuits). It adds a big chunk to your load calculation. Definitely tell the electrician to make sure you have panel space, panel amp rating, and service amps to cover it. If thinking an electric car, that is another big swinger to mention.

You could just install two 40 or 50 gallon conventional water heaters (heat pump type or pure resistance, or one of each). They may be cheaper, easier for your supply chain, and won't be as bad of a hit on the electrical service (two 30A 240V circuits).
Now we hadn’t considered doing two 50 gallon water heaters. Perhaps we could just go with a 50 gallon now and then when the kids get older and it’s more of a problem, add a second 50 gallon.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

mortfree wrote: Mon Sep 19, 2022 8:19 pm Can you get two 50 gallons?
It would take up more space than we want, but it’s a possibility.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Valuethinker »

SurferLife wrote: Mon Sep 19, 2022 3:48 pm I have previously read through many of the water heater threads and decided we'd go with a tank water heater in replacing our current one. But as things evolved, the problem became more complex and now we are at a cross roads.

We currently have a 50 gal electric (non-heat pump) water heater that is on its last legs and we are a family of 4 with 2 young kids (5 and 7). We have had a few occasions when our 50 gal didn’t provide enough hot water, and I imagine that as our kids get older this problem will only get worse. I had wanted to replace it with an 80 gal, electric, heat pump water heater but have discovered that we do not have a high enough ceiling in our basement to make that happen. I resigned to a 65 gal electric, heat pump water heater, but being that we are in a remote location in Hawaii, Home Depot can not get one here. The local plumbing supply can get a 65 gal Bradford White one which is around $3,000, nearly a full $1,000 more than an 80 gallon Reem one at Home Depot. Of course, we can always replace it with a 50 gal electric, heat pump water heater, but I worry that it won’t be sufficient.

Adding to the costs, the water heater currently sits on a concrete riser than needs to be jackhammered out to fit the 65gal, and so of course with that labor included, I started thinking, should we just go to a tankless electric water heater? My biggest concern is the annual maintenance costs and the efficiencies of the tankless. We have the highest electricity prices in the U.S., but we are installing a 7.5kw Solar System in the next few months with battery backup.

Curious as to what other Bogleheads would do in this situation.
In England we have what is called a "thermal store" and your PV setup got me to thinking.

Your hot water tank (aka thermal store) would allow you to "bank" periods of high solar output.

I am not sure how this might fit in with your situation (if at all) but it would tilt me towards continuing to have a water tank.

Tankless systems work well with natural gas but I am not familiar with electric ones. Heat pump water heater?
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Valuethinker »

SurferLife wrote: Mon Sep 19, 2022 11:16 pm
suemarkp wrote: Mon Sep 19, 2022 10:15 pm Electric tankless water heaters usually need multiple circuits (typically two to three 40 or 50 amp 240V circuits). It adds a big chunk to your load calculation. Definitely tell the electrician to make sure you have panel space, panel amp rating, and service amps to cover it. If thinking an electric car, that is another big swinger to mention.

You could just install two 40 or 50 gallon conventional water heaters (heat pump type or pure resistance, or one of each). They may be cheaper, easier for your supply chain, and won't be as bad of a hit on the electrical service (two 30A 240V circuits).
Now we hadn’t considered doing two 50 gallon water heaters. Perhaps we could just go with a 50 gallon now and then when the kids get older and it’s more of a problem, add a second 50 gallon.
It sounds like the simplest solution. Yes you probably need more than a 50 gallon tank. Given height requirements, plan to expand. I doubt a plumber would have much difficulty with setting it up and maintenance. And that, tbh, is as big a consideration as anything else. Given where you live and that you probably don't have a lot of choices.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Valuethinker »

SurferLife wrote: Mon Sep 19, 2022 3:48 pm I have previously read through many of the water heater threads and decided we'd go with a tank water heater in replacing our current one. But as things evolved, the problem became more complex and now we are at a cross roads.

We currently have a 50 gal electric (non-heat pump) water heater that is on its last legs and we are a family of 4 with 2 young kids (5 and 7). We have had a few occasions when our 50 gal didn’t provide enough hot water, and I imagine that as our kids get older this problem will only get worse. I had wanted to replace it with an 80 gal, electric, heat pump water heater but have discovered that we do not have a high enough ceiling in our basement to make that happen. I resigned to a 65 gal electric, heat pump water heater, but being that we are in a remote location in Hawaii, Home Depot can not get one here. The local plumbing supply can get a 65 gal Bradford White one which is around $3,000, nearly a full $1,000 more than an 80 gallon Reem one at Home Depot. Of course, we can always replace it with a 50 gal electric, heat pump water heater, but I worry that it won’t be sufficient.

Adding to the costs, the water heater currently sits on a concrete riser than needs to be jackhammered out to fit the 65gal, and so of course with that labor included, I started thinking, should we just go to a tankless electric water heater? My biggest concern is the annual maintenance costs and the efficiencies of the tankless. We have the highest electricity prices in the U.S., but we are installing a 7.5kw Solar System in the next few months with battery backup.

Curious as to what other Bogleheads would do in this situation.
"Obvious" point. If you have a tankless, then if you want electricity at a time of day (typically after sundown) when electricity prices are high, you are going to pay through the nose for it. Assuming Time of Use tariffs. And you won't be able to use your own solar PV for hot water except in daytime.

That last factor (can't use own PV) would definitely make me want to keep a water tank.

I am a big fan of Heat Pump water heaters, however depending on how they vent they make the surrounding air colder, (which may not be of concern in Hawaii).
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by lthenderson »

SurferLife wrote: Mon Sep 19, 2022 3:48 pm Curious as to what other Bogleheads would do in this situation.
Family of five with two kids older than yours and a 50 gallon tank that still serves us well. My recommendation would be just to study your hot water usage habits and make small tweaks in usage rather than go to all the expense of providing hot water 24 hours a day 7 days a week in larger quantities for those few occasions you didn't have enough hot water.

We stagger our showers. With modern restricted shower heads, two people can easily take long showers back to back without running out of hot water and three if they are quick. Wait one hour and then two more can shower. We give the kids the primetime shower usage and us adults take them later in the evening or early in the morning while they are in bed. Run hot water appliances like dishwasher or clothes washer at other times of the day. The only time I remember running out of hot water in the last 20 years was when my BIL and family (also 5) were staying with our family for a couple of weeks. Staggering ten people took a little more time and planning.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by TomatoTomahto »

Valuethinker wrote: Tue Sep 20, 2022 2:57 am I am a big fan of Heat Pump water heaters, however depending on how they vent they make the surrounding air colder, (which may not be of concern in Hawaii).
I am also a heat pump fan (3 ground sourced and 2 air sourced heat pumps at our house). However, OP is space constrained and a heat pump water heater is not fit for purpose in that circumstance. I threw mine out and replaced it with a fiberglass tank model.
I get the FI part but not the RE part of FIRE.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Bengineer »

OP, what does "on its last legs" mean?

We have a thermostatic mixing valve on our tank electric water heater. It mixes the 150d.F. water down to ~120d.F. or so.

With sufficient tank capacity and solar, you could put the water heater(s) on a timer/controller to use the PV to heat the water during the day for use later. I'd think that would be a win with your rates.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by ncbill »

If OP is putting in a solar electric system they've got enough sunshine to put in solar water heating, e.g. a thermo-syphoning system.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by iamblessed »

lthenderson wrote: Tue Sep 20, 2022 6:13 am
SurferLife wrote: Mon Sep 19, 2022 3:48 pm Curious as to what other Bogleheads would do in this situation.
Family of five with two kids older than yours and a 50 gallon tank that still serves us well. My recommendation would be just to study your hot water usage habits and make small tweaks in usage rather than go to all the expense of providing hot water 24 hours a day 7 days a week in larger quantities for those few occasions you didn't have enough hot water.

We stagger our showers. With modern restricted shower heads, two people can easily take long showers back to back without running out of hot water and three if they are quick. Wait one hour and then two more can shower. We give the kids the primetime shower usage and us adults take them later in the evening or early in the morning while they are in bed. Run hot water appliances like dishwasher or clothes washer at other times of the day. The only time I remember running out of hot water in the last 20 years was when my BIL and family (also 5) were staying with our family for a couple of weeks. Staggering ten people took a little more time and planning.
Very true we had company once and did six showers with a 40 gallon tank.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Rattlesnake »

Due to the electric requirements, we went with a LP Rinnai tankless hot water heater for our cottage in Canada (we have 100 amp service there).... Not sure if LP is an option for you.... Just my $0.02....
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by bostonenginerd »

FWIW, we have a 50gal Rheem HPWH for our family of four and have not had any issues with a lack of hot water. We do use a low flow shower head, but run dishes and laundry with hot on occasion.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

Rattlesnake wrote: Tue Sep 20, 2022 8:16 am Due to the electric requirements, we went with a LP Rinnai tankless hot water heater for our cottage in Canada (we have 100 amp service there).... Not sure if LP is an option for you.... Just my $0.02....
Gas is not an option.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by ClassII »

lthenderson wrote: Tue Sep 20, 2022 6:13 am
SurferLife wrote: Mon Sep 19, 2022 3:48 pm Curious as to what other Bogleheads would do in this situation.
Family of five with two kids older than yours and a 50 gallon tank that still serves us well. My recommendation would be just to study your hot water usage habits and make small tweaks in usage rather than go to all the expense of providing hot water 24 hours a day 7 days a week in larger quantities for those few occasions you didn't have enough hot water.
^This. All this talk of dual 50 gallon tanks, major house electrical upgrades for tankless etc. seems to miss a much simpler solution. 50 gallons is a LOT of hot water. Seems to me that there may be a usage issue here.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Valuethinker »

SurferLife wrote: Tue Sep 20, 2022 9:56 am
Rattlesnake wrote: Tue Sep 20, 2022 8:16 am Due to the electric requirements, we went with a LP Rinnai tankless hot water heater for our cottage in Canada (we have 100 amp service there).... Not sure if LP is an option for you.... Just my $0.02....
Gas is not an option.
(I would imagine LPG/ propane costs as much (per unit energy) as oil heating? And of course the price swings make it totally unpredictable).
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by galawdawg »

Bengineer wrote: Tue Sep 20, 2022 6:16 am OP, what does "on its last legs" mean?

We have a thermostatic mixing valve on our tank electric water heater. It mixes the 150d.F. water down to ~120d.F. or so.
As I recommended early in the thread, that seems like a good solution for the OP's situation. Even ignoring recovery, a fifty gallon tank heated to 150° will produce over sixty-two gallons of water at 120° when a thermostatic mixing valve is used with the system.

Using 1.8 gpm shower heads, the maximum flow rate in Hawaii, even if the tank did not heat any additional water when the first shower begins, there would be enough water for thirty-six minutes at 120°. That's certainly sufficient for a family of four.

And since the water heater continues to produce hot water during usage, you get more than that. For example, the least expensive Rheem fifty gal electric at Home Depot will produce sixty-one gallons in the first hour. Heat the water to 150°, add the thermostatic mixing valve, and now you have over seventy-five gallons of 120° water in the first hour or enough for forty-two minutes of showering in the first sixty minutes.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

ncbill wrote: Tue Sep 20, 2022 7:17 am If OP is putting in a solar electric system they've got enough sunshine to put in solar water heating, e.g. a thermo-syphoning system.
We did consider this but decided against it in favor of more PV panels; we have roof space limitations. Also, the cost was around 10k.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

galawdawg wrote: Tue Sep 20, 2022 11:40 am
Bengineer wrote: Tue Sep 20, 2022 6:16 am OP, what does "on its last legs" mean?

We have a thermostatic mixing valve on our tank electric water heater. It mixes the 150d.F. water down to ~120d.F. or so.
As I recommended early in the thread, that seems like a good solution for the OP's situation. Even ignoring recovery, a fifty gallon tank heated to 150° will produce over sixty-two gallons of water at 120° when a thermostatic mixing valve is used with the system.

Using 1.8 gpm shower heads, the maximum flow rate in Hawaii, even if the tank did not heat any additional water when the first shower begins, there would be enough water for thirty-six minutes at 120°. That's certainly sufficient for a family of four.

And since the water heater continues to produce hot water during usage, you get more than that. For example, the least expensive Rheem fifty gal electric at Home Depot will produce sixty-one gallons in the first hour. Heat the water to 150°, add the thermostatic mixing valve, and now you have over seventy-five gallons of 120° water in the first hour or enough for forty-two minutes of showering in the first sixty minutes.
So, I have been looking at the thermostatic mixing valve you linked to, and I'm not quite sure I understand it fully, but sort of understand the concept. Is this a new technology and if not, how long has it been around? Will this be a problem for future plumber maintenance where they have no idea what is attached to the water heater? Does it require any maintenance? Also, is it compatible with the heat pump water heaters or do I need a straight up electric? I do feel that we must go to a heat pump water heater. When we left the house for a month and left the water heater on, our electric bill was nearly $300, and nobody was even home that month.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by galawdawg »

SurferLife wrote: Tue Sep 20, 2022 11:47 am
galawdawg wrote: Tue Sep 20, 2022 11:40 am
Bengineer wrote: Tue Sep 20, 2022 6:16 am OP, what does "on its last legs" mean?

We have a thermostatic mixing valve on our tank electric water heater. It mixes the 150d.F. water down to ~120d.F. or so.
As I recommended early in the thread, that seems like a good solution for the OP's situation. Even ignoring recovery, a fifty gallon tank heated to 150° will produce over sixty-two gallons of water at 120° when a thermostatic mixing valve is used with the system.

Using 1.8 gpm shower heads, the maximum flow rate in Hawaii, even if the tank did not heat any additional water when the first shower begins, there would be enough water for thirty-six minutes at 120°. That's certainly sufficient for a family of four.

And since the water heater continues to produce hot water during usage, you get more than that. For example, the least expensive Rheem fifty gal electric at Home Depot will produce sixty-one gallons in the first hour. Heat the water to 150°, add the thermostatic mixing valve, and now you have over seventy-five gallons of 120° water in the first hour or enough for forty-two minutes of showering in the first sixty minutes.
So, I have been looking at the thermostatic mixing valve you linked to, and I'm not quite sure I understand it fully, but sort of understand the concept. Is this a new technology and if not, how long has it been around? Will this be a problem for future plumber maintenance where they have no idea what is attached to the water heater? Does it require any maintenance? Also, is it compatible with the heat pump water heaters or do I need a straight up electric? I do feel that we must go to a heat pump water heater. When we left the house for a month and left the water heater on, our electric bill was nearly $300, and nobody was even home that month.
Yes, thermostatic mixing valves have been around for years. No maintenance required. It basically allows you to heat your water to 150° at the water heater (which is safer as it prevents the growth of Legionnaires and other bacteria but too hot to use at that temperature) and as the 150° water leaves the water heater, the valve adds just enough unheated/cool water from the supply line to balance the temperature to 120°. So one gallon of 150° water results in about 1.25 gallons of water at 120° because you are adding unheated/cool water. Hope that makes sense! The valve I linked to is one that can actually be installed by a skilled DIYer. Any plumber should be familiar with them and be able to provide and install one. Plumbing supply houses carry a variety of them from different manufacturers.

I don't have any experience with heat pump water heaters other than to note that they add significant complexity and lower reliability to an electric water heater.

As far as cost of electricity using a conventional water heater, I have a couple of suggestions. First, install a water heater timer, like the Intermatic EH40 (electronic) or Intermatic WH40 (mechanical). Use it to turn off the water heater after all hot water use is finished for the day (perhaps at bedtime) and turn back on an hour or so before first use the following morning. The tank will keep the water relatively hot so it will come up to temperature very quickly.

Second, when you go out of town, turn off the power supply to the water heater (the Intermatic timers have an on/off button or switch). There is no point in heating water if you aren't there! In fact, it is wise to turn off both the water heater AND the water at the house supply shut-off when you are away for an extended period. That lowers your electric bill and prevents significant damage if a washing machine hose bursts or you have an in-wall water leak while you are away. If you irrigate with water, the supply shut-off for your house should be located downstream from the irrigation system output and shut-off, so turning off the water at the supply shut-off should not prevent the irrigation system from running.

Hope that is helpful!
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by Californiastate »

I'd suggest adding blow down strainers ahead of any proposed TMW.
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

galawdawg wrote: Tue Sep 20, 2022 12:18 pm
SurferLife wrote: Tue Sep 20, 2022 11:47 am
galawdawg wrote: Tue Sep 20, 2022 11:40 am
Bengineer wrote: Tue Sep 20, 2022 6:16 am OP, what does "on its last legs" mean?

We have a thermostatic mixing valve on our tank electric water heater. It mixes the 150d.F. water down to ~120d.F. or so.
As I recommended early in the thread, that seems like a good solution for the OP's situation. Even ignoring recovery, a fifty gallon tank heated to 150° will produce over sixty-two gallons of water at 120° when a thermostatic mixing valve is used with the system.

Using 1.8 gpm shower heads, the maximum flow rate in Hawaii, even if the tank did not heat any additional water when the first shower begins, there would be enough water for thirty-six minutes at 120°. That's certainly sufficient for a family of four.

And since the water heater continues to produce hot water during usage, you get more than that. For example, the least expensive Rheem fifty gal electric at Home Depot will produce sixty-one gallons in the first hour. Heat the water to 150°, add the thermostatic mixing valve, and now you have over seventy-five gallons of 120° water in the first hour or enough for forty-two minutes of showering in the first sixty minutes.
So, I have been looking at the thermostatic mixing valve you linked to, and I'm not quite sure I understand it fully, but sort of understand the concept. Is this a new technology and if not, how long has it been around? Will this be a problem for future plumber maintenance where they have no idea what is attached to the water heater? Does it require any maintenance? Also, is it compatible with the heat pump water heaters or do I need a straight up electric? I do feel that we must go to a heat pump water heater. When we left the house for a month and left the water heater on, our electric bill was nearly $300, and nobody was even home that month.
Yes, thermostatic mixing valves have been around for years. No maintenance required. It basically allows you to heat your water to 150° at the water heater (which is safer as it prevents the growth of Legionnaires and other bacteria but too hot to use at that temperature) and as the 150° water leaves the water heater, the valve adds just enough unheated/cool water from the supply line to balance the temperature to 120°. So one gallon of 150° water results in about 1.25 gallons of water at 120° because you are adding unheated/cool water. Hope that makes sense! The valve I linked to is one that can actually be installed by a skilled DIYer. Any plumber should be familiar with them and be able to provide and install one. Plumbing supply houses carry a variety of them from different manufacturers.

I don't have any experience with heat pump water heaters other than to note that they add significant complexity and lower reliability to an electric water heater.

As far as cost of electricity using a conventional water heater, I have a couple of suggestions. First, install a water heater timer, like the Intermatic EH40 (electronic) or Intermatic WH40 (mechanical). Use it to turn off the water heater after all hot water use is finished for the day (perhaps at bedtime) and turn back on an hour or so before first use the following morning. The tank will keep the water relatively hot so it will come up to temperature very quickly.

Second, when you go out of town, turn off the power supply to the water heater (the Intermatic timers have an on/off button or switch). There is no point in heating water if you aren't there! In fact, it is wise to turn off both the water heater AND the water at the house supply shut-off when you are away for an extended period. That lowers your electric bill and prevents significant damage if a washing machine hose bursts or you have an in-wall water leak while you are away. If you irrigate with water, the supply shut-off for your house should be located downstream from the irrigation system output and shut-off, so turning off the water at the supply shut-off should not prevent the irrigation system from running.

Hope that is helpful!
By default, the common practice of electricians out here is to install a water heater timer, so they already did that without even asking. We tried to use the timer, but were having issues with it, so we're still trying to learn how to best utilize that. It could also be that our water heater just needs to be replaced as it extremely old and I'm amazed it isn't leaking. The heat pump technology offers more programming ability than our timer which just has two on and off settings per day, so if you need more than that it's an issue. I also like that it simply heats more efficiently. I do believe that the thermostatic valve is probably the easiest way forward and will work for us for many years. We are in the middle of determining how to configure the room that the water heater is in, so this might affect what we do later. I guess the bottom line is that it's probably most efficient to put in a 50gal heat pump tank with thermostatic valve and then reevaluate in a few years.

We have started to turn off the water heater and water when we are not at the house for long periods of time and that has reduced our electric bill significantly.
iamblessed
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by iamblessed »

I would buy the 50 gallon or maybe a 40 gallon and teach the family to be frugal. That was what was done in my family and it worked. We had a 30 gallon tank in my family. I still take navy showers to this today. It is a little harder in the winter but no big deal.
ncbill
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by ncbill »

SurferLife wrote: Tue Sep 20, 2022 11:41 am
ncbill wrote: Tue Sep 20, 2022 7:17 am If OP is putting in a solar electric system they've got enough sunshine to put in solar water heating, e.g. a thermo-syphoning system.
We did consider this but decided against it in favor of more PV panels; we have roof space limitations. Also, the cost was around 10k.
Then I would do what galawdawg suggests...crank up the water heater setting to extend 'run-time' at your desired water temperature and add a mixing valve to prevent scalds.

If you have the horizontal space you can always add another water heater...that's what my mom did...two 40-gallon 'short' gas-fired units in the crawl space for 80 gallons total.
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SurferLife
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by SurferLife »

ncbill wrote: Wed Sep 21, 2022 9:09 am
SurferLife wrote: Tue Sep 20, 2022 11:41 am
ncbill wrote: Tue Sep 20, 2022 7:17 am If OP is putting in a solar electric system they've got enough sunshine to put in solar water heating, e.g. a thermo-syphoning system.
We did consider this but decided against it in favor of more PV panels; we have roof space limitations. Also, the cost was around 10k.
Then I would do what galawdawg suggests...crank up the water heater setting to extend 'run-time' at your desired water temperature and add a mixing valve to prevent scalds.

If you have the horizontal space you can always add another water heater...that's what my mom did...two 40-gallon 'short' gas-fired units in the crawl space for 80 gallons total.
This is good information; I never even considered doing two water heaters. It seems like the best way forward is to just put in a 50 gal heat pump water heater with the TMV, and then relook things in 5 years or so. I have space for a second water heater, but I don't know where to put it. I'd consider putting it on the other side of the house which would work great. It seems like doing the tankless is probably not the best way forward, though I'd sure like to get the space back that putting that in would give.
old medic
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by old medic »

Some may call me crazy... Our home built system is a 20 gallon WH.. fed by a small tankless heater. Have a line that comes off before the WH to feed a sink in the utility garage.
clutchied
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Re: Electric Water Heater vs Tankless Electric (space limitations)

Post by clutchied »

so something that can be overlooked is the temp INSIDE your water heater.

50 gal @ higher temps will last longer than 50 gal at lower temps.
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