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By Sherry Listgarten

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About this blog: Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of how our climate is evolving a...  (More)

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Living with a Heat Pump Water Heater

Uploaded: Aug 21, 2022

This is going to be a pretty short blog post because it turns out it’s not all that interesting living with a heat pump water heater. It works, it’s quiet, you pretty much forget about it. When I ask my parents about theirs, it’s clear they haven’t given it any thought at all since it was installed. It just works. But I will cover the sound, the electricity use, and the cost of my installation in some detail for those who are interested.

In May I installed an 80-gallon, 15-amp Ruud heat pump water heater in a closet in my garage, replacing a gas tank water heater that was in there. I got the 15-amp model to save room in the electric panel (vs the more traditional 30-amp model), and I got the large 80-gallon model “just in case”. (That was definitely overkill. A 65 gallon model would have been more than enough for our house.) When first installed it was louder than spec’d, but I reached out to Ruud and the contractor put in some sound-proofing as I described in an earlier blog post.

Since then, I’ve noticed the sound maybe twice, each time when I was in the garage and heard a low hum. I have never noticed it from inside the house. What is the sound like? If I stand in the closet right next to the heat pump water heater, the sound is a low-frequency hum of about 60 dB. Below you can see the sound meter reading, and you can listen to it here. Six feet away, holding the closet door open, the sound is around 54 dB.

If the door to the water heater closet is closed, then the sound in the garage is a quiet low hum, anywhere from 42 to 48 dB depending on where the sound is measured. You can see a meter reading below from about 8 feet from the door, and listen to the sound here and here.

From inside the house, in the family room adjacent to the back wall of the closet, you can just barely hear a hum if you listen very hard. I have never noticed it, and neither has my keen-eared daughter. The sound meter might read 38 instead of 35 when there is no other ambient noise. You can listen to it here, though I couldn’t hear anything when I made that video. But when I listened very carefully as I used the water heater app to turn the heater off, I could hear a slight decrease in sound. (1)

Operationally the water heater doesn’t use much electricity. If you look at the specs for the appliance, it generates 4200 BTU/hour of power when the compressor (heat pump) is running. That is equivalent to 1231 watts (1 watt = 3.41 BTU/hour).

Since the heat pump generates about 3.7 times more power than it takes in, that means it uses about 1231/3.7 = 333 watts. That is about the same as a coffee maker or plasma TV, according to this chart from Silicon Valley Power.

If a house has used a lot of water and the tank is substantially emptied, the resistance element will kick in to quickly fill up the tank. (2) That element uses about seven times as much electricity as the compressor, or 2250 watts, and would use double that if you have a 30-amp model! That is why you don’t want to have a very small tank. With an enormous 80-gallon tank and relatively low household hot water usage, our resistance element has never turned on in the 3+ months the water heater has been running. (3)

In practice, what does this look like? Below is a chart showing a typical day’s power draw (in kW). The pump ran three times for about an hour each at around 400 watts. Most days it runs at around 6am and 9pm because we have a recirc line -- hot water is sent through a recirculating line to minimize wait time for hot water in mornings and at night. It is on a timer and runs from 6-7:30am and from 9-10pm. You can see the heat pump’s compressor operating during that interval. During a busy day with several showers the heat pump water heater might run for 6 hours instead of 3-4.

Below is a chart showing the water heater’s daily energy usage (in kWh) over the last 60 days. (Can you see when my daughter and her long showers came home?)

If you look at the last 12 days, energy use averaged about 1.7 kWh/day. Over the last 60 days, it averaged about 1.4 kWh/day. That is lower than I expected based on my gas water heater use. Last year’s utility bills suggested the gas water heater was using between one-third and one-half of a therm per day. That translates to between 10 and 15 kWh/day. But because the gas heater was only 0.63 efficient, and the hybrid heater is 3.7 efficient, I expected the hybrid heater to use between 1.7 and 2.6 kWh/day (10 * 0.63 / 3.7 and 15 * 0.63 / 3.7). But it’s using less. The weather has been warm, meaning the heater is running even more efficiently than average. I expect that during the winter, daily energy use will get closer to 2.5 kWh, especially when my daughter is home!

The cost to run the water heater for a month, at Palo Alto’s Tier 2 rate of $0.20/kWh, is somewhere between $9/month (if using 1.5 kWh/day) and $15/month (if using 2.5 kWh/day). Our gas water heater, at Palo Alto’s Tier 2 rate of around $2.20, cost between $22/month (if using one-third therm per day) and $33/month (if using one-half therm per day). At the Tier 1 rate of around $1.30, the cost would be between $13 and $20 per month. So the new heater is cheaper to operate, but it’s pretty negligible since we don’t use all that much hot water.

The only downside of this whole project was the installation cost. It cost about $4500 net to install. Materials were about $2500, labor was about $2500, the permit was around $500, extra soundproofing was around $500, and Palo Alto’s rebate was $1500. (4) That cost is okay for some households but absolutely not okay for others. Higher incentives are available in some areas, but costs must go down as more people install these. Sunwork installations are more moderately priced. The new federal incentives will help push the market along as will more aggressive state and local building codes.

Rheem/Ruud has two new “plug-in” models that should cost less to install because they require less electrical work. The HydroBoost seems to be the best fit for our area. It needs only a standard plug, and it uses higher water temperatures and a mixing valve to increase the effective capacity of the tank so that it is less likely to run out of water. The tank has no resistance element, so it refills at a rate of only about 12 gallons per hour. The other model they offer has an extra-large heat pump that fills the tank at a rapid 28 gallons per hour. However, it requires a dedicated circuit and I worry that the powerful compressor will be loud, though I haven’t heard any reports. If you are interested in that model, I would ask about the sound. AO Smith also has a new 120-volt plug-in model that is worth looking at.

Anyway, my heat pump water heater has been a non-event since it was installed. We don’t notice it, it works great, and the utility bills are slightly lower. I think in five years we are going to think it strange that anyone would bother to read a blog post about these appliances. They will just be standard and no one will care much about them. Palo Alto has already taken some steps in that direction by requiring remodels and additions to use them. It makes sense to avoid installing new long-lasting gas appliances when practical, as it is in these cases. With gas water heaters contributing about one-third of our household gas use in this area, switching to the heat pump water heaters can make a big dent in building emissions.

I’d love to hear your experience if you have installed one, or any questions you may have if you are considering one.

Notes and References
1. The wall between the closet and the family room is insulated and also has QuietRock on the garage side, glued with some sound-proofing glue. I’m not sure how much of a difference that made.

2. I am operating the water heater in the recommended “Energy Saver” mode. The “High Demand” mode will cause the resistance element to kick in more aggressively, for example if you have house guests and need to accommodate an unusual number of showers or other hot-water loads.

3. I know this because I have an Eyedro circuit monitor on the water heater circuit, so I can see how much electricity it is using and when. I recommend installing one of these if you get a heat pump appliance, since it can help you to understand your usage and ultimately your electricity bill.

4. These costs are approximate because the electrical work was combined with other things, as was the permit. The cost is also on the high side because the contractor did a bunch of drywall work in the garage in addition to installing the heat pump water heater.

Current Climate Data (July 2022)
Global impacts, US impacts, CO2 metric, Climate dashboard

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Posted by CyberVoter, a resident of Atherton: other,
on Aug 21, 2022 at 7:48 am

CyberVoter is a registered user.

Blogger's note: I have removed a comment from CyberVoter in Atherton because it contains several unsubstantiated and incorrect claims. CyberVoter, please feel free to republish with links. For example, you say that most people are paying more than $.45/kWh for electricity. Where do you get that information? You say that there are a number of things that would make a bigger difference than decarbonizing buildings, like stopping High Speed Rail. What are the projected net emissions from High Speed Rail, and how does that compare with building emissions, or even just residential water heater emissions? You say that a dog is as polluting as an SUV. Again, data?

I hear your frustration about electrification and your concern about the growing demand. But I ask that assertions made in comments on this blog be grounded in facts and not in fears.

Posted by Matt Schlegel , a resident of Duveneck/St. Francis,
on Aug 21, 2022 at 7:56 am

Matt Schlegel is a registered user.

Great article. I'd like to add one additional point. The heat pump water heater (HPWH) takes heat out of the air and puts it into the water in the tank. The exhaust is cool air. In other words, the HPWH is also an air conditioner! Our HPWH has kept our garage cool all summer, and by not having a hot garage attached to the house, the house has stayed very cool as well. We installed a home air conditioner several years ago and we have yet to turn it on this summer. Our efficient HPWH is giving us the double benefit of hot water and a cool house.

Posted by caseyc, a resident of Downtown North,
on Aug 21, 2022 at 9:26 am

caseyc is a registered user.

That air conditioning benefit of a heat pump is a real bonus, who knew?! I really appreciate all this information re installation and features because I'm sold on heat pumps, and we will replace our old gassy heater with one as soon as it's feasible.

Posted by Ronen, a resident of Menlo Park: Suburban Park/Lorelei Manor/Flood Park Triangle,
on Aug 21, 2022 at 9:49 am

Ronen is a registered user.

Thanks for this post.

The next decarbonization project for our household is the water heater.
The one after that is the furnace.

Gotta get rid of that carbon!

Posted by eileen , a resident of another community,
on Aug 21, 2022 at 1:39 pm

eileen is a registered user.

I am the parent who hasn't given a second thought to our 65 gallon 30 amp HPWH installed in September 2021. It provides plenty of hot water when we need it. Rebates from BayRen and Peninsula Clean Energy totaled $2650 bringing the net cost to $4300. We haven't noticed a big impact on our electric bills, but maybe we ignore those too. Now that we have also installed a heat pump for space heating and gone fully electric, we have qualified for an increased tier 1 allowance from PG&E, so maybe I will start paying attention to those electric bills. Now that our 125 amp electric panel is maxed out, consideration of the 15 amp model HPWH might have been a good idea.

Posted by Sam Li, a resident of Walnut Hills,
on Aug 21, 2022 at 10:42 pm

Sam Li is a registered user.

PG&E rates are significantly higher than City of Palo Alto electric rates, greatly extending the "payback period."

Glad to hear the 15A plug-in version is now available.

If your electricity is generated by burning gas your carbon reduction is not 100%. Much of the US electric supply comes from this source.

Sunwork is truly a gem.

Thanks for your article, I hope you continue enjoying your hpwh for many years to come.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 22, 2022 at 4:43 pm

Sherry Listgarten is a registered user.

Thanks for the great comments/questions. I also got a few in email, so I will address those here as well.

Someone emailed me asking about whether a closet installation works. Yes, if well vented, per the installation instructions. It is also the case that you can get a HPWH with a duct kit, and in my case we ducted the output air into an adjacent large closet that has a refrigerator in it, figuring the cold air would help the refrigerator run more efficiently while also removing it from the intake. The HPWH closet gets air from outside (there is a vent) as well as from the garage. The large closet next door has two doors, both of which vent to the garage via gaps underneath the doors (cold air sinks). I will try to do a follow-up in the spring that covers efficiency of the appliance in winter.

The closet installation shown below has a duct on the inlet, so that air from the adjacent garage enters the water heater. There is no duct on the outlet (the venting on the right of the tank), which is oriented towards some vents on an exterior wall. A tricky part about closet installations is getting the tank oriented properly so that the ducting and piping and condensation line all fit nicely and the keypad is easily accessible.

Someone else emailed me this link with information about credits and rebates via the Inflation Reduction Act, pointing out that credits are available to all (not income-qualified), though they are capped at $2000 annually and may need to roll over if larger. This reader is excited to take advantage of Sunwork’s lower cost installation, a BayRen rebate, operational savings, and the tax credit. He lives in a condominium in Santa Clara and is sharing the information with his neighbors who want to reduce their gas use but may not understand their options.

@Matt mentions the nice cooling effect in summer and a reader in email mentioned the dehumidifying effect, which can be nice in a basement. I did hear a homeowner say that in the winter it is less comfortable for him to do wood-working in the garage when his HPWH is running, though it is more comfortable in the summer.

@Sam, I agree that with PG&E rates there isn’t much in the way of operational savings. So the rebates and tax credits will have to be enough. On the other hand, I just learned that Santa Clara has electricity rates of $0.12/kWh (!!). I would really like to see electric rates come down relative to gas in more places. Re the electricity supply, California’s was 52% emission-free in 2021 (renewable and nuclear and large hydro). The US was 39% emission-free. Those numbers are not bad, and getting better every year. Finally, yes, I agree that SunWork is a great organization. There are lots of opportunities to volunteer with them if people are interested.

Thanks again for reading, and for the really informed and interesting comments.

Posted by Local Resident, a resident of Community Center,
on Aug 23, 2022 at 8:26 am

Local Resident is a registered user.

Many houses in Palo Alto have detached garages or their garages have been converted to living space. For these older homes the water heater is often in the living space, sometimes in a closet. They do not come close to meeting the space requirements for a heatpump. These houses are not well suited to install a heat pump water heater. Also, the noise is much more impactful. Lastly, heat pump water heaters can be much more costly to install. I strongly support subsidies and even increasing the subsidy. However, I think its too soon to mandate that any house be required to only replace their water heater with a heat pump water heater.

Posted by Bob+Dylan, a resident of Crescent Park,
on Aug 23, 2022 at 9:02 am

Bob+Dylan is a registered user.

Sherry - such an interesting (& detailed) article. Thank you. I have an older home with a basement, which is where my hot water heater is now. I gather from your comment to Matt that a basement location is doable? So interesting about the cooling effect.
Thanks again.

Posted by Dean Samos, a resident of Los Altos,
on Aug 23, 2022 at 10:30 am

Dean Samos is a registered user.

I love my HPWH. We installed ours back in May 2021, and I can see my gas usage during the summer months dropped from 13-15 therms/month to 2-3 therms/month. That's what we use for cooking. The sound is not an issue - we also have a recirculating pump that turns on 2-3 times/day just like you Sherry. I hear a sound kind of like wind blowing when the heater is operating. The fact that it cools our garage while heating water is a bonus too. We paid $1700 for our heater from Home Depot, paid $1000 for installation and miscellaneous parts (I helped the installer a bit), $83 for the permit in Los Altos, so after our $2000 rebate from SVCE, ours only cost about $800 net! I'm looking forward to getting a heat pump home heating system to replace our gas water heater in the future.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 23, 2022 at 10:32 am

Sherry Listgarten is a registered user.

@Bob: Yes, it is very common to put a HPWH in a basement.

@Dean: Fantastic! I hope pricing like that becomes the norm soon.

@Local: I agree that not every existing single-family home has an easy path to a HPWH right now, though I think most do. (Homes with tankless water heaters might be one example.) I would love if the city would pick 100 homes at random and analyze what it would take to install a HPWH so they can get a better idea of what the gaps are that need to be addressed and where they might mandate electric replacements with little downside. Ideally they'd already have that info from the Home Genie program, though I don't believe they did that analysis early on. (Not sure they do it now, for that matter.) For now, imo incentives for residents and contractors are the way to go for existing homes while we build the workforce and evolve the tech, and fortunately we now have help from the federal government in that vein!

Posted by Mondoman, a resident of Green Acres,
on Aug 23, 2022 at 10:55 am

Mondoman is a registered user.

"I would love if the city would pick 100 homes at random and analyze what it would take to install a HPWH so they can get a better idea of what the gaps are that need to be addressed and where they might mandate electric replacements with little downside."

Yes, exactly, and publish their findings perhaps in scenario or case study form so we can all have realistic information on what replacement might involve in our homes. Before your excellent blog posts, I would not have thought of space/clearance and electrical circuit issues in the context of a water heater.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 23, 2022 at 11:06 am

Sherry Listgarten is a registered user.

@Mondoman: Fortunately, the industry has known about those limitations for a long time, which is why Rheem has the new Hydroboost model. It can use a standard plug -- no electrical work needed -- and it can go in any size room or closet as long as the inlet or outlet is ducted. (The latter is true for traditional models as well.) It's not quite as efficient as the traditional HPWH model since it heats water to a higher temperature. And it doesn't work in all climates. But it is a great option for our area imo.

Posted by Duveneck neighbor, a resident of Duveneck/St. Francis,
on Aug 23, 2022 at 2:53 pm

Duveneck neighbor is a registered user.

Why do you assume CPAU Tier 2 rates of $0.20/kWh? Tier 1 rates are $0.144/kWh. Even when our children lived at home, we paid only Tier 1 rates.

Posted by Markie, a resident of Palo Verde,
on Aug 23, 2022 at 5:39 pm

Markie is a registered user.

Please speak up if you have information on a "combi" solution for Eichler homes that have both a standard gas water heater and a gas boiler to heat the water circulating through the radiant floors.

Such a combined unit would be the last step needed to eliminate all natural gas appliances.

And also another vote for induction cooktops - they rule!

Posted by Nan Olson, a resident of Midtown,
on Aug 23, 2022 at 9:19 pm

Nan Olson is a registered user.

Our gas waterheater is in a corner of the laundry room, not in a closet. Any problems with replacing it with a heatpump?

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 24, 2022 at 11:29 am

Sherry Listgarten is a registered user.

More great questions! My 2c:

@Duveneck: Yeah, good question. It's partly because I want to err on the conservative side, and don't know how many people are in Tier 2. But it's also partly because as we electrify transportation and buildings, I expect that almost all of us will be in Tier 2 unless Palo Alto increases the size of Tier 1 (as PG&E has done) or provides a separate rate for EVs, or ...

@Markie: Both Chiltrix and Harvest Thermal will heat both radiant (or fan coils) and hot water. Only Chiltrix will cool radiant as well. I get asked this question a lot. These combi systems are apparently pretty common in Europe.

@Nan: The main downside I can think of is that in winter your heating bill would go up as the heat pump water heater works hard to cool that part of the house. It could also get uncomfortably cool for doing laundry. You might want to consider ducting the outlet to the outdoors if there is a convenient exterior wall and/or closing the door to the laundry room in the winter.

Posted by David Fradin, a resident of another community,
on Aug 24, 2022 at 11:51 am

David Fradin is a registered user.

The local Rheem salesperson says that the dedicated and/or shared 15A Pro can only be purchased by a licensed contractor. The distributor is Pace. Pace says they expect to have hundreds in stock in late Sept or early Oct 2022. The list price for the 50-gallon model is about $4000.

I have not had much luck finding a contractor that will do the installation. Got just have one quote so far at $12K which makes it a no go.

I suspect a better quote would be for 8 hours of work at $150/hour for a labor of $1200 plus, say $3000 for a total of just over $4000. I have a rebate reserved from SVGE, plus the new IRA credit should make the installation a no-brainer. My gas bill to heat hot water runs about $60/month for two people in Los Gatos

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 24, 2022 at 7:27 pm

Sherry Listgarten is a registered user.

@David, for installers, you might ask Pace who is in there a lot picking up HPWH's. Or look at Silicon Valley Clean Energy's list or Palo Alto's. Peninsula Clean Energy also has a list here, though it hasn't been updated in a while.

Posted by Mark Lawrence, a resident of Midtown,
on Aug 24, 2022 at 10:55 pm

Mark Lawrence is a registered user.

Very informative article, it allayed many of my concerns about HPWH; in particular, no one reports running out of hot water.

However, there is a bit of confusion about units. You said " it generates 4200 BTU of energy ... equivalent to 1231 watts (at 3.41 BTU/watt)." But a BTU is a unit of ENERGY, and a watt is a unit of POWER (rate of energy use.) A Watt (1 Joule per second) is equivalent to 3.41 BTU PER HOUR.

4200 BTU PER HOUR would equate to 1231 Watts.

I think one reason people get confused is because the Watt is a rate unit (1 Joule per second) but doesn't sound like it, and we use bastard units like "watt-hour" which is "joules per second hours", kind of like measuring distance in "miles per hour days".

I'm taking a more serious look at HPWH now, mine would be powered by my surplus solar electricity. gotta figure out if my electric panel can handle it.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 25, 2022 at 7:25 am

Sherry Listgarten is a registered user.

@Mark, thanks for reading so carefully and for pointing out the units problem. Apologies for the oversight, and it's been fixed!

Posted by Proud Taxpayer , a resident of Willowgate,
on Aug 25, 2022 at 12:26 pm

Proud Taxpayer is a registered user.

Great column. And great timing. We are thinking about getting a HPWH this year. We just put more solar panels on the roof. Who would we reach out to first to see how feasible a HPWH is for our situation?
We do have some interesting complications.
* existing GWH is in an interior closet, not next to an exterior wall.
** it is plumbed for water, of course
** it is vented up for exhaust for the gas fumes
** the door has vents at the top and bottom.
** it has no electricity and no floor drain
Don't know if any of these will prove to be showstoppers.

Posted by Dr. Strange, a resident of Blossom Valley,
on Aug 25, 2022 at 12:41 pm

Dr. Strange is a registered user.

I think it's been mentioned, but I am jealous of your Palo Alto electric rates! Based on your numbers (thanks for the analysis!), a heat pump water heater would probably cost us nearly double in energy costs compared to our tankless gas heater. This makes me wonder if converting to a heat pump for winter house heating would also end up costing us more -- I'm guessing it would. :-(

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 25, 2022 at 4:15 pm

Sherry Listgarten is a registered user.

@Proud, you might want to talk with and get estimates from a few installers. You can look at Silicon Valley Clean Energy's project list or Palo Alto's contractor list. Peninsula Clean Energy also has a project list, though it hasn't been updated in a while.

I expect the question will not be whether it can be done but at what cost.

@DrStrange: Not sure how you get to double the cost. If your tankless heater is a maximum 100% efficient, then the HPWH is "only" 3.7x more efficient, which translates to $2.38/therm if your electricity costs $0.30 (1 therm = 29.3 kWh). That is ballpark what PG&E charges for gas, definitely not 2x.

Interesting question about a winter house or even a summer house. I agree that a house with frequent short stays, where the tank is cooling between visits, seems to be a better fit for a tankless heater.

Posted by Eddie, a resident of Fairmeadow,
on Aug 27, 2022 at 3:14 pm

Eddie is a registered user.

For those who don't have the space, what's your opinion on electric tankless water heaters?
We did a full house remodel in 2017. Our house is much greener in terms of electricity, gas and water usage - but it is not perfect. We replaced our old gas tank water heater with gas tankless water heater, partly to save space. We have absolutely no room for an HPWH (the architectural plans were designed around the smaller footprint of a tankless heater).
During the remodel, we lived in a Palo Alto townhouse that had a tankless heater in the garage. There was no room for the tank.
Many houses will never have the room for an HPWH, unless they go through major renovation (which in itself has a tremendous carbon impact). So IMHO electric tankless water heaters should be discussed as options for such houses.

Stepping back, I've listened to many seminars and read many articles about trying to reduce ones carbon footprint. They all say to install an HPWH, an inductive stove, buy an electric car, ...
I think that's the wrong approach.
The emphasis should be (1) try to switch from gas to electric and try to make the electric usage (2) more efficient and (3) more clean. How you go about 1-3 above is different for every person (depends on needs and finances) and every house. I have yet to see seminar, article, ... that says, "This is what you should do if you can't fit an HPWW in your house."


Posted by Sherry Listgarten, a Mountain View Online blogger,
on Aug 27, 2022 at 4:25 pm

Sherry Listgarten is a registered user.

@Eddie, those are Such. Good. Questions. I completely agree that the “right” order is different for different people. I think the “right” order reflects what’s easiest for people, what appeals to people, and what makes the biggest difference. In our house we started with cutting out red meat, since we weren’t particularly attached to it, it was good for the environment in many ways, and it was good for our health and wallet. But another family might want air conditioning, so they might start by replacing a furnace with a heat pump, or even just adding a heat pump and using it for heating as well, preempting their gas furnace. For someone else, halving their overseas trips might be a big win and not very hard, plus it would save them money. Or commuting via e-bike instead of a gas car. Or getting an EV. Or even just adjusting their pool pump to run midday instead of in the evening. My advice is always to find somewhere easy/appealing (for you) to start, spend time getting that under your belt, getting it to stick, and celebrating your emissions win. Then pick something else, and keep going. The order doesn’t matter so much as the momentum and finding things that work.

So, to begin with, I’d say if it’s a huge pain to replace a tankless water heater, fine, don’t worry about it. There are plenty of other ways to reduce emissions. There are good calculators at and Or, if you particularly want to do something about your water heating emissions, consider using less hot water. What is the temperature on the heater? How long are the showers? Can you do more laundry in cold water? Can you adjust your recirc timers? This is all more fun, though, if you can see the impact, and that is hard to do with a single gas appliance. It’d be great if someone built an easy-to-install single-appliance meter for this kind of thing

If after all that you really feel like you should replace your tankless gas water heater, and you have absolutely no room for even a 40-gallon tank (plus mixing valve), then your options are not great. The tankless electric water heaters can use huge amounts of electricity -- they often take up 100 amps or even more in your panel -- and are probably best only when very little hot water is used. (In which case, why is this a priority?) The other option is to build an exterior closet onto your house for a tank water heater. Solar hot water might be an option, but the installations I’ve seen also need a tank.

So, that’s how I would think about it. One good thing about the fact that we all have such big carbon footprints is that there are many ways to cut back. If you find something that is really hard, my advice would be to not worry about it, move on. But be honest with yourself, find things that stick, and prefer bigger things to smaller things.

That’s my philosophy anyway. Maybe others want to chime in as well. I hope this is a little bit helpful…

Posted by Sam Li, a resident of Walnut Hills,
on Aug 30, 2022 at 3:48 am

Sam Li is a registered user.

Thinking a bit outside the box (perhaps outside the borders) it's shocking how much energy the US wastes keeping water hot "in case" someone may want it.

There are so many countries with point of use water heaters at kitchen sinks
and power showers (UK term) in the bath.

We should do an analysis of the cost of those appliances vs the endless cost of keeping a large quantity of water hot 24 x 7, "just in case" someone may use it.

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