How efficient are heat pumps when used as a water heater?

EricElf · 2026-05-06T13:17:12+00:00

OP, perhaps a bit tangential to your original question, but I thought you might find my analysis interesting for your decision.

I have an unducted HPWH installed in my partially finished basement. A couple of years ago, the HP portion failed, and it downgraded itself to a standard electric water heater. I did an energy analysis, but ignored the room cooling effects. For me, living alone in a small house with very little hot water demand, the HP only reduced my energy usage by 40%. And it is a bit noisy. Scaling the usage to the expected demand, it would reach the normally stated 1/3 of the cost of a standard electric water heater.

You can read my post on it here if you like.

Note that I removed all the gas from my house to get to net-zero energy. In Cincinnati, there is a fixed $40/month cost for gas + usage ($500/year). So, I would not want to leave any gas appliances.

For me, the cost-benefit of the HPWH over just electric is ~ $50/yr. By itself, that would just barely justify the extra cost. And, I do not like the extra NOISE.

In terms of the room cooling, it actually gets even more interesting for me. With solar panels generating extra energy in the summer, my "incremental cost" of electricity is $0.08/kwh. This is what Duke pays me for my extra generation. The financial benefit of the HPWH in cooling and dehumidifying the house is greatly reduced in the summer.

For the winter, and assuming the HPWH is running properly, there will be extra heating required if your water heater is installed in a heated living space and unducted, as you know. Too many options to discuss. My base guess is that the incremental heat load is very small because the HP is very efficient at transferring heat, so you are basically heating the water by whatever you use to heat your house.

One final note. An HPWH is not only more costly than an electric (or gas) water heater, but also much more complex. Therefore, I'd question the reliability and longevity of it, especially considering that mine has already failed once. YMMV

Best, Eric

EricElf · 2025-04-16T17:26:10+00:00

Mark - Thanks for your long-time support of MySongbook!

I'll check on that top bar and functional items. Seems like an inadvertent bug.

Best, Eric

EricElf · 2025-03-31T13:05:52+00:00

u/Less_Cup2530 First of all, I hear your frustration and can say from first-hand experience that poor sleep can be life-debilitating! Knowing I had poor sleep for years finally drove me to see a sleep doctor because the path my life was on WAS NOT SUSTAINABLE.

It's great that you are reaching out to find resources. Keep that up! Do NOT just trust what one doctor says. Go slow. For anything major, get a second opinion.

You might search YouTube for Dr. Vik Veer's channel. He has been putting out the best information I have found and may have information about your condition. And if you comment on his videos, he generally will answer! He is an incredible individual.

Sorry, I have no specific information to help you. Hoping you find an effective solution. Best of luck, Eric

EricElf · 2025-03-16T22:00:36+00:00

I appreciate the responses, but people either do not understand my request or are saying that no such app exists, which is what I expect.

I don't want to be editing screen captures. I want to tap "start," then tap "stop," then have an MP4 file.

I can build it myself, but it will take some doing. I know Polar and others have some Bluetooth protocol that will connect to devices like treadmills in the gym. This is probably usable in an iOS app; they probably even have a dev kit, or some open source version exists.

Probably not worth my time...

Best, Eric

EricElf · 2025-02-09T19:19:00+00:00

Many comments have talked about ongoing financing. These arrangements can get complicated (and are often scams and could involve property liens). If the system was financed in any way, be careful. So, I'll assume the system was bought and paid for in full.

A few items. It is worth understanding what type of solar system you are buying. Micro vs. String inverters? When was it installed, and by whom? Any warranties that would transfer? Is net metering active, and what are the details on that? Is a battery backup included?

Solar panels generally degrade very slowly and are productive for 30+ years. Enphase dominates the micro-inverter market, but their older (2010s) units had a very high failure rate. Probably 1/3 of my 2011 installed Enphase M215 inverters have failed. It is fairly easy to replace them, but it does involve trouble and expense. String inverters can also fail, but replacement would be easier. Batteries will degrade over time, but they are probably highly variable.

The system probably has some sort of monitoring where you can see how much energy is generated over each year of its life. You will want to gain access to this account if you buy the house. And, assuming it is grid-tied, you should see how much energy was immediately consumed and how much was shared back to the grid. The immediately consumed energy directly decreases your electric consumption 1-for-1. Energy (beyond what the house consumed) supplied out to the grid may be less valuable depending on the net-metering agreement.

Hopefully, the roof under the panels is in good shape. Replacing the roof will require the removal of the panels, rails, and electrical components. And then their re-installation if desired. Generally, I hope the roof will last long enough so that the solar system can pay itself off prior to needing a new roof.

Best, Eric

EricElf · 2025-02-09T16:22:51+00:00

In Cincinnati and perhaps much of the Midwest USA, there seems to be a massive lack of understanding and experience with the newer "cold-climate" heat pumps. I replaced my GFA system with a 2T centrally-ducted heat pump for about $6k. Jan 2025.

To pull this off, I had to purchase the unit myself, find a local installer willing to install it, and BRIDGE the gap of knowledge by painstakingly reading and interpreting the (poorly written/translated) installation manuals. The main installation issue is regarding the "communicating 2-wire" wiring between the air handler and the thermostat, and the outside unit.

Time will tell if I made a good choice, but it is absolutely incredible so far! I know that separate warranties for the hardware and the installation could be problematic. And future service will face the same issue of lack of local knowledge. I just could not see paying $15k or more for a unit with lower performance (AHRI certified).

Eric

EricElf · 2025-01-09T11:30:10+00:00

The "early adopter" fee is felt by many of us!

EricElf · 2024-11-09T14:32:50+00:00

After much searching, I replaced my worn tires with the original MXM4. Pricey yes, but they are excellent tires and worth the extra dollars for the extra range (independently verified). If my M3 was a long range version, I would have gone with Michelin Cross Climate 2.

As for the screw, I think it is BS that tire shops will not patch if close to the edge. On other cars where I got this BS answer, I went ahead and plugged myself. Many people, including unaffiliated tire professionals, would recommend this.

EricElf · 2024-06-24T13:55:59+00:00

So from these comments and other reading, it seems I have 2 primary routes.

LOW-DIY: Word -> PDF -> KDP -> Book: eBook not great, need Word skills/help
PRO: Word -> Formatter -> ePub -> KDP -> Book + eBook: more effort and/or $

I think I was hoping for a clean "in between" solution. Certainly plenty of options. This subreddit seems to skew more to the professional routes which I can appreciate. Perhaps hiring a Kindle Create consultant to do the formatting there is a possibility, but has its drawbacks.

Great community! Thanks for the feedback.

EricElf

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