Heat Pump Hot Water Heater in Our Region

Submitted by MrTipps t3_125rbjl in philadelphia

Old gas hot water heater is ready to be replaced. There's a big push for installing new hybrid heat pump hot water heaters (better efficiency, refunds/tax credits, environmental benefits, etc.), but some neighbors are saying that they underperform in our area (water gets too cold in winter, water heater struggles to keep up). Not sure if they just have old/crappy models, didn't use them correctly, or if they legitimately just aren't effective with our winter weather.

I know how they work--just trying to evaluate how *well* they work. Has anyone here had one installed in the last year or two and have results--good or bad--to share?

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Brraaap t1_je5gnem wrote

Heat pump water heaters are slow, if you buy one with the same size tank as you're replacing you will be disappointed. Also, there have been improvements recently, mainly they hold the water at a higher temperature now and mix it with cold to reach the desired temperature and make the tank last longer

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calvinistgrindcore t1_je5gv8m wrote

I haven't installed one but am about to take the plunge due to the tax credits available this year. So I've done a deep dive into the pros and cons. When you say "hybrid," are you referring to a single outdoor heat pump that heats the home AND the water? It's worth distinguishing, because yeah -- in general, air source heat pumps become marginally less efficient as the outside temperature drops. Just as in deep cold it might take said heat pump longer to raise your indoor temp by X degrees, it also takes longer to raise the temp of a tank full of water. When I see complaints online about heat pump water heaters, it causes me to wonder if people undersized the tank -- like, did they get a 50 gallon when their use patterns would've been better served by a 100 gallon?

I have an air source heat pump already that heats and cools my house. We also have an older gas boiler that does radiator heat as a backup. This winter, we used the boiler/radiators on exactly 20 days total. The heat pump covered the rest of the winter, no problem. But interestingly, I found that I saved money on the heat pump by eliminating programmed nighttime setbacks on my thermostat -- the heat pump worked more efficiently by maintaining temps over time than by having to raise them quickly in the morning, at the coldest part of the day. That kind of "high inertia" performance (for lack of a better term, I'm not a scientist) would indicate that maybe sizing up to a larger tank would be a good idea for a water heater.

I'm now looking at getting a *separate* heat pump water heater to put in my basement. The cool thing about these is that they are effectively air-conditioning your basement in order to heat your hot water -- they just move heat from the surrounding environment into the water in the tank. So in this region, I think there are some extra benefits in that a basement HPWH can dehumidify your basement and effectively suck up waste heat from boilers, hot water pipes, dehumidifiers, dryers, etc. But it does make the basement itself colder in those winter months.

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DrSilverthorn t1_je5gywk wrote

I looked at it and decided to go conventional. But my reasons were additional noise and complexity.

If the HWH is in a heated space, then it should be fine. If it's not, then heating the water with the built-in heat pump would not be effective in very cold weather.

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Buck3thead t1_je5i8wk wrote

Where will your water heater be installed? In a basement, with no access to outside air?

I don't have one installed but needed a new water heater a few years ago and considered getting a heat pump model. I decided against it, and in favor of an electric Rheem Marathon, for a couple of reasons:

  1. Heat pump water heaters are more mechanically complex than traditional electric, with more opportunities for failure. This was the main reason.

  2. A heat pump water heater extracts energy from the ambient air and uses it to heat your water. If you're in a Philly rowhouse and your water heater is in the basement, the heat pump is going to be less efficient than it could be because it's extracting energy from your basement air, which is:

  • Heated by your home heating system, which will have to work harder to make up for the lost heat.

  • Limited in energy capacity because there isn't much air volume in your basement and it doesn't move around much.

So it's not as efficient as, for example, a mini-split heat pump you'd use to heat your house, where part of the system is outside the house and it can pull energy from the outside air, which is a "free" source of energy and also there's way more of it available.

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porkchameleon t1_je5idvq wrote

OP, why do you have a hot water heater? If the water is hot, why do you need to keep heating it up?

I suggest you look into cold water heaters, you could be being scammed with that hot water heater jawn.

EDIT: or is that "hot water heater" is the same as "naan bread" and "chai tea" around here?

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MrTipps OP t1_je5j1kn wrote

Replying to calvinistgrindcore (#2,450,664)

No, just using the "hybrid" term in the way that most manufactures use it: the water heater uses a heat pump and an electric element, but can run from one or the other or both. Not talking about single outdoor units or split heat pump water heaters that put the heat pump outdoors. Air source heat pump for cooling/heating (with supplemental heat from the existing gas boiler & radiators) is a future project.

Sounds like you're considering putting in the same thing that I'm considering and for mostly the same reasons. Are you sizing up to a larger capacity unit than your current water heater?

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mistersausage t1_je5lkgy wrote

It will be fine. At worst it runs the resistive heating coils like a normal electric water heater.

Electric resistance heat is slower to heat than gas, so if you take long showers or do shitloads of laundry, buy a bigger tank than you have now.

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pcurc t1_je5tcvp wrote

Replying to mistersausage (#2,451,548)

I actually have one and can echo that it will be fine. Replaced a gas water heater with a Rheem ProTerra model a little over a year ago, installed in our basement by Gen3 Electric. In everyday use (household of 5), the only times we might run short on hot water is if kids take baths back-to-back, and even then it doesn’t take terribly long to recover.

A side benefit is that it will cool and dehumidify your basement in the summer as long as there’s enough air flow in and out of the space where the unit is installed.

The only caveat is that Rheem had an issue with some units that caused it to make an ungodly loud hum when running the heat pump. The solution was a new fan which they provided and Gen3 installed for free, though it does require taking the top casing off the water heater so adequate space above it helps a lot - but I think by this point this problem has likely been resolved in more recent production runs.

Happy to answer any other questions you might have!

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all4whatnot t1_je5ywvk wrote

I had one in an apartment I rented years ago in Media. It worked great and my utility bills were low. It had an "e-heat" setting for when it got too cold out - I believe the description was that the heat pump couldn't quite keep up in very cold temperatures. But I've read that even this isn't a challenge for new heat pumps.

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calvinistgrindcore t1_je5z9mn wrote

Replying to MrTipps (#2,451,081)

>Are you sizing up to a larger capacity unit than your current water heater?

No, but in my case that's just because the one we have is too large for our needs anyway. I'll stay at the same size for the new one. It does seem like for most people, sizing up is the way to go.

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flaaaacid t1_je6g59n wrote

They do perfectly fine in this region. I installed one at my mountain cabin where it's colder than here and it works great. It sits in a mostly-unheated basement so I think I'll be seeing much greater savings in the summer when it's all a bit warmer down there. But for my scenario I was replacing a resistive electric heater and literally any savings is better than what I had.

Even with it being around 50 degrees in the basement it runs in heat-pump mode most of the time, though the resistive coils definitely kick in.

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thecw t1_je6va5i wrote

I mean, there is a known floor on how cold the water can get.

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rane56 t1_je77g0s wrote

So you really should talk to a plumber or energy expert, I don't think many people here have an idea how these things work.
You seem to though, the heat pump part will attempt to pull enough heat out of the basement to produce your hot water but it won't cause its cold here so the electric elements will do a bulk of the work. You will basically have an electric water heater, look at first hour recovery rates if concerned about capacity. Between you and me, stick with the gas fired chimney vented heater, gas always flows even when the power goes out.

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VeryStab1eGenius t1_je7cyzl wrote

I’ve just signed a contract to have one installed and you will not believe the pushback I hit from several of the bigger name plumbers. One company wouldn’t even take the job and two wanted to charge over $2k for labor. I ended up going with an independent plumber.

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MrTipps OP t1_je7eut0 wrote

Replying to pcurc (#2,453,130)

Did you upsize for the heat pump model or go with the same size that you had previously? This wasn't the coldest winter that we've had by any stretch, but I'm assuming you didn't have any issues this winter? Nothing that got you thinking "I've made a huge mistake"?

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pcurc t1_je7j90w wrote

Replying to MrTipps (#2,465,196)

I think I went up by like 10 gallons, nothing major. The only thing that made me think I made a mistake was the humming, but once that was fixed it’s been smooth sailing. Obviously it uses less power in the summer but hot water availability was not perceptibly impacted by the winter weather.

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HonnyBrown t1_jedl8nm wrote

Go through the electric company for rebates

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