Heat pump water heaters

Personal Finances Building / Maintaining a Home
1

As if a new washing machine wasn’t enough …

I just learned that our state is heavily incentivizing the replacement of gas water heaters with electric, heat pump water heaters. I didn’t even know that was a thing until now. Of course I’d heard of heat pumps, for cooling and heating a home, but water? Sure enough, they are real.

Not only are they real, but they are really efficient compared to ordinary electric water heaters, or even our gas unit. So there’s a lot to like about them, and it’s easy to find their advantages.

Our current gas water heater is 21 years old. We flush it every year or two, so it might continue working fine for many more years, or it might go out unexpectedly any day. I figure if we can get reimbursed for most or all of a new, more energy efficient (and cheaper to run) heat pump water heater, why the heck not?

But are there disadvantages? These are all I’ve come across so far. If I’m missing something, I’d really like to know about it, since I’m not confident a contractor will point it out.

o They’re noisy (not an issue, as it’d be in the garage).
o They require additional maintenance, besides an annual flushing (didn’t sound like it was much).
o Requires adding a dedicated 220V, 30A circuit (also subsidized, to some extent).
o Requires creating a way to remove condensate.

Before getting quotes to see just how much it would actually cost us out-of-pocket, I wanted to make sure I wasn’t missing something that would nix the whole deal. Anyone have one of these, and like or hate it?

Ken

2

You would need the new circuit even if going to a non-heatpump electric heater, so that’s kinda a wash.

Upside - they cool the garage slightly in the summer.

They’re somewhat smaller capacity than the old-style electric that’s the same size.

We have one, works fine.

2 Likes
3

But are there disadvantages? These are all I’ve come across so far. If I’m missing something, I’d really like to know about it, since I’m not confident a contractor will point it out.

What will be the BTUs delivered to the water for the different types?
ie. How fast will the water heater recover after using water out of it?
What’s the capacity (tank size)?
If the tank is big enough, and your needs are small enough, recovery speed may not matter.

Another disadvantage is that it’s a much more complex thing. I would not expect it to last 21 years. Your gas fired heater is likely really simple - basically no moving parts, just a sensor to tell it when to turn on/off, a valve, an ignitor, and the flame manifold. A heat pump has a compressor, an expansion valve, and all the pipes with refrigerant in them.

3rd thing I’d look at is cost per BTU delivered.
Natural gas is not as efficient as a heat pump.
But it is usually a lot cheaper than electricity - often cheaper to use gas to provide heat.
Gas is going to be probably easiest to calculate cost per BTU delivered.
For heat pumps the number of BTUs delivered depends on the air of the room where it’s moving the heat out of. If it’s a hot room, more BTUs are delivered to the water per kwh.

3 Likes
4

FlyingDiver:

You would need the new circuit even if going to a non-heatpump electric heater, so that’s kinda a wash.

Upside - they cool the garage slightly in the summer.

We wouldn’t consider going to a non-heat pump electric, we’d stick with gas.

Cooling the garage in Summer would be great, even a bit, but that makes me wonder:
1 - Cooling in Winter, when the garage is already cool (our low temps are in the 30s about a month out of the year). It might be forced to use the non-heat pump method to heat the water at that point.

2 - Our Summers are generally VERY dry, with humidity often in the 10-20% range, so I wonder how much it would struggle. OTOH, the air temp is VERY high, so lots of heat to pull out of the air.

Since our local utility is one of the entities offering a rebate on them, I guess I shouldn’t worry. They must work fine in our area.

5

foo1bar

What will be the BTUs delivered to the water for the different types?
ie. How fast will the water heater recover after using water out of it?
What’s the capacity (tank size)?
If the tank is big enough, and your needs are small enough, recovery speed may not matter.

Recovery is apparently MUCH slower than heating water by gas. But we’re just 2 people, and apparently it can easily handle 2 back-to-back 15-minute showers for a so-called 50-gallon tank. (As FlyingDiver said, the capacity is actually less than the rated amount, more so for these than other types. If that seems to be a concern, we could go for a 65-gallon, but that’s probably overkill and a waste of money, keeping an extra 15 gallons heated “just in case”. We’ll have to think hard about that one.)

Another disadvantage is that it’s a much more complex thing. I would not expect it to last 21 years. […] A heat pump has a compressor, an expansion valve, and all the pipes with refrigerant in them.
This is a big deal. At our age, 21 years will probably outlast us, so there’s a big appeal in not having to deal with replacing an expensive appliance when in our 80s.

3rd thing I’d look at is cost per BTU delivered.
Yeah, this is too tough. I did compare the yellow Energy stickers of 2 comparable models, which assumes a whole lot of unknown things. Plugging in our current average costs for gas & electricity, it appears the gas water heater is at least double the operating cost of a heat pump water heater. But there are so many variables and unknowns, that could be way off.

Thanks!

6

Hi KenAtPcs,

I looked at these about 6 months ago. I liked some of what I read about them but the noise thing was a problem.

These things work best in a “controlled” environment, a conditioned space.

You mentioned that it would have lots of heat available in the summer. In cool/cold weather, it won’t. Depending on the model, it may go to resistance heat. If it does have that, it may have a very long recovery time.

I checked with the two largest plumbing suppliers in town and neither has ever sold a heat pump water heater. When I asked why, both answered, “Noise.”

Since we are building an ICF home, noise levels inside are important.

So I bought an 85 gallon Rheem Marathon. It is sitting there waiting to be hooked up in the next few weeks.

Does that help you?

Gene
All holdings and some statistics on my Fool profile page
http://my.fool.com/profile/gdett2/info.aspx

4 Likes
7

2 - Our Summers are generally VERY dry, with humidity often in the 10-20% range, so I wonder how much it would struggle. OTOH, the air temp is VERY high, so lots of heat to pull out of the air.

Low humidity is not a problem for a heat pump - the low humidity just means there will be less condensate.

1 - Cooling in Winter, when the garage is already cool (our low temps are in the 30s about a month out of the year). It might be forced to use the non-heat pump method to heat the water at that point.

So what’s the low temp in your garage (where you’ll have this installed)?
Is it below freezing? I’m guessing it probably is not.
I suspect that most (maybe all) of the heat pump water heaters do not have a non-heat-pump method to heat the water. And at least the one I looked at, it says it should not be installed in a place where it gets down below freezing. (probably not an issue in your area inside a garage, since you’re saying low temps are only in the 30s for a month)

1 Like
8

I have a Rheem 50 gallon heat-pump water heater. I installed it when we bought this house; it was used as a rental for a year, and up to 4 people were using it at a time, nobody ever said they ran out. That said, I have no idea what the rebound time is because it’s never run out for us in the past 2 years either.

It is not “noisy” although it certainly makes more noise than an old electric or gas heater which have no moving parts. Reliability? No issues so far, but it’s barely 3 years in. I note that most water heaters die because the tank starts leaking, but then this thing has moving parts, so who knows? Of course I just posted about our Amana (I thought Kenmore but now I remember) refrigerator with much the same mechanics which ran fine for 25 years. The only thing that kept breaking was the ice maker and/or the solenoids controlling the water flow to the ice maker.

It does make a lot of cool air in the exhaust; I let it flow freely in the hvac room in summer, and direct it outdoors in the winter (simple vent baffle. Vent not necessary, but I was looking for something to do, so…)

I bought it on sale at Lowe’s, no rebate from TVA, but I’m glad I did anyway. Heat pump is vastly cheaper than resistance heating, and probably somewhat cheaper than gas. It has a digital control panel (of course) which means I can adjust it from afar, which I have never done and likely never will. It is more convenient that getting on my knees and opening a panel to adjust the temperature.

If you put it in a garage I would wrap the lower 2/3 in an insulation blanket to help with passive heat loss in winter. You shouldn’t wrap the top where the mechanics are, of course, but you knew that.

1 Like
9

I suspect that most (maybe all) of the heat pump water heaters do not have a non-heat-pump method to heat the water

Actually most of the ones I looked at do have a resistance heat backup, just as a heat pump hvac does. If that kicks in it’s no more expensive or have longer rebound time than a traditional electric water heater, because that’s how they heat in the first place.

So what’s the low temp in your garage (where you’ll have this installed)?

An attached garage will be about 20 degrees warmer than the outside because there is a certain amount of ‘bleed’ from the attached wall. A heat pump will work even in temperatures in the teens, it will just be less efficient than it would be at a higher temperature.

When I asked why, both answered, “Noise.”

I am surprised. I would have thought the answer would be “cost” because they are much more expensive, although you recover the cost over a few years’ time. As for noise, I cannot hear mine, although it is in an hvac room. I do hear either/both of the hvac units switch on, the fans switch on, but I never hear the HWH.

1 Like
10

Goofy I sense your heat-pump water heater is not in a typical garage. Also I believe you live in Tennessee – maybe on the Tennessee River. Would you mind sharing where your water heater is? If it is in the house can you provide a comparable noise level - is it like your refrigerator? a convention oven?

Since the water is heated by moving energy from its surrounding air to the water in the tank, at least in winter running a heat pump water heater has to increase your heating bill if the tank is in the conditioned part of your house.

1 Like
11

We have had a 50 gallon Bradford-White unit for the past 4.5 years. It has reduced our electric usage greatly. I can’t think of any reason why we wouldn’t have one again in the future. There is some noise when it is running, but as long as our basement door is closed (and since it is a trap door, it is almost always closed) we never hear it. The basement is a pretty consistent temperature, mid 50s in the winter & low 60s in the summer. It is always able to pull heat out of the air in the basement to heat the water and not change the temperature in the basement noticeably. We didn’t have to do anything to the electrical system, and the plumber was able to run the condensate line out to an old laundry drain. The only additional maintenance we do is vacuum the air filter once a month to keep it free of dust.

2 Likes
12

foo1bar
So what’s the low temp in your garage (where you’ll have this installed)?
Is it below freezing? I’m guessing it probably is not.
We usually have a few mornings a year when the temp is a few degrees below freezing outdoors (though in recent years, not so much). I don’t think garage is insulated (it is drywalled), but it is still warmer than outdoor ambient. Today was the first time I measured it, and it was 13F higher. But I don’t know for certain how that might translate when the outdoor temps are in the high 20s or low 30s. Great to know that low humidity isn’t a problem; I wasn’t sure, based on my limited digging so far.

Goofyhoofy
Thanks for that info. It sounds intriguing to have cool air in the Summer exhaust to our central hvac ducting (if that can be done). But then again, when we need it most (July & August), I doubt the water heater comes on enough to make that worthwhile. Sometimes our “cold” water is too hot!

We had an insulation blanket on our water heaters in our previous home (in the Pac NW). But when we moved here, we were told that given the thickness of the water heater walls and our temps, it would be a waste of effort. Yet I wonder; it’s cheap and easy to do, so I might as well.

GWPotter
If it is in the house can you provide a comparable noise level - is it like your refrigerator? a convention oven?
I’ve read several people compare the noise to that of a microwave oven (sans the beeps!).

13

Goofy I sense your heat-pump water heater is not in a typical garage. Also I believe you live in Tennessee – maybe on the Tennessee River. Would you mind sharing where your water heater is? If it is in the house can you provide a comparable noise level - is it like your refrigerator? a convention oven?

The HWH is in the same room with our two hvac (heat pump) units. They have giant fans to push the air through the vents, but no outside cooling fans because they’re geothermal (river water). As such there is a water pump (outside, don’t hear it) and a bunch of relays and water storage tanks (inside, don’t hear those either). It is an enclosed room, but we can hear when the hvac units switch on and especially when the fans come on. It’s in the basement directly under the library/guest room, but even in that room the noise is tolerable.

So last night I waited around until the HWH came on to listen for “noise.” (The things I do for science!) Right next to the HWH it’s as loud as ribbon filament spacer heater fan. Two feet away it’s audible but almost not noticeable. Ten feet away you’d be forgiven if you didn’t even know it was on. So yeah, maybe like a microwave oven.

Since the water is heated by moving energy from its surrounding air to the water in the tank, at least in winter running a heat pump water heater has to increase your heating bill if the tank is in the conditioned part of your house.

It’s air conditioned on both sides of the hvac room, but that room itself isn’t. But as someone on this very board pointed out to me, when I have the vent directed outside and expelling cold air, I’m lowering the air pressure which is probably compensated by attracting outside air in through the various leaks in the house enclosure, so it may not actually profit me much. If the exhaust is (oh I don’t know, 40 degrees, a guess) and I’m expelling it only to get 30 degree leakage back in, then it’s a bad trade, eh?

Still, the air that comes out is quite chilled, which is why I direct it in to the room during summer. It isn’t a reverse effect in summer because it’s the same air, just chilled.

But in the big picture, resistance heating is the most expensive form of electric usage - by far. So on balance I suspect heat pump water heat is a win.

1 Like
14

Goofy thank you for the detailed response -

Our HVAC is a heat pump - “multi-speed” Carrier Unit. Our house design allowed the builder to use either a gas or electric water heater. The electric water heater is in a cubby about 18 inches above the garage floor.

Our winters are mild and short (we live in Gainesville, GA) but I wonder about further cooling of the garage in from mid December through March.

15

Ran across a Rheem Training page that said if any of the stuff that can not be serviced by a plumber (heat pump, electronics, etc.) fails during the 10 year warranty period, they swap out the water heater. These water heaters connect to WiFi, so I am guessing Rheem would get a Heads Up that something was wrong/failing with the parts that are not normal plumber service items.

See this video - start at 28:15 and the Rheem trainer says if any part of the sealed system fails, they do a swap out. That said, it would be a lot more reassuring if such wording was in the warranty section.

https://www.youtube.com/watch?v=Eilf3gBT6s4

2 Likes
16

Since the water is heated by moving energy from its surrounding air to the water in the tank, at least in winter running a heat pump water heater has to increase your heating bill if the tank is in the conditioned part of your house.

“However, if placed in conditioned space, HPWHs will produce cool and dry air that is a benefit in the summer months but will lead to higher heating bills in the winter months.”
https://www.energystar.gov/products/water_heaters/high_effic…

1 Like
17

One of the main problems I would have is that there isn’t a floor drain in the garage. A condensate line would need to be run through the wall to the outside.

PSU

1 Like
18

Regarding the water drain.

We have one of these. Luckily, the utility sink is adjacent to the heater. Line was plumbed into the sink. If I had my druthers, I’d reroute the line to the drain so the sink is not partially occluded by a cpvc 1/2" line in the corner.

It hasn’t bothered me.

Cooling the garage is nice. Mainly for the humidity reduction (Florida).

Of course, that all goes out the window when the garage doors go up. (increasing both my discomfort AND the unit’s efficiency)

The unit is loud enough to be significantly louder than our refrigerators and deep freezers, but much quieter than the 3.5T unit outside or the 11.5 ton unit outside. Nothing compares to my cheap craftsman air compressor for noise, however. (thing runs 98 dB when cycling!)

I’m very happy with the purchase, but the economics are questionable for us. We had electric heated water before, the bill is less, but the unit was almost twice as expensive. The $250 credit helps, but, the unit must last 10 years or it will be a net loser. (almost in year 5, currently)

3 Likes
19

I’m very happy with the purchase, but the economics are questionable for us. We had electric heated water before, the bill is less, but the unit was almost twice as expensive. The $250 credit helps, but, the unit must last 10 years or it will be a net loser. (almost in year 5, currently)

Is the anode assessible?

For my gas water heater, the only difference between the 6 year and 12 year warranty water heater is that the anode on the 12 year heater is twice the size.

PSU

1 Like
20

We’ve had a Rheem heat pump water heater since 2017, and it’s worked great. We went with a large 80 gallon tank, and we keep the thermostat at a hot 135F. Ours is a “hybrid” unit, meaning it has resistive heat elements for backup, but I started it in “heat pump only” mode for maximum savings, thinking I’d change it to hybrid/mixed if needed. I haven’t had any reason to touch it. Recovery is plenty fast enough to keep up with our usage, even filling a large soaker tub while someone else showers. 80 gallons stored at 135F is a lot of hot water…

We had a resistive electric water heater before. The heat pump uses almost 30% of the electricity of a traditional electric heater (energy factor 3.5 vs 1.0), and that’s confirmed by my power bills, which noticeably dropped $25-30/month when we switched. Heat pump units were ~$1600 when we bought it, and there was a $300 energy credit. Saving $300-$350/yr in electricity means the unit easily paid for itself within 5 years.

The heat pump is installed in our garage, and is no louder than a typical refrigerator. You can hardly tell it’s on unless you put your hand in front of the cool air discharge vent. It has the added benefit of cooling the garage a little bit (in hot/humid FL) with that cool, dry, “waste” air.

3 Likes