Indirect vs Electric water heater

you have asked about cost but then you mention your issue with running out of hot water.

a heat pump water heater is the cheapest.

But the indirect should recover faster. Of course you’ll be paying to heat up your boiler all summer which I find to be insane.

Get your wife a low flow shower head and an 80 gallon tank

if you can identify the DHW load, then size the tank to that. A 30 minute shower with a 1.5 gpm shower head?

40-50 gallon Indirects cover most households, you can run them at 140 and add a mix valve to extend the drawdown capacity. Your boiler output has a lot to do with recovery time.

If you had an 80 gallon tank would your wife take a 45 minute shower?

For endless hw, a tankless is an option.

https://www.efficiencymaine.com/at-home/water-heating-cost-comparison/

Hi, Can you tell us the size of the tank, and using a bucket and stopwatch, measure the actual gpm of the shower… then let us know that number as well. I'm pretty sure those numbers will help us give you some solid ideas. 😊

Yours, Larry

At $.102/kWh, the energy used to create the same amount of hot water as the boiler/indirect would cost approximately $2.69 compared to $.68 for NG. Using an electric WH with prices like that is insane, in my opinion. An example of 100 gallons per day with a 70 degree temp rise would be a difference of roughly $39 per month. 5 years your indirect is paid for and you're saving $468/yr after that.

A comment on heat pump water heaters. Wonderful gadgets. Expensive to buy and maintain, but wonderful on energy.

With a problem. Their recovery rate is abysmal. Unless you engage the resistance element (which some, but not all, have) it will take, quite literally, hours for them to reheat the tank (the resistance elements are, of course, quicker — but then you might as well have a straight electric…). What this means, in practice, is that what you have for hot water in the morning or the evening is what there is in the tank, and no more.

Now if you are a two person household and go for Navy style showers with a piddly 1.5 gpm shower head, this may work for you. Otherwise, maybe not so much.

Important note: please remove the contractor quoted price from your original post. we don't publish that info on this site: It is in the rules https://heatinghelp.com/forum-user-manual/ …about the 4th one down.

you can use the EDIT function to remove that price: and substitute $$$$ in it's place.

@ethicalpaul will always direct you away from an indirect even if the number don't add up. I did a comparison for a heatinghelp.com member just last month.

They were in a similar situation. They already owned the indirect and wanted to purchase something else because they were getting a heat pump to use for 10 months out of the year (Cooling and the start and end of the winter). the two coldest months were going to be covered by the existing hot water boiler using the baseboards. The HH member was going to shut the switch to the boiler off for the 10 months that he didn't need the gas boiler, so there would be no heat for hot water fof the indirect. I understood the logic and still found that the indirect was the best option.

I said it then and I said it in 2024.

If you click on the link to the chart you will see this chart:

This is what an accountant might call a cost-of-ownership calculation.

1. The first column lists the number of years you plan on owning your home (this example goes to 30 years).
2. The second column shows the lowest-cost water heater at $1,200.
3. The third column is the estimated annual fuel usage (not accounting for inflation).
4. The fourth column represents a high-efficiency water heater.
5. The fifth column is the annual operating cost for that unit (not accounting for inflation).
6. The sixth column is for an indirect water heater (not vented), assuming you already own a high-efficiency boiler.
7. The seventh column is the annual operating cost for the indirect (not accounting for inflation).

This assumes only the additional cost to produce domestic hot water—fuel used for space heating is not included, as it would not be considered for the other two water heaters.

Let’s analyze the numbers:

On average, a standard tank-type water heater lasts about 10 years, so you could expect to buy three over a 30-year period for both the lowest-cost model and the more efficient model. That comes to $3,600.

The same is true for the second option, for a total of $5,400.

Many indirect tanks come with a lifetime warranty. Since there is no flame inside the tank to contribute to corrosion on the dry side, they tend to last much longer. That brings the total to about $2,400, since you would likely only need one tank over the 30 years you own the home.

Now, take the annual fuel cost over 30 years and add it to each total. You’ll see that the most expensive choice upfront—the $2,400 tank—actually costs less over time.

What choices are you thinking about? I will make up a chart for you using real time data and the estimates you have in hand to help you decide.

Get a boiler with a tankless coil and pipe the domestic through the coil and into an electric water heater. I’ve done it a couple times. Not my finest moments. Never heard back from those clients though so I assume it worked out.

@ethicalpaul I believe this says what you believe:

That word “insane” was my clue to your opinion about using a boiler to heat water in the summer. You’ve made your position clear on this topic every chance you get. I don’t think it’s a misquote—you don’t believe a boiler should be used for DHW.

Your heat pump water heater stays hot all summer long. My boiler does not stay hot all summer long. Those facts aren’t really in dispute. When I use that large boiler—big enough to heat my entire house in New Jersey on the coldest day of the year—it still has to fire up just to make a small amount of hot water for my indirect tank. Even so, it ends up costing a little less or about the same as what you might pay to make that same hot water with your heat pump.

I guess I’ve had too many bad experiences with heat pumps that didn’t perform well for heating homes in New Jersey. After dealing with customer complaints about no heat in January—and being outside trying to add refrigerant in below-freezing weather—it’s made me less enthusiastic about heat pumps.

You were the first one to reply to this discussion and you said "HeatPump Water Heater"

And the OP switched from oil to gas and didn't get the savings they expected. How do you account for that?

What does your chart say about this option? Fill in the AFUE of the WM GV90+ at 91.0% got the EF number in your chart.

This represents the question originally asked.

I've tried hard to find the amount of power a HPWH puts out, and I've come up with almost nothing.

ASSUMING it's 4,000 btu/h which seems very possible, that results in a 6 hour recovery time after I take a shower vs my NG tank heater that takes roughly 30 minutes. This is assuming a 50f to 140f rise of 25 gallons. That's also assuming I did the math correctly.

A 6 hour recovery will work for some, and won't work for others.

If anyone actually has info on how many btu/h these typical residential HPWH are, I'm curious. Input wattage for the compressor would be a good starting point.

Seems to me the only really valid conclusion is this: every single situation is different, and thus it would be dubious to say that this one or that one is best because it seems to work for this particular situation.

What we can do — and are trying to do — is to point out various factors which should be taken into consideration in making a choice. Just two examples from my own experience. First, someone up there said that there boiler only runs two moths out of the year. Don't I wish. Cedric — which only does heat, supplementing two mini-split heat pumps — runs 9 months out of the year (in fact, he is running as I type on a sunny May morning!). And we need all the capacity of the oil fired water heater. One of the houses I care for is owned by a moderately wealthy individual. She installed a heat pump water heater (she had had oil). It worked well — so long as the only person there was herself. When she had guests, it didn't, so she went back to the oil fired one. Should I have told her and her guests to take short low flow showers and skip more or less daily clean linens? Ah… no, if I wanted to keep my job.

So — in those two particular situations, a heat pump water heater didn't work. But — in other situations it would have worked splendidly, though with New England electric rates it wouldn't save any money. There is, for example, an island resort (summer only) I know which uses a bank of heat pump water heaters. They have ample solar panels, and can control when guests can use the hot water — and getting oil to the island is insanely expensive. The heat pumps do the job well, and were much the best choice for the application.

So. Every situation is different. How do you — or your client — actually use water? How much does energy cost? Even installation questions? Do your sums — and then pick the best solution.

That comes out to roughly 5000 btu/h.

Do the larger ones have larger heat pumps on them too or just resistive heating added?

I used 50f but I also only did 25 gallons out of 50. I did this because the incoming water can easily be 50 especially in the winter.

… and used the word "Insane"

He also mentioned the cost of installing the indirect water heater which was very reasonable in my opinion. (before he edited it out after I mentioned the rules about that type of thing)

You paid for a HPWH and got the federal rebate (which is no longer available as of right now) and I cant believe the tank that costs more from the wholesaler than an indirect water heater, would be less expensive to install than the indirect. But we have different perspectives and experience on this topic. When you were looking for a water heater I guess you looked as more than just HPWH. I might guess that you got a price for an indirect for your steamer (not recommended) and for a tankless on demand and perhaps a chimney vented. then you DYI your steamer and perhaps the HPWH after you discovered the rebates and tax incentves. You selected the best one for your situation. I believe it truly is the best for you.

Also What was the ten year cost for the indirect with the GV 90+ at 91.0% AFUE?

Hay @ethicalpaul I did some research on a Rheem GEN 4. The “Recovery (GPH)” shown in the specification chart is NOT heat-pump-only. That number is based on hybrid operation (compressor + elements). You mentioned that you set yours to heat pump only. I did some math and the compressor will rase the temperature of water to 130° from say 40° incoming city water at a rate of about 5.6 GPH. If you have the 80 gallon tank and don't use any hot water after filling the tank with cold city water, then start your compressor, at a rate of 5.6 GPH it should take only 14.2 hours. That is not ever a full day!

I believe that might not work for our friend who is complaining about running out of hot water. What would you recommend in this case? More tanks?

Then you have the smaller tank. If you have the 40 gallon model it will only take a little over 7 hours. But then, you have only 40 gallons of hot water to use.

I wouldn’t want to be on the other side of that argument with this one.

She looks like a force to be reckoned with.

As far as I'm concerned she can have as much hot water as she wants!

I like it when she is smiling like that

Id expect it's because it's just going to float up there on its own anyway and mix everything. This way you're filling the tank with hot water from the top down and pulling the cold out of the bottom, not really mixing anything.

The colder the water is the better the heat pump does.

A nice honest first hand experience, thanks!

Yeah,

I'm not sure why that was any different than your comments on the subject. You've given many reviews etc.

Some could argue yours is second hand experience though……….

Why so sensitive? We all enjoy your related experiences.

@Robert_25 with 575 posts is just a fresh voice on the question.