Solar vs Heat pump vs Tankless

[cholcombe]

Hi Guys. So with the introduction of the new heat pump water heaters I'm having a problem figuring out which is the best to use. I have 1 bathroom, 1 dish washer and 2 people living in the house. Is there any website or study comparing the efficiency and cost of the 3? i also know this depends on how much water we're using... I don't think we're too horrible. I have a 1 gallon per minute shower head and I'm not sure what the dishwasher uses. We shower together every other day for 15 minutes so that saves on water also

[Daox]

IMO solar is the best option, its not cheap though. You'll still need a backup as well, and I think I'd personally go with a tankless unit for that.

[Patrick]

The latest issue of Consumer Reports had a review. They said the heatpumps were the best for cost and low payback time (3-5 years). Solar saves in the summer but not so much in the winter and is expensive. Tankless costs a lot and you have to wait for the water to arrive. Heatpumps maintain the water temperature and are relatively inexpensive. There is also a Federal Govt. rebate of 30% if you install a heatpump by the end of the year.

"Hybrids: Savings, even in winter
We tested the A.O. Smith PHPT-80, GE GEH50DNSRSA, and Rheem HP50RH in a 65° F test chamber to simulate a cool, Northeast basement—a tougher environment than the Sun Belt because there's less heat to extract. The A.O. Smith led with average savings of 59 percent, though the others came close. Before we could complete testing of a fourth model, the Stiebel Eltron Accelera 300, its heat pump stopped working; we've had it repaired and are putting it through our tests. But at more than $3,000 installed, it will have to save even more than the others to match their payback times.

Solar: Great in fair weather
Solar heaters supplement an electric heater by transferring the sun's heat via liquid that flows through a roof-mounted collector. None saved more than 32 percent over standard electric heaters in last year's tests. The Eagle Sun and Heliodyne we added this year qualify for Energy Star status. They also delivered stellar savings in sunny summer months: 82 percent for the Eagle Sun and 79 percent for the Heliodyne. But those savings plummeted to 28 and 35 percent, respectively, in winter. Another model, Sungrabber, could pay for itself as quickly as a hybrid heater, but like other solar systems, it's more complex.

Tankless: Expect a long wait
Instead of storing hot water, tankless heaters fire up a burner and run water through a heat exchanger to supply it when needed. Makers of gas-fired models claim they produce endless hot water and savings as high as 50 percent over gas storage-tank heaters. But in past tests they saved only $70 to $80 per year. Up-front costs of $2,000 to $2,400 with installation could push the payback time to 15 to 22 years—longer than most might last. And even if you install a gas unit before the federal tax credit expires, payback would still take eight to 12 years."

[Xringer]

A heat pump water heater needs to be installed in an area where the air temperature
isn't going to get very low.
My basement temperature, for example can get so low in the winter time, that
a heat pump is really going to have to work hard, unless it's pretty efficient.

The HP water heater I saw at Lowes might be a good design..
50-Gallon GeoSpring™ Hybrid Water Heater Item #: 79425 | Model #: GEH50DNSRSA $1,439.10
GE Appliances - GeoSpring™ Hybrid Water Heater Product Demo

It's pretty costly, unless you can get some of the cost picked up by the state/fed/taxpayers

In some areas, heating hot water with gas isn't a bad deal. Some of the
new heaters are very efficient.

I'm using a hybrid hot water system now. It's oil with a DIY solar PV heater..
Not at all efficient, but seems to work okay for two retired people.

[cholcombe]

I knew you guys would know this right off the bat! Thanks for the responses. Yeah I thought about the temperatures in my basement. I think it stays fairly warm in the winter, maybe 60-55 degree's at the coldest. The consumer reports finding were very interesting. I didn't think the return on solar would be so low in the winter. I like the idea of the heat pump because it's almost "plug and play" instead of doing all kinds of mods to the house to get solar working. But at the same time solar feels more green if that makes any sense haha.

[Xringer]

I had solar HW once and the tank and heat exchanger couldn't take the local water.
(Woburn water eats copper for breakfast).

The reviews for the Lowes GE ASHPWH (air source heat pump water heater!)
had at least one story of a $1,000 installer fee.. The homeowner looked at the
job and decided it was "plug and play" and DIYed it..

If you already have an electric HW heater, the GE type should just drop right in.
Just need a drain hose for condensate. It will dehumidify your basement.

55-60 isn't that warm. My old dehumidifier hardly works at 65 anymore.
Got a new one this summer. So far it's working well. Won't need it much
during cold weather..

But you really need to look at the Average temp down there.

I do like that GE and I'm started to wonder what it would cost me..

[Ryland]

I have a friend who installs solar hot water systems and does Bosch on demand water heater service, he pretty much told me that if heat pump water heaters live up to their claims or come down in price that he will have to either start selling them or change jobs because their claims out perform the claims of solar and if you ran your heat pump water heater off PV panels the installed cost would come in about the same as solar thermal.

[MN Renovator]

I thought about this a bit before. I look a look the price of the heat pump units and it looks like they would be great for environmental reasons or if you didn't have natural gas and your basement isn't very cold. I don't think they would ever pay off in energy savings, especially so if the unit rusted out in 10-15 years like most water heaters do anyway.

The tankless heaters seem to be more hype than anything, if I had no natural gas and wanted to go with a tankless setup of some kind I'd be inclined to have them be electric at every point of use so that way I don't have to run gallons of hot water just to get the hot water to me. I stayed at a buddies townhouse with a tankless heater once and you run the hot water, it gets hot, then cold, and then hot again because it sends you the 'puck' of heat in the exchanger but then takes awhile for the burner to get the water warm again so you end up using a whole bunch of water and possibly more gas.

I've been fairly satisfied with my gas water heaters cost, my gas bill is consistently 7 or 8 therms when I'm not using the furnace which includes the water heater and oven. It's about $15, or $6.5 after you remove the 'basic service fee' of $8.50. So about $80 a year in gas when I subtract the furnace usage to keep water at 125 degrees and take showers of 15-20 gallons with a Waterpik Ecoflow, an amazing 1.5gpm shower head on a daily basis (which I've measured to actually use 1.8gpm, close enough for me). This $80 is without any water heater insulation added to what the water heater already has.

A heat pump water heater wouldn't work well for me, the basement right now(ran around with a infrared heat thermomter) is 52.3 degrees right now and if I were to dehumidify my house, I would feel comfortable in the house at 50.2 degrees upstairs. I found that if I let the house drop slightly below the basement temperature the ground-sourced heat rises from the basement to heat the house and the furnace runs much less. So I can't cool the basement or dehumidify the house. Even without that extreme, if you live in a cold climate you would have to make up for that humidity in the house otherwise you would be cranking the heat up more to compensate or would need to find a way to add humidity to the house to make up for the humidity lost.

If your reasons are monetary and you've got natural gas in your house, I don't know how any other solution would be cheaper. Just be sure that if you replace your water heater, get one with a longer warranty and rated to use less gas because the ones with longer warranties typically also have more insulation built into them and a more dense heat ribbon running up the center exhaust stack to gather more of the heat that would otherwise go up and out of the house.

Solar on the other hand is probably the best bet if you get enough sun. I'm not sure how well it would work in a Minnesota winter but I'm sure it would help outside of the cold cloudy months.

[AC_Hacker]

Originally Posted by cholcombe

...i also know this depends on how much water we're using... I don't think we're too horrible...

As cholcombe correctly noticed, the amount of water used is very important in making this decision.

I live alone and don't use nearly as much water as an American family, so for this reason I decided to go with a tankless (Bosch Aquastar AQ 125 X, NG fired, D-cell flame ignition), and I have been using it for more than 10 years, maybe 15 years.

It is true that it doesn't give you 'instant on' hot water. The plumbing in my house was not laid out to favor efficiency, and the most frequently used outlet, the kitchen faucet, was the most distant outlet from the old tank-style water heater. I didn't know about the warm-up lag when I replaced the old tank unit with the new tankless unit, so a poor situation got worse, as far as convenience goes... also as far as water use goes too.

I'm in the midst of a bathroom/kitchen remodel, and I have relocated the kitchen sink closer to the tankless unit, and re-plumbed everything with PEX so the water no longer flows through right-angled paths. The upshot is that the distance from the most frequently used outlet to the water heater is now about 1/3 the distance it was formerly. The warm-up time has decreased considerably, saving water and vexation. I'm so happy with the result that I am even considering buying a very small propane tankless, converting it to natural gas and installing it right over the sink, at the point of use, like you sometimes see in foreign movies.

Regarding economy, my hot water expense has gotten much lower than it was when I was using a gas-fired tank unit.

I have a friend who has a Ground Source Heat Pump for heating his home. He has a gas-fired water heater, with a standing pilot, that is on standby and is used only for backup for his GSHP, when the temps get really low. During the summer this water heater just sits there, losing heat and burning gas thru it's pilot flame. I compared my gas use to his for this period, and my gas use during the summer with all my dish washing, long showers, hand washing, etc was lower than his with no use at all.

There are two lessons here:

• Standing Pilots Bad
• Tankless Water Heaters Good

I have had virtually no problems with my water heater in the time I have owned it. The D-cells last about 2.5 years before they need to be replaced. An unexpected benefit of the D-cell ignition is that when power goes out, as it does from time to time here, I can still take a hot shower.

I have come to understand that the tankless needs to be flushed out with white vinegar every year or two, to insure a long and happy life. I haven't done that ever, and recently I have been having a bit of a starting problem, so water heater flushing is on my to-do list.

So, as a user, I've been pretty happy with this unit.

If I were now deciding to go tankless, I would investigate the outside units, as they offer the possibility of mounting very close to the most frequently used outlet, and also solve the venting problem without making more large holes in the house envelope. I would also put a large water filter ahead of the unit, and don't forget the sediment flushing set-up.

* * *

As an aside, I have been experimenting with reducing the amount of my home that I heat, heating just the room I occupy and I have learned that there is considerably more heat movement through walls than I would have previously guessed. What I'm getting at is, if a heat pump water heater is placed in a garage that is attached to the main house, there will be more heat movement from the house to the garage than previous, since the HP water heater will be reducing the temp of the garage air. So, what is saved in water heating, might be lost to some degree, in home heating.

Best regards,

-AC_Hacker