# heat pump water heater? **URL:** \ **Category:** Factual Questions\ **Created:** [September 16, 2012, 4:15pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879 "2012-09-16T16:15:00Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![bobsmom101](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobsmom101/32/2867_2.png) [@bobsmom101](https://boards.straightdope.com/u/bobsmom101)\ **Post date:** [September 16, 2012, 4:15pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/1 "2012-09-16T16:15:00Z")
Has anyone out there had experience with “heat pump” type water heaters? I have an all-electric house and the electric water heater really sucks up the power. I’ve read that the “heat pump” type water heaters are more efficient and am wondering whether their extra initial cost is worth the lower energy use. The alternative is solar panels. Thanks! ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [September 17, 2012, 9:36pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/2 "2012-09-17T21:36:54Z")
I’m not familiar with that type of unit, but we installed a [tankless on-demand water heater](http://www.rheem.com/products/tankless_water_heaters/) that is extremely energy efficient and that has the added benefit of not having a tank to rust out and dump 50 gallons of water into your basement. The disadvantage is that while the tank is relatively inexpensive, you may have to have a separate gas line run to it from your meter, which can cost some bucks. They do make electric models, however. ---
**Author:** ![bobsmom101](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobsmom101/32/2867_2.png) [@bobsmom101](https://boards.straightdope.com/u/bobsmom101)\ **Post date:** [September 17, 2012, 10:02pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/3 "2012-09-17T22:02:05Z")
> [@Chefguy](#): > > I’m not familiar with that type of unit, but we installed a [tankless on-demand water heater](http://www.rheem.com/products/tankless_water_heaters/) that is extremely energy efficient and that has the added benefit of not having a tank to rust out and dump 50 gallons of water into your basement. The disadvantage is that while the tank is relatively inexpensive, you may have to have a separate gas line run to it from your meter, which can cost some bucks. They do make electric models, however. Thanks chefguy, but I haven’t seen any electric tankless models that can handle water for a whole house (I don’t have gas or propane). Here’s a Rheem heat-pump model. They are also called “hybrid” water heaters: [http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?productId=202552735&storeId=10051&langId=-1&catalogId=10053&ci\_sku=202552735&ci\_kw={keyword}&kwd={keyword}&cm\_mmc=shopping-\_-googleads-\_-pla-\_-202552735&ci\_gpa=pla#.UFedT65wy1g](http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?productId=202552735&storeId=10051&langId=-1&catalogId=10053&ci_sku=202552735&ci_kw=%7Bkeyword%7D&kwd=%7Bkeyword%7D&cm_mmc=shopping-_-googleads-_-pla-_-202552735&ci_gpa=pla#.UFedT65wy1g) ---
**Author:** ![Emtar\_KronJonDerSohn](https://avatars.discourse-cdn.com/v4/letter/e/58956e/32.png) [@Emtar\_KronJonDerSohn](https://boards.straightdope.com/u/Emtar_KronJonDerSohn)\ **Post date:** [September 17, 2012, 10:34pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/4 "2012-09-17T22:34:56Z")
I’ve heard good things about them but I don’t have one. I have always wondered how much maintenance they would need. It seems the heat pumps on my roof need an annual checkup and cleaning and I can’t repair anything myself because I don’t have an EPA freon cert. If you are in the right climate to make solar water heat work I’d recommend looking into it. The initial investment is likely less than a heat pump water heater and it’s basically free hot water. When I was a kid we had panels that worked with our standard electric water heater. We had a timer to heat water electrically for an hour or two in the morning for hot showers and all other times were solar. It was mostly hobbled together parts that came with the house and it saved around $40/month for 17 years. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [September 17, 2012, 10:51pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/5 "2012-09-17T22:51:49Z")
> [@bobsmom101](#): > > Thanks chefguy, but I haven’t seen any electric tankless models that can handle water for a whole house (I don’t have gas or propane). Right. They would be point of use heaters, so you’d have to install one for each bath, the kitchen and laundry, at a couple hundred a pop plus wiring. Still beats tank heaters, IMO. ---
**Author:** ![Sir\_T-Cups](https://avatars.discourse-cdn.com/v4/letter/s/ed655f/32.png) [@Sir\_T-Cups](https://boards.straightdope.com/u/Sir_T-Cups)\ **Post date:** [September 18, 2012, 6:51pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/6 "2012-09-18T18:51:50Z")
[Shameless self plug](http://blog.safepact.com/general/energy-savings-guide-part-four-bringing-the-water-heat/) The “too long didn’t read” thing to take away from that is that the on-demand ones are great, but not really powerful enough to do your whole house, you would probably have to get two…one for appliances and one for showers’n’such. Solar power (IMO) is cool in theory, but it’s harder to maintain for the cost that you’re inputting to put it in your roof and wire it to your water heater, so I’m not a fan. ---
**Author:** ![Emtar\_KronJonDerSohn](https://avatars.discourse-cdn.com/v4/letter/e/58956e/32.png) [@Emtar\_KronJonDerSohn](https://boards.straightdope.com/u/Emtar_KronJonDerSohn)\ **Post date:** [September 19, 2012, 12:20am UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/7 "2012-09-19T00:20:17Z")
> [@Sir\_T-Cups](#): > > Solar power (IMO) is cool in theory, but it’s harder to maintain for the cost that you’re inputting to put it in your roof and wire it to your water heater, so I’m not a fan. I’d be interested to know what maintenance you’re talking about. You put a collector on the roof and run water through it. It heats that water with radiation from the sun to supplement electric or gas heated water. If you design the system to circulate with natural convection it has no moving parts and it’s the closest thing you can get to free energy. Are you thinking of photovoltaics by chance? ---
**Author:** ![Sir\_T-Cups](https://avatars.discourse-cdn.com/v4/letter/s/ed655f/32.png) [@Sir\_T-Cups](https://boards.straightdope.com/u/Sir_T-Cups)\ **Post date:** [September 19, 2012, 5:46pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/8 "2012-09-19T17:46:04Z")
> [@Emtar\_KronJonDerSohn](#): > > I’d be interested to know what maintenance you’re talking about. You put a collector on the roof and run water through it. It heats that water with radiation from the sun to supplement electric or gas heated water. If you design the system to circulate with natural convection it has no moving parts and it’s the closest thing you can get to free energy. Are you thinking of photovoltaics by chance? Actually no. What I was going on was setting up the panels on your roof to power a separate circuit that you would use to power your conventional water heater or on-demand. I honestly had no idea that it was possible to do the whole thing that you mentioned which yes, is way way easier than the convoluted way that I was envisioning ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [September 19, 2012, 10:09pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/9 "2012-09-19T22:09:18Z")
most of the energy in heating water is done in bringing it from well or water main temperature up to usage temperature. once at usage temperature it takes less heat to maintain it there. solar hot water collectors circulate a fluid (nonfreezing if needed) and use that to heat a storage tank of water through a heat echanger. that storage tank is then the ‘cold’ water input into your fossil fuel/electric water heater. so you are preheating the input water, it might be totally up to usage temperature at that point on sunny days. no heat pumps in the system just circulating pumps. this might have a payback of about five years with fossil fuel water heating. ---
**Author:** ![Enkel](https://avatars.discourse-cdn.com/v4/letter/e/df705f/32.png) [@Enkel](https://boards.straightdope.com/u/Enkel)\ **Post date:** [September 22, 2012, 6:49pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/10 "2012-09-22T18:49:00Z")
Silly question, but have you insulated your existing heater and pipes? You loose a lot of heat in the pipes (think of running 1/4 gal of cold to get heated water and that 1/4 gal of cold water sitting in your pipe will run to the lowest level and that is usually your water heater’s tank where it has to be heated all over again). Second, if you put a fluid on your roof for solar, keep in mind the weight you’ll be adding. If you’re were it snows a lot, that weight will be added to your snow loads as well. Each gallon of water/fluid is 8 pounds. Also, keep in mind that there will not be solar at night, so in most areas of the country, the fluid will have to be something that won’t freeze and burst the pipes over head. ---
**Author:** ![bobsmom101](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobsmom101/32/2867_2.png) [@bobsmom101](https://boards.straightdope.com/u/bobsmom101)\ **Post date:** [September 22, 2012, 7:08pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/11 "2012-09-22T19:08:51Z")
> [@Enkel](#): > > Silly question, but have you insulated your existing heater and pipes? You loose a lot of heat in the pipes (think of running 1/4 gal of cold to get heated water and that 1/4 gal of cold water sitting in your pipe will run to the lowest level and that is usually your water heater’s tank where it has to be heated all over again). > > Hi Enkel – the tank is heated but not the pipes. One reason I was interested in the heat pump water heater is that the pipes run through the attic and in the summer even the cold water is too hot to take a shower unless I let it run a while. If I could put the heat exchanger in the attic my problems would be solved (at least in summer). > > Second, if you put a fluid on your roof for solar, keep in mind the weight you’ll be adding. If you’re were it snows a lot, that weight will be added to your snow loads as well. Each gallon of water/fluid is 8 pounds. Also, keep in mind that there will not be solar at night, so in most areas of the country, the fluid will have to be something that won’t freeze and burst the pipes over head. Not a problem where I live; the temperature rarely falls below freezing, but thank you for the heads up! ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [September 22, 2012, 8:09pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/12 "2012-09-22T20:09:28Z")
a collector panel holds about 1 gallon of fluid. a collector panel weighs 100 to 150 pounds. ---
**Author:** ![neilzero](https://avatars.discourse-cdn.com/v4/letter/n/fbc32d/32.png) [@neilzero](https://boards.straightdope.com/u/neilzero)\ **Post date:** [October 15, 2013, 4:26pm UTC](https://boards.straightdope.com/t/heat-pump-water-heater/634879/13 "2013-10-15T16:26:43Z")
People who know recommend roof top solar water heaters when the roof is not shaded and the local has sunshine almost every day. A south facing roof is best and most use water with antifreeze to transfer the heat. North of 45 degrees latitude you will have to suplement the heating by some other means in December. All three heat pump type water heaters are still rare in Jacksonville, Florida. You could likely add some tubing to most existing central air conditioning units to get some pre heat for other kinds of water heaters. but as far as I know no one makes these, probably because they work poorly in cold weather. In theory refrigerators and deep freeze can also provide pre heat water. Similar systems extract heat from well water, or ponds of water. The third type gets hot water from deep wells (extremely deep in most locations) which is cooled by the heat pump. This is called geothermal heat. Neil