Greetings,

We've had our geothermal waterfurnace heating our home and part of our hot water for about a year and a half.  We're more than happy with it and now we are thinking of replacing our propane DHW tank with a heat pump tank.  We have our eye on the $1599 GE GeoSpring and are waiting for Obama's Homestar program to kick in.  The Homestar program is supposed to pay 50% and there would also be a 30% tax credit. We have a 40 gallon preheating tank that feeds into our 40 gallon propane and when the geo is running it supplies over 110° water most of the time.  I'm estimating that we used somewhere around 110 gallons of propane in the last 12 month period. Tank rental is $60/year and we paid a premium of $3.10 gallon because of the low volume.  The current DHW tank is in the basement which is "kind of" an unconditioned space.  There is no direct return of our forced air heating system although we did cut in two hot air supplies in the duct work that keep the basement a minimum of 55° in the cold months (we're in northeast wisconsin).  We have a modest use of water with 2 of us and frequent weekend guests (our kids bringing laundry home !!).  Our electric rate is $0.12 Kwh. My question is:  Do you think this idea will result in lower water heating costs for us or do you have any other suggestions/considerations ?

Thanks for your response
BadgerBoy [script removed]

At 80% off for the unit and $400/year in propane, I can say yes without using a calculator.

I do not understand why most geothermal heat pumps do not include the heat exchanger necessary to provide full water heating (even when the house needs no heating or cooling).

If all you are using propane for is DHW, then I think it may be worth getting rid of it. Now if you have a gas cooktop and maybe fireplace or dryer, that is different.
If your geo is giving you 110 degree water most of the year, I'd stay electric. An extra water heater blanket and pipe insulation may be more economical

Its good that you are upgrading your tank well i just wish to say you very best of luck for your plan.

110 gallons of propane X 93,000 btu/gal *70% efficiency = 7.1 million btu’s for hot water per year not including preheat
If you used an electric tank to get that it would take 7,100,000/ 3412 btu/kwh= 2100 kwh * 0.12$/kwh = 252$ per year
You are paying 110 x 3.10+ 60$ so that is 400$. Even a regular electric heater is a bargain compared to propane.
The energy factor of the ge unit is (2.35) can’t figure out what temp that is based on. But theoretically it could cut your hot water bill to 252$/2.35 = 107$ per year
Figure ½ the year you are heating with the geothermal system so that means you have to add back about 3.5 million btu’s per year from the geothermal system to the basement so figure a cop of 3 that is 3,500,000/3412 *0.12/3 = 41$
You are primarily in a heating climate. If you are conditioning that space with geothermal, then taking that heat and putting it into the watertank, therby cooling the basement requiring more geothermal to heat the basement, this is an inefficient way to generate hot water. You are basically running 2 heat pumps to heat the water, each with its own losses.
So my ½ assed ballpark guess is that with the heatpump hot water, you pay around 148$ per year, not including geothermal preheat tank, electric resistance heat would be 252$ Propane would be 400$
Now in a cooling dominated climate, the water heater helps you by cooling the basement, and makes a lot of sense( to me)

I think I would pick a very efficient electric(resistance) unit and not worry too much.
ymmv

Cheers,
Eric

I have the GE HP heater and geothermal with a dedicated buffer. It works well so far. Installed last summer. I leave it set so it only runs in HP mode.

With all the rebates and incentives the HP heater may not be such a bad deal vs a std electric tank. It also works as an effective basement dehumidifier in the summer. In your climate, the HP water heater run times during winter are low due to the geo heating the preheat tank so good. It can also be switched to just run the elements, if the basement is getting overcooled in the winter.

For your case I think going full electic vs HP electric is dependant on the rebates/incentives

I really like the look of this:

http://www.eviheat.se/upl/files/14983.pdf

Everything in one.