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I want to save money on heating bills. Residential heat pump systems cost thousands of dollars, which I can't afford. I am considering using a heat pump marketed to chill water for cooling CNC lasers (about $600). These have a 0.5HP-0.9HP heat pump inside, which discharges heat into the surrounding air.

Here is my situation:

  • My house has a shallow well (50ft) with plenty of water, so my water is basically infinite and free.
  • The water comes out at 54°F all year round.
  • I want to keep my house around 65°F
  • Typical outdoor low/high in Winter is 35°F/65°F

My proposed solution is to leave the water chiller in my living room, hook up a water hose to the water cooler, and let it discharge cold water to a hose running outside.

My thinking is that all of the energy the chiller uses (about 1kW) will dissipate into the living room, along with whatever heat it extracts from the water. I have to pay the 1kW in electricity, but the heat extracted from the water is free.

Am I thinking about this correctly? I would appreciate any advise about how best to implement this.

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  • You forgot the (energy and $) cost of pumping the water, unless you happen to be in the very tiny fraction of wells that don't need a pump.
    – Ecnerwal
    Jan 8 at 19:24
  • I didn't forget. I get 11 GPM and my pump eats 1.5kW. Electricity costs average 25¢/kWh here. That's 8182 joules per gallon = 6120404 joules per 100 cubic feet = 1.7 kWh per 100 cubic feet = 42.5¢ per 100 cubic feet. So it's negligible. Jan 8 at 19:56
  • Put differently, it's 0.015¢/kg of water pumped. If I cool each kg of water by 5°C (as the cooler I'm looking at can), then I get 21 kJ per kg = 0.0336 kWh / kg. That's 0.45¢/kWh. Propane costs $3.80/gal = 14¢/kWh, and electricity costs 25¢/kWh. Jan 8 at 20:13
  • Looks like you might be well on the way to writing your own answer, then.
    – Ecnerwal
    Jan 8 at 20:24
  • 1
    @AndrewCone That may be assuming the use of a glycol/water mix. Jan 11 at 6:33

1 Answer 1

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Practical issues

  • It may be loud (I'm guessing that you don't have it on hand yet to test-run) and that may be annoying in your living room.
  • It may leak. Things with water sometimes do. You'll have to take care that it does not, or that if it does, the leaks are caught and redirected safely to somewhere that is not a problem (such as outside with the rest of your wastewater.)
  • Appearance - it may not suit the aesthetic sense of your spouse/partner/housemate (if any,) your guests, or even you, for things that take up space in the living room.

You can put a nice furniture-type box around it, with a waterproof bottom in a tray-shape with a drain attached. You could also relocate it to the basement (if any) and just direct the warm air to the living room. You can line the inside of the enclosure with sound-dampening materials.

  • There will be a lot of water discharged over time - give thought to where it goes, so it does not create problems.

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