Ground-Source Heat Pump: Expensive Boiler Replacement Option

By: Scott Gibson , Contributing Writer
In: Old Houses, Home Improvement Tips, Green Renovations

Old House Q & A:

We live in an old house in upstate New York and we’re thinking of replacing our very old boiler with something more efficient. Winters are pretty cold here. We keep hearing how wonderful ground-source heat pumps are. Is this a good option for an older house?

Possibly. Ground-source heat pumps are attractive for a couple of reasons. They don’t burn any fuel to produce heat, at least not directly, and heat pumps can cool your house as well as heat it. They’re also more efficient than many conventional boilers and furnaces.

Ground-source heat pumps work like a refrigerator in reverse to absorb and concentrate small amounts of latent heat gathered from the earth or a body of water. Heat pumps, like refrigerators and air conditioners, rely on something called vapor compression to work.
Even in winter, the earth is relatively warm six or seven feet below the surface. Tubing filled with a non-freezing liquid pulls some of the heat from the ground and carries it to the heat pump. The tubing can be placed in horizontal trenches, or in vertical wells.

If you live near a pond or stream, water also can supply the small amount of heat that’s needed for the heat pump to do its magic.

Efficiency Is the Name of the Game
Energy efficiency is one of the biggest advantages of a ground-source heat pump. For every unit of energy it consumes to run circulation pumps and the compressor, the heat pump produces three or four units of energy in the form of heat. This is what manufacturers call the “coefficient of performance:” the higher the number the better.

By contrast, electric baseboard heat is about 100 percent efficient, and the best gas furnaces on the market are about 95 percent efficient. Getting a lot of heat for the buck is why ground-source heat pumps get such rave reviews.

Ground-Source Heat Pump Caveats
First, there’s all that tubing that must be put in the ground–hundreds of feet of it. If you choose horizontal trenches, you’ll need a very generous back yard. The excavation equipment your contractor will bring in won’t be kind to your lawn or your gardens.

Drilling a new well for the tubing is another possibility, and a practical choice when you live in town. You won’t need nearly as much open land, but drilling a well can be pricey. If you already have a well that produces lots of water it may be possible to tap into the supply for your heat pump, but that’s a long shot.

Ground Source Heat Pump -- photo c/o Treehugger

Ground Source Heat Pump -- photo c/o Treehugger

Because installation is so much more involved, ground-source heat pumps typically cost a lot more than other kinds of heating systems.

If you can handle the cost and want the option of central air conditioning, a heat pump might be just right for your situation. Another option is to wait until the new generation of cold weather air-source heat pumps becomes more available. You’d get many of the same benefits, but at a lower cost.

For now, replacing you aging boiler with a high-efficiency gas boiler would be less disruptive to your house, and to your wallet.

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  1. 8 Responses  to “Ground-Source Heat Pump: Expensive Boiler Replacement Option”

  2. Aug 29, 2011
    Heat pumps really are earth savers, they can provide a lot of savings and they also lessen the carbon footprint of your home. Though installation can be quite expensive, it will last long and the savings you get from it will basically pay off your expenses.
  3. Aug 29, 2011
    GSHP is the only option of energy saving water heaters for this qustioner, I think. The reason is that he/she lives in a cold area. If not, Air water heat pumps is also an option. But for him, only GSHP. (solar can't make heating stably in bad weathers.)
  4. Aug 29, 2011
    I don't know people buy the ordinary heat pumps when they have the choice to select Geothermal Heat Pumps . Its absolutely pollution free and works in every climate !
  5. Aug 29, 2011
    A ground source heat pump extracts ground heat in the winter (for heating) and transfers heat back into the ground in the summer (for cooling). Some systems are designed to operate in one mode only, heating or cooling, depending on climate.
  6. Aug 29, 2011
    That is a great explanation of heat pumps. Thanks for sharing.
  7. Aug 29, 2011
    Whats more important is securing the air and thermal boundries of the home envelope. In many cases the "sizing" of the new tech heating and cooling systems can be reduced by as much as 1/3. Thus reducing the initial outlay for a new heating and cooling system. Look into an energy audit for your home and upgrade things like insulation before installing a new system.
  8. Lucy
    Aug 29, 2011
    And according to the US dept of energy additional costs are returned in energy savings over the course of 5–10 years.
  9. Kerry Hoffman
    Aug 29, 2011
    Totally agree that ground source heat pumps, like geothermal pumps, are super expensive -- between $10,000 and $25,000, and even more, but there are tax credits available. E.G. if a homeowner pays $15,000 for a geothermal heat pump system a tax credit of $4,500 could apply.