Posted by: Peter Black | September 4, 2008

Geothermal Heat Pumps, suitable for most of the lower 48 and ready now

Geothermal Heat Pump Suitability in the Lower 48 States


Geothermal Heat Pumps, Geoexchange systems, ground source energy, etc. all refer to the same thing: an HVAC system that utilizes the stores solar energy in the shallow areas of the soil or in a pond to alternatively heat or cool a building. Since the soil temperature remains relatively constant throughout the year in comparison with air temps, there is a differential in most parts of the US most of the year which can be extremely efficient for heating and cooling.

So of course, I had to know if there are any regional variations inside the US which made these systems more or less suitable for a given area. Mind you, this does not mean that you should skip the site suitability analysis should you be interested in purchasing a GHP: this map relies upon data at a 5km resolution…far too coarse for a local analysis.

Here’s how I created the map. I downloaded a global soil temperature database from the USDA Then I used global temperature means, highs, and lows, to produce a suitability map of the difference between these variables. What that shows is the areas in gray have soil temperatures that don’t differ too much, on average, with the air temperature, lowering the effectiveness of a GHP system.

Today, there are over 1,000,000 Geothermal Heat Pumps installed in the US, which reduces our crude oil consumption by some 21.5 million barrels annually.



  1. I have done extensive research on replacing my air to air heat pump (AC unit) with a geothermal model, specifically the climate air two speed unit. There are only a handful of vendors in Houston who install these. I read your post, have you installed one and if so, what have your results been so far? Why not just tell people if Houston is a good or bad place for them, the soil temp will be about the same across the city.

  2. Hi Scott,

    It looks to me like the entire state of Texas, as well as most of the US, is ideal for geothermal heat pumps. You are absolutely correct: the soil temp a few feet down is pretty constant there. Relative to the outside air temps which I know fluctuate in the Houston area, these stable soil temps will provide enough differential to generate power throughout the year for you. However, it is highly recommended to have your home site surveyed by an expert since there are site level factors that could make or break your decision. The main point of this map is to point out that there is vast potential for these efficient systems to make a real dent in our nation’s energy budget.

    I haven’t installed one myself (would like to though)l, but I believe there are some excellent online resources for you to do more research:

    and there are plenty of Houston area installers and consultants:

    Thanks for the comment!


  3. That is a great article. Thank you for sharing.

  4. great article ! can you include the different types of heat pumps details and it’s price

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