Heat Pumps (for non-specialist citizens)

Executive Summary:
  • "air conditioner" is the colloquial-consumer name used to describe an air-cooling appliance.
    • Technically speaking, most air conditioners fall under the label of "air-to-air" heat pump.
  • "heat pump" is the colloquial-consumer name used to describe a dual purpose appliance which can produce heat in winter then cool during in summer.
    • Technically speaking, anything that moves heat from one place to another can be called a "heat pump"
  • Heat pumps with their outside loops connected to soil (rather than air) go by the name of ground-source heat pumps.
    • when in heating mode during the winter, the soil 2m (6f) below the surface provides much more heat energy (typical temperature: 10C/50F) than outside air (0C/32F) ever could
      • when air-source heat pumps are unable to keep up on cold days, most usually energize one-or-more banks of electric heaters
    • when in cooling mode during the summer, a ground-source heat pump can more easily move indoor heat (typical temperature: 21C/71F) into a ground loop (10C/50F) than an air-to-air heat pump can move indoor heat into outdoor air (30C or 86F)
      • technically speaking, ground-source is a misnomer when in cooling mode; ground-sink would be more accurate
  • When real-estate is plentiful (think farm) most ground-source installations will employ a field of horizontal loops
    • the length of the loop is dependent upon local conditions. Moist soil will always transfer heat to/from the loop than dry soil so can employ shorter loops
    • the installer must do a soil survey before writing an installation quote
    • heat extracted from a too-short loop will eventually freeze the loop
  • When real-estate is scare (think city) most installations will employ one-or-more vertical loops. This involves drilling (typically 18m/60ft to 36m/120ft) which can be more expensive than horizontal loops.

Prologue (2018.12.xx)

I just read an article in New Scientist magazine where the author states that the only way to for the EU and UK to meet their CO2 Reduction Targets is to introduce heat pump technology to heating-cooling refurbishments, both residential and industrial. Since I know a thing or two about heat pumps, I decided to create this web-page in order to pass on some of my knowledge to the less informed. What follows is a very simple description targeted at secondary school students -and- adults with minimal science education.


  1. I have gone out of my way to not mention anything about fossil fuels here.
  2. I will attempt to introduce the non-scientific reader to some scientific terms (kept to the secondary school level)
  3. For simplicity, all explanations here will ignore conversion losses.

Heat Energy, Temperature, and Changes of State

jump: click here if you already know this stuff

Heat Energy and Temperature

Calories and other units

To keep things as simple as possible, the remainder of this article will only use calories


refrigeration cycle


Electric Heat

Air-Source Heat Pumps

Ground-Source Heat Pumps

COP (coefficient of performance)

Other Loops


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Neil Rieck
Waterloo, Ontario, Canada.