Geothermal direct use and ground-source heat pumps

Earth heat used directly, or shallow ground heat moved by heat pumps.

Capture · Geothermal · No. 36

• Capture
• Output: Heat and cooling

A ground-source heat pump turns 1 kWh of electricity into about 4.3 kWh of warmth, drawing the rest from soil.

Chart: Illustration: Geothermal direct use and ground-source heat pumps

Where it comes from

Chart: Map of where it comes from

A few metres down, the ground stays at a steady 4.5-21 °C. Pipes in trenches or boreholes 30-120 m deep gather that heat, while deep wells tap hot water directly.

Three things to know

1. In a German field test, heat pumps cut CO₂ emissions by 64% compared with gas heating in 2024.
2. Ground loops last 50 years or more, while the indoor heat pump units last up to about 24 years.
3. Ground-source systems cost several times more than air-source units, but the extra is typically repaid in 5-10 years.

The journey

1. 1 Shallow groundSteady 4.5-21 °C below the surface
2. 2 Ground loopBuried pipes carry water and antifreeze
3. 3 Heat pumpCompressor lifts heat to useful temperature
4. 4 Or hot wellsDeep water feeds heating networks directly
5. 5 BuildingsHomes, greenhouses, fish farms and spas

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