Geothermal energy uses a high-temperature heat source powered by underground natural nuclear reactions, and passive heat exchangers.

Ground-source heat pumps use ambient ground temperatures, which tend to be about the same as annual average air temperature. The ground's heat is recharged each summer by the sun. The heat is extracted using active technology, compressing and expanding fluids to lift the temperatures to something useful.

A ground-source heat pump is not a form of geothermal energy at all.

Geothermal:

1. energy source is underground natural nuclear reactions;
2. source temperature is over 50°C;
3. Energy is extracted with passive heat exchangers.

Ground-source heat pumps:

1. energy source is solar radiation;
2. source temperature is about the same as annual average air temperature;
3. Energy is extracted using active technology, compressing and expanding fluids to lift the temperatures to something useful.