Energy efficiency is typically calculated from the amount energy delivered divided by the energy supplied to do that work. With heat pumps energy efficiency is calculated two different ways.
Heating Efficiency is expressed as a Coefficient of Performance (COP). The higher the COP, the more efficient the system is.
A geothermal heat pump that has a COP of 3.4 or higher. This means that for every one 1 unit used to power the system, 3.4 units of energy is created to heat your home. A 92% efficient furnance requires 1 unit of energy for only .92 units of energy produced to heat your home.
Cooling Efficiency is measured as Energy Efficiency Ration (EER). The higher the EER, the more efficient the cooling equipment is. The EER is a ratio of the cooling output in BTU divided by the power consumption in watts per hour.
A geothermal heat pump typically has an EER rating between 13 and 18, depending on the models and cooling configuration of your home.