When air source heat pumps and air conditioners are rated they are rated with a SEER number. SEER is Seasonally adjusted Energy Efficiency Ratio. This represents the average efficiency of the unit over one 'season'. But, who will actually get this SEER from the unit? People in Miami, Florida or people in International Falls, Minnesota? The problem with the SEER is that it is not the true number for most homes. SEER ratings are ONLY good for comparing equipment that use SEER ratings, and it doesn't have much value otherwise.
The efficiency of a geothermal heat pump (EER: energy efficiency ratio and COP: coefficient of performance) is rated at specific entering water and air temperatures to the unit. So, if you are to compare apples to apples you will need to compare the EER and the COP of each geothermal heat pump calculated at the same rating conditions. However, geothermal heat pumps are so much more efficient than any other type of heating or cooling equipment, that any geothermal heat pump (properly sized and properly installed) will save you a tremendous amount of money.