There are always improvements to be made in mechanical devices like heat pumps. This is not a reason to put off the installation of a GHP system, however. Most of the substantial efficiency gains have been made over the past 10 years. Remaining improvements will likely be small in comparison to what has been achieved. As an example, the average performance of five manufacturer's equipment found in the 1987 and current ARI Directories has shown an average of 41% improvement in EER and 27% improvement in COP.
As discussed in the ratings section of this document, the recent changes in the ratings system for water-to-air heat pumps has resulted in a rise in the EER and COP ratings values. In general this is not the result of a general improvement in the equipment itself but rather modifications to the ratings system that improve the numbers.