COP stands for Coefficient of Performance. It is a rating used to measure the energy efficiency of swimming pool heat pumps. For example, if you see a COP rating of 6.3, this means that the pool heat pump is consuming 1 unit of electricity while transferring 6.3 units of heat, effectively making the pool heat pump 630% efficient. The higher the COP rating, the more efficient the unit, resulting in lower operating costs. Not all pool heat pumps are created equal – a pool heat pump with a lower COP rating may have a lower sale price, but will cost you more in the long run with higher operating costs.