The carbon footprint of a heat pump is dependent on a number of factors including its overall efficiency, whether it is providing space heating and/or hot water, temperature lifts, the refrigerant used, the size of the building, levels of insulation, the hours of operation, and various design, installation and maintenance issues. The EU renewables directive requires that heat pumps must have a minimum Seasonal Performance Factor in order to qualify as a renewable source. The Commission are to issue guidance on how the Seasonal Performance Factor is to be calculated.
An SPF of around 2.7 would make CO2 emissions from gas condensing boilers and heat pumps more or less equivalent with today's grid intensity. At this level of performance the CO2 emissions associated with running a heat pump are considerably lower than those associated with using either oil or electric resistive heating. CO2 savings against all these fuels will improve further, as the electricity grid decarbonises. The Energy Saving Trust field trials are not complete, but, when they are, they will provide useful information on the actual system efficiencies, as well as information to improve installation and maintenance practice.