Answer by Dale Blundell (Atkins)
Heat pumps are sometimes considered renewable because they use (renewable) heat from the environment to provide heat for space heating/cooling and water heating. While it is true that the source of heat energy is free and in most cases limitless, an electrically driven pump is needed to drive the compressor and circulate the working fluid. The claim for a heat pump being truly renewable is therefore only valid when the electricity used to drive the pump comes from a non-fossil fuel source. Indeed, as the grid de-carbonises by moving from fossil fuels to truly renewable energy sources, this will become increasingly the case. Heat pumps are usually more accurately described as a “low carbon technology”, rather than a renewable source of energy.
The actual carbon emissions from a heat pump, and alternative sources of heat, can be calculated by comparing carbon intensities of the different fuels and system efficiencies.
For an ASHP of SPF = 2.7, and an EU average electricity carbon intensity of 0.4kgCO2/kWh, it will have a net value for the heat delivered of 0.148kgCO2/kWh.
For a GSHP of SPF = 3.4, the net value of carbon intensity for the heat delivered of 0.117kgCO2/kWh.
By comparison, when considering a natural gas boiler of 90% efficiency, and a carbon intensity for natural gas of 0.185 kgCO2/kWh, results in a net value of 0.206kgCO2/kWh for delivered heat.
CO2 emissions for heat pumps will improve with increasing decarbonisation of the electricity system and increasing COP factors. There is not much scope for improvement for emission factors related to natural gas.