What is air conditioning?

Air conditioning units are heat pumps, and generally provide heating as well as cooling. Air conditioning uses an air-to-air heat pump, meaning that heating or cooling energy is transferred directly to the air. Air, ground and water heat pumps transfer the heating or cooling energy to water and then to underfloor, radiators, etc.

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The performance of the air conditioning unit is provided by the "Coefficient of Performance" (CoP) and "Seasonal Coefficient of Performance" (SCoP). The CoP is the instantaneous efficiency and the SCoP is the CoP averaged out over the year. The SCoP is the most relevant to determining how a system will perform. A unit with a SCoP of 4 provides 4kW of heat for 1kW of energy used.

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Air conditioning provides an alternative to conventional heating systems and is potentially the cheapest way of heating a property when using electricity. Mitsubishi have published that the MSZ-LN Premium R32 units have a SCoP of between 4.6 and 5.2. This means that an air conditioning system will cost less to run than most other forms of heating. If heating is provided by air conditioning, a separate method is required to heat hot water – e.g. a self-contained hot water heat pump tank, which can achieve a SCoP of >3.19.

With the recent volatility in energy prices, it is difficult to provide a consistent analysis of how the various sources of energy for heating compare. The Nottingham Energy Partnership website provides monthly comparisons of energy cost. 

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Based on information from July 2022, the cost of heating/cooling in order of least cost: