Predicted v Actual Performance: Average gas consumption before the heat pump was installed was 14,906 kWh per annum. Predicted electricity consumption for the ASHP was 3,911 kWh per annum. Actual electricity consumption over the first year was 3,394 kWh.
Cost of Running: Annual electricity costs for the ASHP were £1,246 compared to £1,718 gas heating costs. Costs are based on the 1st October 2022 – 30th June 2023 Energy Price Guarantee tariffs (36.7 p/kWh for electricity and 10.9 p/kWh for gas) and account for the saving on gas standing charge.
ASHP Case Study No. 2
Property Type: 1980s, 6-bed detached, 280 m2 floor area, timber framed with cavity wall extensions. Previously heated by an oil boiler. A wood-burning stove was retained. Property already had double glazing and 300 mm loft insulation.
Predicted Performance: Seasonal Performance Factor of 3.8 predicted, excluding hot water. An annual fuel bill saving of £199 (at 2021 energy prices) was projected.
Actual Performance: Seasonal Performance Factor of 3.2 achieved, excluding hot water and 2.9 including hot water. At 2021 energy prices this gives a £15 increase in annual energy bills. At current electricity prices (30.1 p/kWh) and average oil prices over the past 12 months, this gives a £43 saving on annual energy bills. So bill impact is broadly neutral.