ASHP Case Study No. 1

Property Type:

1940s, 3-bed semi, 128 m2 floor area. Previously heated by a gas combi boiler. Owner had already topped up loft insulation to 350 mm, installed cavity wall insulation, solar PV and a battery storage system.

Heat Pump Installation:

Mitsubishi Ecodan Ultra Quiet 11.2 kW ASHP, hot water tank in utility room, 9 new radiators (most rooms), 45 degrees C flow temperature, £13,000 cost (without any grant).​

Owner Experience:

​Installation times: “It might take longer than you expect to get a quote, to do the design work. Don’t wait until your heating system has died, you can’t do it in a hurry”. ​

Warmth: “You can’t tell the difference…the house is just as warm as it was before”. ​

Noise: “It does make a noise, but you don’t really hear it from inside and it’s not very loud.”.​

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.

Heat pump installation: Daikin Altherma 16 kW ASHP, separate external and internal (including hot water cylinder) units, some new radiators. Operates at 35-45 degrees C flow temperature (weather compensated). Installation cost £13,600 in 2021 (without any grant, installed under the Renewable Heat Incentive (RHI) scheme).

Owner Experience:

How did you finding an installer?: “With difficulty! All very busy with new builds and the RHI scheme ending in March 2022.”

Installation times: “Less than 2 months from initial quote to installation. The installation took a week.”

Any installation challenges?: “The boiler was not located in a room with an outside wall, so the pipe run was more complex”

Noise: “Very quiet. Indoor unit has a pump similar to any oil/gas boiler. Outdoor unit fans run quietly even under the coldest conditions”.