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Air Source Heat Pump Case Study

Mr Jones had an oil boiler which was installed over 10 years ago, and he was paying 50p per litre for his oil. He had Greenscape replace the boiler with an 11.2kW Ecodan heat pump, and pays 14p per unit of electricity.

  • 11.2kW heat pump
  • All double panel radiators (no underfloor heating)
  • SCOP of heat pump based on the two bullet points above the following heat demand figures on his EPC
  • The heat demand figures on his EPC are below:




RHI Calculations

You are paid for every renewable unit used to heat your property – based on its heat demand (space heating + water heating) which can be found on your Energy Performance Certificate (EPC). (The RHI is capped at 20,000kWh of heat demand).

Electricity Used to Run Heat Pump
Heat demand, divided by the heat pump efficiency (also referred to as the SCOP), gives you the amount, in units of electricity that you use to power the heat pump.

Mr Smith’s 11.2kW Ecodan unit, running the flow temperature at 45 degrees, will have a SCOP of 3.52

20,000 / 3.52 = 5,681kWh

Renewable Units of Heat Produced
If you take the electricity used away from the total heat demand, you are left with the amount of renewable units of heat that your heat pump will produce to heat your home.

20,000kWh – 5,681kWh = 14,319kWh


Annual Combined Earnings

Annual RHI Payment
The renewable units of heat times by the RHI rate (10.18p/kWh) gives you the annual RHI payment.

14,319kWh x 10.18p = £1,457.67


By including the metering package on his system, he will earn an additional £1,610 over 7 years.

So the annual payment works out as:



Annual Combined Savings

An oil boiler which is over 10 years old is estimated to have a fuel efficiency of 75%, whereas the heat pump (at a 45 degree flow temperature), will have an efficiency of 352%.

The cost per kWh of his oil works out at 7.6 p per unit.
The heat pump will run at 4p per unit.

This represents a 52% saving on his heating bills.

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