## RHI Legacy applicant assumes low SPF

We had an interesting question from one of our readers last week regarding legacy RHI claims.

It is assumed that any heat pump installed before the 9th April 2015 (known as a legacy install) will have a seasonal performance factor (SPF) of just 2.5.

Seasonal performance factor refers to the efficiency of the heat pump that is installed. For example, a seasonal performance factor of 2.5 means that for every 1 unit of electricity required to run the pump, you get 2.5 units of useful heat in the home.

If you compare that to a standard electric heater, you can see why heat pumps are so efficient. A standard electric heater, despite being 100% efficient will have an S.P.F of 1, so each unit of electricity produces just one unit of heat.

Now, an SPF of 2.5 doesn’t really sound too bad, but actually for new heat pumps the rate should be nearer 4.5 and it makes a considerable difference to the RHI payments.

The Government give you the choice of whether to accept the legacy RHI application where it assumes an SPF of 2.5 or get the MCS accredited heat pump installers to do calculations to determine the specific SPF of the system. So our reader’s question related to whether it was worth getting her system reassessed or whether to accept the SPF of 2.5 for her legacy RHI install.

So lets run the numbers to show you the difference purely based on the SPF rating – the heat demand of her property was 28,532kWh (from the bottom of her EPC) and she installed a GSHP.

## RHI payments with Legacy SPF of 2.5

The formula for calculating the yearly RHI payment is as follows

28,532 x ( 1 – 1 / 2.5 ) = 17,119 kWh of eligible heat under the RHI scheme

Multiply this by the tariff for a Ground source heat pump

17,119 x 18.8p / kWh = £3218 annually, guaranteed for 7 years.

£3,218 x 7 = £22,529 total payment

## RHI payments with SPF of 4.5 after reassessment by installer

The formula for calculating the yearly RHI payment is as follows

28,532 x ( 1 – 1 / 4.5 ) = 22,191 kWh of eligible heat under the RHI scheme

Multiply this by the tariff for a Ground source heat pump

22,191 x 18.8p / kWh = £4,172 annually, guaranteed for 7 years.

£4,172 x 7 = £29,204 total payment

## <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}-->Is it worth getting your legacy heat pump install reassessed?

In a word yes, especially if you have had a ground source heat pump installed where the SPF should be considerably higher. With an air source heat pump, you might not see quite the increase in payments, mainly because the SPF tends to be lower anyway (around 3- 3.5) but even so it should still see you receive larger payments.

### >>> Learn the differences between GSHP and ASHP <<<

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