Payments Explained & Examples

Seasonal efficiency of heat pumps is called “Seasonal Performance Factor” (SPF), which takes into account the heat loss from the building, overall efficiency of three main components of the heating system; heat pump, the temperature of the water running through the radiators and heat pump, size of the room emitter; either radiators, fan coil units or underfloor heating. The secret is a low flow temperature, increasing the efficiency of the heat pump, giving a higher SPF and lower running costs, but to achieve a lower flow temperature; either the heat emitters will need to be sized accordingly; in most cases they will have to enlarged to give a larger emitter area to maintain the heat loss of the living area, or the fabric and ventilation needs to be improved. This factor is calculated by the MCS installer using “The Heat Emitter Guide”. A PDF of this guide is available below.

The SPF relates to how much heat the system generates per unit of electricity it uses – for example, a heat pump with an SPF of 3; generates three kWh of heat for every kWh of electricity it uses. The eligible heat for the purposes of RHI payment will be worked out using the following formula:

Eligible heat demand = Total heat demand x (1 – 1/SPF), this means that if the heat pump has an SPF of 3, two-thirds of the heat output will be renewable and therefore eligible for RHI payments.


Typical 3 Bed house
Actual Energy usage19412 kWh pa
EPC Rating17489 kWh pa
Calculation1-1/SPF 0.63
RHI Annual Payment£803.85

Gasolder (non-condensing) £/year £395 to £590 – £2,325 to £3,690 – Carbon dioxide/year 1.8 to 2.9 tonnes
Electric (old storage heaters) £/year £650 to £1,215 – £2,325 to £3,690 – Carbon dioxide/year 6.2 to 11.1 tonnes
Oilolder (non-condensing) £/year £650 to £1,035 – £2,325 to £3,690 – Carbon dioxide/year 2.6 to 4.2 tonnes
LPGolder (non-condensing) £/year £1,265 to £2,000 – £2,325 to £3,690 – Carbon dioxide/year 2.5 to 4.0 tonnes
Coal £/year £575 to £990 – £2,325 to £3,690 – Carbon dioxide/year 6.8 to 11.1 tonnes

Call us today on 01344 356900 for more information and to find out how much you can save on your annual heating bill.