The Microgeneration Certification Scheme (MCS) has published a new solar thermal calculation method ahead of the introduction of the domestic Renewable Heat Incentive (RHI) next year.

The new calculation is an improved version of the existing Standard Assessment Procedure (SAP) method. One of the major changes introduced by the new method is the removal on one irradiation figure for the whole of the UK and the implementation of regional bands. In addition, the effect of the efficiency of the back-up heater (usually a boiler) is recognised, increasing the annual energy saving presented to the customer by at least 30%.

The Solar Trade Association (STA) believes that the revised method will increase the level of deemed renewable heat by between 14% for a two person household and 85% for a six person household. As the method will be used as the basis for domestic RHI payments, the impact on potential payments should be significant.

“We welcome the improvements to the energy calculation,” said Paul Barwell, chief executive of the STA. “Since the announcement of the domestic RHI tariffs in June, the industry has been waiting for clarity on this point. At last, solar installers can put the benefits of solar heating under the domestic RHI in front of potential customers.”

Stuart Elmes, chair of the solar thermal working group at the STA and a contributor to the development of the new standards added: “Solar installers who took a look at the tariff of 19.2p per kWh and decided that the domestic RHI wasn’t all that good, should look again at the numbers. The new calculation makes a big difference. We are also doing some work around the financial benefits of the hot water cylinder upgrade which we intend to reveal shortly.”

The STA is hosting a free Solar Thermal Seminar at Solar Energy UK on Tuesday 8th October 10.45-13.00 at the NEC where delegates will hear about the new energy calculation, the domestic RHI and the impact on solar thermal return on investment.