If you’ve been waiting to find out exactly how much you will receive in RHI payments before going ahead with a solar thermal installation, the government has released its ‘calculation methodology’ – and it’s good news.

Based on an average house, if you were to have a solar thermal system installed, Viridian Solar has worked out that energy savings will be between 50% and 142% higher than they would have been if the old calculation had been used, and the deemed renewable heat will be between 14% and 85% higher. That’s some serious improvements!  And with higher solar radiation levels in the south west than anywhere else in the country, the financial incentives are even greater.

So, what’s changed?  Well, the previous calculations used the government’s ‘standard assessment procedure’ (SAP) for many things, including basing household occupancy on the floor area of a house.  The new calculation is much fairer, however, using the actual number of occupants in a house.

The new calculations also:

  • require the installer to enter whether or not the property has an electric shower
  • include the heater’s backup efficiency
  • include cylinder standing losses
  • allow use of a property’s exact location

All in all this means that, under the RHI, solar thermal makes even better financial sense than we first thought (particularly as you can still get up to a £600 upfront grant towards the installation).