They profile a house in Hertfordshire, which is pictured with a roof-full of Solar PV cells and a couple of Solar Thermal banks. The PV array must have cost over £10K, and the hot water panels over £3K. Given this massive investment (which is hopefully producing lots of electricity and hot water), the RHI scheme's return of £89 seems an absolute pittance and probably wasn't worth the time in handling the paperwork.