One of the most common questions we are asked; Is solar thermal a good addition to a ground or air source heat pump system?
The simple answer in most cases is NO. Hot water accounts for 20% of the annual domestic fuel bill. Solar thermal will cover on average 70% of your annual hot water consumption, so really doesn’t provide very much unless you have a very high hot water demand. The RHI pays back around 80% of the installation cost paid back over 7 years. Financially it doesn’t stack up. Plus you have the annual service cost which would be higher than what you would save. With modern high efficiency buildings, solar thermal can be integrated in to a low temperature heating system and cover around 20% of the annual heating load. Unfortunately the RHI does not provide payments to Solar thermal systems & space heating.
In our opinion you are better off in investing in a Solar PV system even though the tariff has been recently been cut. A 4kW PV system can reduce the heat pumps predicted running costs by around 20% plus generate a revenue for 20 years with the FIT. PV still makes sense if you have a heat pump. It would also provide more free hot water than a solar thermal system. Why pay for 2 installations when 1 does it all!
At South West Energy Services we highly recommend Solar thermal systems for indoor and outdoor swimming pools and where there is a higher than average hot water demand (changing rooms or communal showers).