Solar PV vs Solar Thermal — UK Compared

For most UK homes in 2026, solar PV offers better value. A 4kWp PV system costs £5,000-7,000 and generates electricity worth £400-700/year (self-consumption plus Smart Export Guarantee). Solar thermal costs £3,000-5,000 but only offsets hot water costs of £150-300/year. PV is more versatile since electricity can power anything including an immersion heater.

A typical 4kWp solar PV system needs about 20 m² (10 panels at 2 m² each). A solar thermal system for a 3-bed house needs just 3-5 m² for flat plates or 2-3 m² for evacuated tubes. Solar thermal is far more space-efficient per kWh of hot water produced, but solar PV can use a larger roof area productively.

Yes, and some homes benefit from the combination. Solar thermal provides highly efficient hot water heating on a small roof area, leaving remaining space for PV panels. However, with PV prices falling and heat pump diverters available, many installers now recommend PV with a power diverter (like an iBoost) to heat water with surplus electricity instead of installing separate thermal panels.

Solar PV typically pays back in 7-10 years in the UK, depending on self-consumption rate and electricity prices. Solar thermal pays back in 10-15 years. Both systems have 20-25 year lifespans, so both deliver positive returns, but PV delivers the better financial outcome in most scenarios.

Solar thermal panels produce significantly less hot water in winter — typically 10-20% of summer output. Evacuated tube collectors perform better than flat plates in low light conditions. Most UK solar thermal systems need a backup boiler or immersion heater from October to March. They still provide useful pre-heating that reduces boiler runtime.