Solar Thermal explained
Solar thermal systems capture the sun's heat to warm water for domestic use — showers, baths, and washing up. They consist of roof-mounted collector panels (flat plate or evacuated tube), a heat transfer fluid, and a hot water cylinder with a solar coil.
How it compares to solar PV:
- Solar thermal converts roughly 60–70% of solar energy into useful heat — more efficient than PV (20%) at the specific task of heating water
- However, it can only produce heat, not electricity — its uses are limited to water (and sometimes space) heating
- Solar PV, combined with a hot water diverter (immersion controller), can achieve similar or better hot water heating results while also generating electricity for all other uses
A solar thermal system (2–4 m² flat plate collectors) typically provides 40–60% of a household's annual hot water needs in the UK, saving roughly £80–£150/year on gas or electric water heating.
Solar thermal has lost popularity in the UK as PV panel costs have fallen. Most installer surveys suggest a solar PV system + immersion diverter (costing ~£200–£350 extra) is now more cost-effective than a dedicated solar thermal system for the majority of households. However, solar thermal remains a viable choice for homes with high hot water demand and limited roof space for PV.