What is a solar diverter (for hot water)?
A solar diverter is a small device that sends your surplus solar electricity to your immersion heater, heating your hot water for free instead of exporting it at the lower SEG rate. It costs around £200 to £400 fitted and suits homes with a hot water cylinder, effectively giving you some of the benefit of solar thermal from a PV system.
How a diverter helps
- Surplus solar heats your water instead of exporting at ~15p per kWh.
- You avoid paying to heat that water by gas or off-peak electricity.
- It only diverts genuine surplus, so it never increases your import.
- Best for homes with a hot water cylinder rather than a combi boiler.
Is it worth fitting?
If you have a cylinder and reasonable solar surplus, a diverter often pays for itself within a few years by replacing water-heating costs. If you have a battery, the two compete for surplus, so your installer can advise on the best balance for your home.
Frequently asked questions
- Does a solar diverter work with a combi boiler?
- No, it needs a hot water cylinder with an immersion heater. Combi-boiler homes cannot use a standard diverter.
- Diverter or battery first?
- A diverter is cheaper and great for hot water; a battery is more flexible. Some homes use both, prioritising as their installer advises.
Related questions
Indicative estimates based on UK average data. Last updated 27 May 2026.