How to Plan a Solar Diverter Installation (2026 UK)
A solar diverter (also called an immersion or power diverter) takes the surplus solar PV electricity you would otherwise export to the grid for a few pence and sends it to your hot-water immersion heater instead — turning free midday sunshine into a tank of hot water. Most are fitted for £200–£600 and pay back within a few years. Success comes down to two checks: do you have a compatible hot-water cylinder with an immersion element, and do you regularly export surplus solar? Follow the seven steps below.
Solar diverter installation — the short answer
- What it does: diverts surplus solar PV to your immersion heater instead of exporting it cheaply.
- You need: a hot-water cylinder with an immersion element and regular daytime solar surplus.
- Typical cost: £200–£600 fitted for the unit and an electrician's half-day.
- Payback: often 2–4 years through reduced gas/electric water heating.
- Must be installed by: a qualified electrician — it taps into your consumer unit and tank wiring.
If you have a combi boiler and no hot-water cylinder, a standard immersion diverter has nothing to heat — you would need a different approach such as a heat-battery or battery storage. So the very first thing to confirm is that you have a vented or unvented cylinder with a working immersion element. For the bigger picture on returns, read whether a solar diverter is worth it for hot water.
The 7-Step Plan
Work through these in order — each step confirms the diverter will actually save you money before you commit.
If you also have a home battery, decide your priority: charging the battery usually beats heating water on value, so set the diverter to take only the genuine leftover surplus.
What Makes or Breaks a Solar Diverter
Do you have a cylinder?
A diverter needs an immersion heater in a hot-water tank to push surplus into. Combi-boiler homes with no cylinder cannot use a standard immersion diverter.
Size of your surplus
The bigger and more regular your daytime export, the faster the payback. A 4kW+ array that often exports at midday is the ideal candidate.
Export tariff vs saving
If you are on a generous Smart Export Guarantee rate, weigh the export income you give up against the gas or electric water heating you avoid. Our guide to solar export tariffs shows which pay most.
Battery interaction
With a battery, set priorities so the diverter only takes leftover surplus after the battery is charging — most units support this ordering. If you are weighing the two, see our comparison of a solar diverter vs a battery.
Common Questions
Related Guides
More how-to, cost and compare guides for your solar and home-energy project.
Get 3 Free Solar Diverter Quotes
BestBuilders matches you with up to 3 local solar and electrical installers who price your diverter installation against one brief, so you compare like-for-like. It is free with no obligation, and you choose who to hire.