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.
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.
Battery interaction
With a battery, set priorities so the diverter only takes leftover surplus after the battery is charging — most units support this ordering.
Common Questions
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