Solar Power Diverter
Send your surplus solar to the hot water tank instead of exporting it for pennies. myenergi Eddi and Marlec Solar iBoost, fitted across Norfolk and Suffolk.
Use the solar you're giving away.
On a sunny day most solar systems generate more than the house is using, and that surplus gets exported to the grid for a low rate. A solar power diverter - also called a solar immersion diverter or PV diverter - spots that surplus and quietly sends it to your immersion heater instead, heating a tank of hot water for free rather than paying for gas or a timed immersion later. It's one of the cheapest ways to get more value out of an existing array. Wave Renewables supplies and fits them with the same fixed-price approach as every other job.
- Cuts the cost of heating hot water with gas or peak electricity
- Simple, low-maintenance - a small box near your consumer unit
- Retrofits to existing solar, any installer
- Works alongside a battery and an EV charger
Surplus in, hot water out.
The diverter sits between your immersion heater switch and the immersion element, and monitors the electricity flowing in and out of your home at the meter. The moment you're exporting - generating more than you're using - it feeds that exact amount into the immersion element, ramping up and down second by second so nothing goes to the grid until the tank is hot. When there's no surplus, the immersion behaves normally as a backup. Smarter units like the myenergi Eddi can prioritise between hot water, a second heater and other myenergi kit such as the Zappi EV charger.
Which diverter.
Marlec Solar iBoost
The long-standing UK favourite. Wireless clamp sensor, simple to fit, does one job well - heating your cylinder. Around £250-£300 for the unit.
myenergi Eddi
Made in the UK. Two heater outputs, app monitoring, and talks to other myenergi devices so hot water, battery and EV charging share the surplus sensibly. Around £400 for the unit.
SolarEdge / inverter-integrated
If you have a SolarEdge system, a matched diverter can be driven straight from the inverter with no extra sensing. We'll say if yours supports it.
Not sure it's for you?
No cylinder or a combi boiler means a diverter has nothing to heat. In that case a battery is the way to hold on to surplus solar.
Depends on your export rate.
If you're on the old feed-in tariff, a diverter is close to a no-brainer - the FIT pays you the same whether you export or not, so any surplus you use at home is a straight saving. On the Smart Export Guarantee it's a judgement call: if your export rate is high, the grid may pay you more for that surplus than you'd save on hot water; if it's low (under about 12p/kWh) and you use a lot of hot water, the diverter wins. A diverter typically pays back in a few years and the units last around 10 years. We'll look at your tariff and usage and tell you straight whether it's worth doing.
Solar diverter FAQs.
A small electronic device that watches your solar generation and, when you're producing more than the house is using, sends that surplus to your immersion heater to warm the hot water cylinder instead of exporting it. Also called a solar immersion diverter or PV diverter.
The unit is roughly £250-£300 for a Marlec Solar iBoost and around £400 for a myenergi Eddi, plus fitting. We give a fixed installed price for your setup before any work starts.
No. A diverter heats water in a stored hot water cylinder via its immersion element. With a combi boiler and no cylinder there's nothing for it to heat.
It depends on your export rate. A high Smart Export Guarantee rate can be worth more than the hot water you'd save; a low rate plus high hot water use means a diverter usually pays for itself within a few years.
A battery stores surplus for any use later and saves more overall, but costs several times as much. A diverter only heats water but is cheap and simple. If hot water is a big part of your bill and budget is tight, a diverter is a sensible first step.
Yes - we add diverters to existing systems across Norfolk and Suffolk regardless of who installed the panels.
Unit prices are indicative, from manufacturer and UK retailer guide pricing for the Marlec Solar iBoost and myenergi Eddi (September 2026). We quote a fixed installed price.
Last reviewed September 2026.
Stop exporting it for pennies.
Get in touch for a free, no-pressure quote on a solar diverter.