A solar diverter is a smart device that monitors your home's solar PV export in real time and routes surplus power into a useful load — typically your immersion heater (free hot water) or your EV (free miles). Without a diverter, surplus solar exports to the grid for the SEG (Smart Export Guarantee) rate of typically 5-15p/kWh; with one, you keep the energy at full retail value.
What a diverter does
UK domestic solar PV systems generate more power than the home uses on sunny days — particularly midday in summer. Without a diverter, that surplus exports back to the grid. With a diverter, the device:
- Monitors net export at the consumer unit (via a CT clamp on the supply tail).
- When export goes positive (you're sending power to the grid), the diverter routes the surplus into a chosen load — typically the immersion heater for hot water, or the EV via a paired wallbox.
- Modulates the load proportionally to maintain near-zero export.
Result: every kWh of solar surplus is used in the house at 27-30p/kWh value (avoiding grid imports later) instead of exported at 5-15p/kWh.
The flagship — MyEnergi Eddi
The market-leading UK solar diverter is the MyEnergi Eddi. It diverts to up to two loads — typically the hot water cylinder and a secondary heater. £499 RRP. Built in Stamford, Lincolnshire.
Pairs natively with the MyEnergi Zappi wallbox — together they coordinate, sending solar to the EV first, then to the hot water tank if the car is full or unplugged.
Other diverters in the UK market
- Apollo Gem — single-load diverter for hot water only. Cheaper at £350 RRP.
- iBoost+ Buddy — Marlec's offering, pairs with iBoost wireless sensor. £450 RRP.
- SolarCache — UK-built, supports two loads. £550 RRP.
The Eddi is our default recommendation for UK solar homes — it has the best track record, pairs with the most-installed solar wallbox (Zappi), and has the strongest after-sales support.
When you need a separate diverter
If you're charging an EV and you have solar PV, the question is whether to use a diverter wallbox like Zappi alone, or a Zappi + Eddi combination:
- Zappi alone — diverts solar to the EV when plugged in. Doesn't help when the car is at work or full. Surplus exports to grid in those windows.
- Zappi + Eddi — Zappi diverts to the car when plugged in; Eddi diverts to the hot water tank when the car is gone or full. Captures every kWh of solar surplus year-round.
The Eddi adds £500 + ~£200 install (dedicated wiring to the immersion). Pays back in about 3-5 years through eliminated SEG export and reduced gas heating.
Installation
Diverter install requires:
- A qualified electrician working to BS 7671 18th Edition.
- A CT clamp on the supply tail (or wireless Harvi sensor).
- Dedicated wiring to the diverted load (immersion heater, or signal wire to the wallbox).
- Consumer-unit space for the diverter's MCB.
Most installs complete in 2-3 hours by an installer familiar with UK consumer-unit conventions. Pair with a Zappi install at the same time to save labour cost.
Compatibility notes
Diverters work with any solar PV inverter that exports cleanly — SolarEdge, Enphase, Fronius, GoodWe, Solis, etc. They don't replace the inverter; they add behaviour around it. If you have a solar+battery combination (Tesla Powerwall, GivEnergy), the maths changes — the battery charges first, so the diverter only sees surplus after the battery is full. Worth modelling before buying.
UK SEG rate context
As of 2026, the typical UK SEG export rate is 5-15p/kWh depending on supplier (Octopus Outgoing 15p, EDF 5.6p, OVO Greener Energy 5p). The retail import rate is typically 27-30p/kWh. So every kWh diverted to a useful load is worth 12-25p more than exporting. For a typical 4kW UK solar array generating 3,500 kWh/year with ~30% export, that's £125-220/year of additional value captured by a diverter.