Solar Diverter Cost Calculator
A diverter sends surplus generation to your immersion heater instead of exporting it. Cheap to fit, and it pays back faster than almost anything else you can add to a solar system.
Open the calculator →Price a diverter in 30 seconds
3 steps. Covers the device, the electrical work, and whether you need a cylinder or immersion added.
How this calculator works
A diverter watches your export and, instead of sending surplus to the grid for a few pence, pushes it into the immersion heater in your hot water cylinder. The economics are simple: exported units earn you the SEG rate, whereas the gas or electricity you would otherwise burn to heat that water costs considerably more. You capture the difference.
The device is the smaller part of the cost — most of it is the electrician’s time and the cable run from the consumer unit to the cylinder. That is why the install question moves the number more than the choice of unit does. And the hard constraint: no cylinder, no diverter. If you are combi-only there is nowhere to put the heat, and a battery is the product to look at instead.
Solar diverter costs (2026)
| Item | Typical 2026 cost | Notes |
|---|---|---|
| Solic 200 | £260–£330 | Simplest, no app or metering |
| Marlec Solar iBoost+ | £300–£380 | Wireless sender, boost function |
| myenergi Eddi | £475–£575 | App control, metering, pairs with Zappi |
| Installation, short run | £150–£220 | Cylinder near the consumer unit |
| Installation, standard run | £250–£380 | The usual case |
| Immersion element, if missing | £180–£280 | Element plus thermostat |
Device prices match our solar diverter guide. A diverter only makes sense where you have a hot water cylinder — there is nothing for it to heat in a combi-only home.
Solar diverter calculator FAQs
Typically £120–£220 a year for a household with a cylinder and reasonable daytime surplus. The saving is the gap between what an exported unit earns you under SEG and what it costs to heat that water by gas or standard-rate electricity. Payback is usually three to five years.
A diverter if you have a cylinder and your surplus is modest: it costs a fraction of a battery and pays back faster. A battery if you have no cylinder, a large surplus, or you want to shift cheap-rate import overnight. They are not mutually exclusive, and a diverter is often the sensible first step.
No. A combi heats water on demand with no storage, so there is nothing for the diverter to heat. If you have no cylinder, your options for using surplus are a battery or an EV charger that responds to generation.
Yes, and that is the point. Most SEG tariffs are paid on deemed or metered export, so anything you divert is no longer exported. You are trading a few pence per exported unit for the larger sum you would have spent heating that water another way.
Related cost guides
- Solar diverter guide — how it works and what to specify
- Diverter vs battery — which is worth doing first
- Solar battery calculator — price storage instead
- Solar panel costs — system prices, export rates and payback
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