Comparison Guide

Solar Diverters vs Batteries: Best Value in 2026 (UK)

Both solar diverters and home batteries store the surplus your panels produce — but they do it very differently and at very different prices. In 2026 a solar diverter costs £300–£900 fitted with a 2–4 year payback; a 5–10 kWh battery costs £3,500–£9,500 fitted with an 8–13 year payback. This guide tells you which suits your home, your usage and your tariff.

2026 SEG export rates 4 household scenarios Real payback figures
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Quick Answer

Diverter or battery — which wins in 2026?

The 2026 UK rule of thumb:

  • Diverter wins for: homes with electric immersion water heating, average exports > 1,500 kWh/year, modest usage profile
  • Battery wins for: homes > 4,000 kWh/year electricity use, EV ownership, time-of-use tariffs, gas water heating
  • Both wins for: homes with 5kW+ array, electric heating + EV — fit diverter first, battery within 2 years
  • Diverter payback: 2–4 years (UK average)
  • Battery payback: 8–13 years (UK average) — dropping to 5–7 with smart tariffs
  • Best-of-both 2026 lifetime saving: £12,000–£25,000 over 15 years

Tariff context: SEG export rates in 2026 average 6–18p/kWh; smart tariffs offer 15p+ at peak times. The lower the export rate, the better both options become — because self-consumed energy is worth your full import rate (28–34p/kWh).

Expert Note

Why most installers will quietly steer you toward a battery

Solar batteries carry typical installer margins of £800–£2,000; solar diverters carry margins of £100–£250. The natural commercial outcome is that most solar quotes prioritise battery storage over diverters, and many quotes don't include a diverter at all. This is rarely the right financial answer for the customer.

For a household with electric immersion water heating (the dominant water-heating system in around 18% of UK homes, plus most flats), a £450 diverter that pushes surplus solar into the immersion tank typically saves £220–£380 a year — a 1.5–3 year payback. A 5kWh battery in the same home saves £380–£520 a year for an 8–11 year payback at £4,200 cost. The battery saves more in absolute terms but the diverter wins on return on capital and time-to-payback by a 3:1 margin.

The honest installer answer is: most UK households should fit a diverter first (especially if they have any electric water-heating capacity), then add a battery 2–3 years later when the diverter has paid for itself and battery prices have continued their 8–12% annual fall. The exception is gas-only households with high evening usage — there the diverter has nothing to do, and the battery is the right first investment.

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The Numbers

2026 UK Diverter vs Battery — Side by Side

FactorSolar Diverter5–10 kWh Battery
Installed cost£300–£900£3,500–£9,500
Annual saving£160–£380£380–£920
Typical payback2–4 years8–13 years
Lifetime (years)15–2010–15
Stores energy asHot waterElectricity
Useful in flats?Yes (immersion tank)Yes (wall-mount)
Smart tariff benefitLimitedSubstantial — enables off-peak charging
MaintenanceNoneFirmware updates; capacity drops 2–3%/yr
4 Scenarios

Which One Wins for Your Household?

Diverter wins

Couple, gas central heating, electric immersion backup

3kW solar array, 2,200 kWh exported per year. Diverter (£450) saves £290/year via hot water displacement. Battery would save £340/year but at £4,200 cost. Diverter payback 1.6 years; battery 12+ years. Verdict: diverter.

Battery wins

Family of 4, gas water, EV charging at home

5kW array, 6,000 kWh annual electricity use, off-peak EV charging on Octopus Intelligent Go. Battery (£5,800) saves £850/year via off-peak charging arbitrage + solar self-consumption. Diverter useless (no electric water). Verdict: battery.

Both win

Family of 4, electric water + EV, 6kW array

Diverter handles water heating savings (£320/yr); battery covers evening use and off-peak EV charging (£680/yr). Combined £1,000+/year saving. Total cost £6,500. Combined payback 6.5 years. Verdict: fit both.

Neither yet

Single occupier, 2kW array, gas everything

Small array, low usage, gas hot water. Annual surplus < 800 kWh. Diverter would save £95/year (4.7-year payback); battery 15+ year payback. Verdict: take the SEG export tariff and reassess in 3 years.

2.7yr
Avg diverter payback 2026
10.2yr
Avg battery payback 2026
9p
Avg SEG export rate 2026
31p
Avg import rate 2026
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FAQs

Diverter vs Battery Questions (UK 2026)

A solar diverter (e.g. MyEnergi Eddi, SolarFlow, Solic 200) monitors how much solar electricity you're exporting to the grid in real time and instead diverts that surplus into your immersion-tank water heater. Instead of being paid 6–18p/kWh export, you displace 28–34p/kWh of import — effectively trebling the value of every surplus kWh. It does nothing if you have no electric water heating.
A solar diverter costs £300–£900 fully installed in 2026: £180–£450 for the unit, £120–£450 for an electrician's labour to fit it (typically a 2–3 hour job, NICEIC-registered Part P). MyEnergi Eddi is the most-installed brand at around £380 unit + £220 fitting. Cheaper SolarBoost units are £180 + £150 fitting but lack smart-app monitoring.
A solar battery costs £3,500–£9,500 fully installed in 2026, by capacity. 5kWh systems run £3,500–£5,500; 10kWh systems run £6,500–£9,500; 13–20kWh systems run £9,500–£16,000. Tesla Powerwall 3 (13.5kWh) lists at £9,200 fitted; GivEnergy 9.5kWh runs £6,200; Pylontech US5000 (4.8kWh modular) starts at £2,800 plus £1,800 inverter for first install. 0% VAT applies to retrofits until 2027 — a substantial 20% saving.
2026 UK averages: solar diverter 2–4 years, solar battery 8–13 years. Battery payback drops to 5–7 years if combined with smart time-of-use tariffs (Octopus Intelligent Go, EDF GoElectric) that allow charging from off-peak grid at 7–10p/kWh and discharging at peak 32–38p/kWh. Diverter payback is shorter but absolute lifetime saving is smaller.
Yes — and for households with electric water heating plus high evening electricity use, this is often the optimal setup. The order matters: diverter takes priority when water tank temperature is below set-point; battery takes surplus once water is fully heated; export only happens when both diverter and battery are saturated. MyEnergi Eddi works seamlessly alongside most major batteries (Tesla, GivEnergy, Pylontech). Combined annual savings of £900–£1,200 are realistic on a high-usage 6kW system.
Battery prices have fallen 8–12% per year since 2020 and are expected to continue falling 5–10% per year through 2028. However, electricity prices have risen at similar rates and energy savings compound from year one. The break-even of "buy now vs wait one year" sits at around the 8% annual price drop — below that, waiting loses you a year of savings. The honest answer for most households: buy now if you'll use the battery heavily; wait one cycle if your annual self-consumption uplift would be under £400.
Both qualify for 0% VAT under the energy-saving materials VAT relief, in place until April 2027 (saving £70–£1,900 depending on system). ECO4 grants can include solar batteries for low-income households on means-tested benefits, fully funded for eligible homes. Some local authority schemes (Bristol, Manchester, Bath) offer additional £500–£1,500 contributions. Diverters are rarely covered separately but can be included as part of a wider ECO4 install.
Sources & Further Reading

Our sources for this guide

About This Guide

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Researched, written and fact-checked by the BestBuilders Editorial Team. Cross-referenced against Ofgem, MCS, EST, and our 2026 regional cost model. Reviewed quarterly.

Spotted something out of date? Email info@bestbuilders.co.uk or call 0800 852 7782.

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Written by the BestBuilders Editorial Team. Last updated: 23 August 2026.

Written by the BestBuilders research team from our cost model and published sources. We invite working trades to check our guides – how we check our content · Last updated: 23 August 2026 · See our editorial standards.
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