Solar + EV: How to Charge for Almost Free (UK 2026)

Solar EV charging in the UK has moved from a niche enthusiast setup to a practical mainstream choice in 2026 — driven by falling solar PV costs, a stable Smart Export Guarantee scheme, and the Zappi-style chargers that divert surplus PV straight into the EV. Get the sizing right and a typical 10,000-mile-a-year driver can run their car for under £50 a year. This guide covers the maths, the kit, and the setup that actually pays back.

A 5-6 kWp solar array in the UK generates roughly 4,500-5,500 kWh a year. An EV doing 10,000 miles at 4 mi/kWh needs about 2,500 kWh of grid-input charging annually. If even half of your generation lands inside the charging window, you've covered most of the car's annual energy from sunlight. The leftover 30-50% is bought at Intelligent Octopus Go's off-peak rate (around 5.49p/kWh in most regions from 1 April 2026), and any solar surplus you don't self-consume is exported to the grid at 12p/kWh via Outgoing Octopus. The net result for many UK households is an EV running cost in the £20-£60/year range — effectively free motoring once the panels are paid off.

A standard 7 kW home charger draws a constant 7 kW from the grid for the whole session. A solar array on a UK roof in May might be generating anywhere from 1 kW to 5 kW depending on the cloud cover that minute. The mismatch matters: if you simply turn on a 7 kW charger when the sun is up, you'll pull most of the 7 kW from the grid and waste the solar generation on bill offset.

A solar-diverting charger fixes that mismatch in real time. The myenergi Zappi is the best-known example — in Eco+ mode, it reads the live PV generation and household consumption (via a CT clamp or wireless Harvi sensor), then modulates the EV charge between 1.4 kW and 7.4 kW to match only the genuine solar surplus, with zero grid draw. When a cloud passes and surplus falls below the minimum, the charger pauses entirely; when the sun returns, it ramps back up automatically.

Andersen, Indra and Hypervolt also offer solar-diverting modes via integrations with home battery systems or PV inverter APIs. The Tesla Wall Connector pairs with Powerwall for similar behaviour. See our UK home EV charger comparison for the full list with solar feature parity.

This is the question that determines whether the solar+EV system actually pays back. The instinctive answer is "charge from solar whenever the sun is shining" — but with Intelligent Octopus Go's off-peak rate now near 5.49p/kWh and Outgoing Octopus paying 12p/kWh for exported surplus, the maths is more nuanced.

The first option (direct solar) is worth ~12p/kWh in displaced grid imports; the second option (export then re-import at off-peak) is worth ~6.51p/kWh. Direct solar wins on a per-kWh basis. The catch is that direct solar requires the EV to be parked at home during the generation window — for office commuters, the car is at work between 9 am and 5 pm, when generation is highest. For those households, exporting and re-importing overnight is actually the higher-value path for the kWh that would otherwise have been wasted.

The 2026 best-practice setup for a UK home that already plans to run an EV looks like this:

The sizing is deliberately conservative on PV (5-6 kWp rather than maxing the roof to 8-10 kWp) because once you've covered annual EV charging plus typical household usage, marginal kWh of generation only earn 12p/kWh on export — they don't displace anything more expensive. Larger arrays only make sense if you'll also be running a heat pump or have a second EV.

A home battery makes economic sense when there's a structural mismatch between when the panels generate and when the household uses energy. Three scenarios where it pays back well:

Skip the battery (or run a smaller one) in these cases:

Assumptions: Reading-area south-facing 5 kWp array generating 4,800 kWh/year. EV doing 10,000 miles at 4 mi/kWh = 2,500 kWh needed. Household baseline usage (excluding EV) 3,000 kWh/year. Adult working from home 2-3 days/week — EV at home roughly half of generation hours.

Against an installed cost of roughly £11,000-£12,000 for the solar + battery + charger combination, the £1,170/year benefit gives a payback period of 9-10 years before any inflation adjustment on grid electricity. With the EV's annual fuel cost effectively dropping from £1,200+ (a 35-mpg petrol car at 140p/litre over 10,000 miles) to £60, the comparison-to-petrol payback is closer to 7 years.

A few setup details that commonly trip up first-time solar-plus-EV households:

The Smart Export Guarantee (SEG) is the regulatory framework that requires UK electricity suppliers with 150,000+ domestic customers to offer some form of export tariff to small-scale solar generators. Each supplier sets its own rate. Octopus Outgoing has been the most-used because of its simplicity (flat rate, no time-of-use complexity) and competitive pricing.

On 1 March 2026 Octopus cut the Outgoing rate from 15p/kWh to 12p/kWh — the first change since the 2022 increases. The headline rate is still competitive against most rival SEG offerings, but the gap has narrowed. Customers locking in long-term should run their payback maths at 12p, not the historical 15p that older guides still reference.

Note that Outgoing Octopus is opt-in and requires a SMETS2 smart meter operating in HH (half-hourly) mode and an MCS certificate from the install. Without HH metering, suppliers default to the lower SEG export band.