Is It Cheaper to Charge Your EV From Solar or Export It? (UK, 2026)

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The Short Answer

When your solar panels produce more than the house is using, you have two choices for the surplus: send it into your EV, or export it to the grid for cash. Almost everyone assumes using it yourself is obviously better. For general household load, it is. For EV charging in the UK in 2026, it often isn't — because your car is the one big load you can move to the middle of the night, where electricity is astonishingly cheap.

Here is the whole article in one line:

Export your solar if your export rate is higher than your cheap overnight charging rate. Otherwise, charge the car directly from the panels.

Everything below is why that rule is true, and what the numbers look like today.

Why "Always Self-Consume" Used to Be the Right Answer

Every unit of solar you use yourself is a unit you don't buy from the grid. The value of self-consumption is therefore the import price you avoid — and UK daytime electricity runs around 24–28p/kWh.

For years, exporting paid almost nothing: the legacy Smart Export Guarantee rates from most suppliers were 4–5p/kWh. Avoiding a 25p import beats earning 5p every time, so the advice was simple and correct: use every kWh you can, export only the leftovers.

For your fridge, lights, heat pump, and everything else that runs during the day, this is still true. Those loads happen when they happen, at the full daytime rate, so covering them with your own solar is worth ~24–28p/kWh. Nothing in this article changes that. This is only about the car.

The One Assumption That Breaks for an EV

The reason the car is different: you can decide when it charges. It doesn't need the energy at 1pm when the sun is out — it needs a full battery by morning. And overnight, the UK has some of the cheapest domestic electricity in Europe.

On a smart EV tariff like Intelligent Octopus Go, the overnight rate is around 7p/kWh (roughly 23:30–05:30). So the real alternative to charging your car from solar isn't paying 25p — it's paying 7p to fill it overnight from the grid instead.

That completely changes the comparison. You are no longer weighing "free solar" against a 25p bill. You are weighing what your solar earns as export against what the same energy costs you overnight.

The Decision, in One Line of Arithmetic

Take a single surplus kWh at midday. You need to get one kWh into the car by tomorrow morning either way, so hold the car's energy need fixed and just follow the cash:

Option A — Self-consume (solar → car now):

• Solar charges the car: no grid cost, but you earn nothing from export.
• Net: £0.

Option B — Export now, charge the car overnight:

• Export the solar kWh: earn your export rate.
• Refill that kWh into the car overnight: pay your overnight rate.
• Net: export rate − overnight rate.

So the comparison collapses to one number:

Export advantage per kWh = export rate − overnight import rate.

Positive → export the solar. Negative → charge the car directly.

That's it. No solar-production model, no seasonal curve — those decide how much surplus you have, not what to do with it. This one subtraction, using today's rates, decides direction.

The pivot is clear: if you're stuck on a 4–5p export rate, keep self-consuming. If you've moved to any of the competitive 15–25p export tariffs — and paired it with a cheap overnight EV tariff — exporting the solar and charging the car overnight is the cheaper route.

Current UK Rates — Verified July 2026

Import and export contracts in the UK are decoupled — you can take a cheap overnight import tariff from one setup and a high export tariff separately — which is exactly what makes the arbitrage above possible.

⚠️ Tariffs move fast. These figures were verified in July 2026 and are here to show the shape of the decision, not as a live price list. The rule in this article — compare your export rate to your overnight rate — stays correct whatever the numbers do. Always check your own current tariffs before acting. Note: Intelligent Octopus Flux (which paid up to ~32p at peak) has been closed to new customers since April 2026.

Worked Example: 12,000 Miles a Year in Manchester

EV: Volkswagen ID.4 Pro · Mileage: 12,000 mi/yr · Solar: 8 × 400W, south-facing. Of the car's ~4,060 kWh annual appetite, solar realistically overlaps with about 1,800 kWh of daytime charging opportunity.

What to do with that 1,800 kWh of car-bound surplus:

So on Octopus Outgoing's 15p, exporting nets about £144/year more than self-consuming — for the car-bound solar alone. On a 24–25p export tariff, that gap widens to roughly £300+/year. Modest, but it's free money you'd otherwise leave on the table, and it grows every time export rates rise.

Two honest caveats on this figure: it applies only to solar that would have gone into the car — solar covering household load should still be self-consumed — and it assumes you can reliably shift the car's charging to the overnight window (which a smart tariff does automatically).

What This Actually Looks Like on Your Driveway

Here's the practical twist. A solar-diverting EV charger like the myenergi Zappi → is designed to do the opposite of what the arithmetic above recommends — it detects surplus solar and pushes it straight into the car, maximising self-consumption. That's the right default when your export rate is poor.

If you've moved onto a strong export tariff, you'd instead let the surplus export during the day and lean on the overnight smart-charging window to fill the battery. Same hardware, different setting. The Zappi still earns its place: in winter, when there's no surplus to export, it schedules cheap overnight charging just the same. The point is to know which mode your tariffs put you in — not to assume "divert to car" is always optimal.

When Self-Consumption Still Wins

Don't over-rotate on the export answer. Charge the car directly from solar when:

• Your export rate is a legacy 4–5p and you're not moving off it — then the maths flips back.
• You have no cheap overnight tariff — without a ~7p window, the alternative to solar is a 25p daytime import, and self-consuming wins comfortably.
• The energy is for the house, not the car — daytime household load can't be time-shifted, so covering it with solar is always worth the full import rate.
• You have a [home battery](/glossary#home-battery) — that's a different calculation again: a battery lets you store cheap-rate or surplus energy and dispatch it at peak, and tariffs like Octopus Flux reward exporting into the evening peak. With storage, run the arbitrage across all three of import, export, and peak windows.

The Bottom Line

The old rule of thumb — "always use your own solar" — was built for an era when exporting paid 4p. In the UK of 2026, with 15–25p export tariffs sitting alongside 7p overnight EV rates, that rule is out of date for EV charging specifically.

The replacement is a single subtraction: if your export rate beats your overnight charging rate, export the solar and charge the car overnight. For most drivers on a modern Octopus, EDF, or Good Energy export tariff, that now means selling the sunshine and buying the night.

Run your own tariffs through the VoltSun calculator to see where your surplus is worth most — and how few pence per mile your setup really costs once the sums are pointed the right way.

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