Why UK Electricity Prices Are Going Negative at Midday
On a growing number of sunny, windy days, the wholesale price of electricity in Britain drops below zero. Not close to zero, actually negative, where generators are effectively paying to keep supplying the grid. It sounds like a glitch. It isn’t, and it’s happening often enough now that it’s worth understanding if you’re weighing up solar, export tariffs or a battery.
How often this is actually happening
This isn’t a one-off. In April 2026, close to 17% of midday half-hour settlement periods on the wholesale market cleared at a negative price. By the middle of 2026, the country had already passed the full-year record set in 2024 for negative-price hours, and 2024 was itself a record year. The driver is simple: solar and offshore wind output has grown faster than the grid’s ability to absorb it, so on a bright, breezy afternoon, supply can outrun demand by a wide margin.
Worth flagging: these figures come from market-tracking sites reporting on N2EX day-ahead settlement data rather than a single official dataset, so treat the exact percentage as broadly right rather than precise, and expect it to keep climbing as more solar and wind capacity connects.
Does this mean my SEG payment goes negative too?
No. The Smart Export Guarantee has a floor built in: Ofgem requires every SEG tariff to pay above zero, always. Your supplier can drop your rate, but they can’t charge you for exporting. See our Smart Export Guarantee guide for how those rates actually work.
What negative wholesale pricing does explain is why some of the newer dynamic or agile export tariffs pay noticeably less, sometimes closer to nothing, during exactly the hours your panels generate most. If the wholesale price a supplier can sell your exported electricity for has gone negative, there’s very little incentive for them to offer you a generous rate for it at that moment. A flat-rate SEG tariff doesn’t reflect this swing at all; a half-hourly agile one reflects it directly.
What it means for a battery
This is the part actually worth acting on. If you’re exporting solar you generated at midday only to buy electricity back in the evening at a normal rate, you’re selling at the worst possible time and buying back at a much better one for the supplier than for you. A battery lets you store that midday generation and use it later instead, sidestepping the weak midday export price altogether rather than hoping your supplier’s rate holds up. It doesn’t change the once-and-done economics of solar itself, but it does shift the economics of adding a battery to it. See our is a home battery worth it guide for the fuller cost breakdown.
Bottom line
Negative wholesale prices are a sign the grid has more solar and wind on it than it can use in that moment, not a fault in your own system, and not something that touches your SEG payment directly thanks to the zero floor. Where it does matter is tariff choice: a flat SEG rate shields you from the swings a dynamic one doesn’t, and if you’re exporting a lot at midday, that’s exactly the generation a battery is best placed to capture instead. Get matched with vetted installers if you’re weighing up whether a battery makes sense for your setup.
Prefer a phone call? Also £250 off your purchase!
Our affiliate partner Blue Ape Renewables install solar, batteries, heat pumps and EV chargers across the UK and are rated 5 stars on Trustpilot. Book a call within as little as 15 mins.
09:00 - 17:15 Mon - Sat.
Affiliate link - we earn a commission if the quote leads to a sale, and you get £250 off your purchase.
Frequently asked questions
Why do UK electricity prices go negative?
When solar and wind generation outstrips demand on a bright or windy day, there's more electricity on the grid than anyone needs at that moment. Generators sometimes pay to keep supplying rather than shut down, which pushes the wholesale price below zero for that half-hour period.
Can my Smart Export Guarantee payment go negative?
No. Ofgem requires every SEG tariff to pay above zero at all times, regardless of what the wholesale price is doing. Your rate can be cut, but you can't be charged for exporting.
Does this make a battery more worth it?
For households exporting a lot of solar around midday, yes. Storing that generation and using it yourself later avoids exporting into exactly the hours when wholesale prices, and often dynamic export rates, are weakest.