Why plunge pricing events happen
The UK electricity grid is a constant balancing act. Every half hour, supply must match demand precisely. When supply exceeds demand, prices fall. When the imbalance is large enough, prices go negative.
The main driver of plunge pricing in the UK is wind generation. Britain has built substantial offshore and onshore wind capacity: wind supplied approximately 30% of UK electricity in 2025. On very windy nights, that percentage can spike to 60-70% or higher. At the same time, overnight demand is at its lowest point of the day. The result is a grid flooded with cheap, clean electricity that nobody is using.
When this happens, the generators who own wind farms face a choice. They can try to curtail their turbines (waste the energy) or they can bid negative prices into the market, essentially paying someone to consume their electricity. Curtailment wastes renewable energy and costs the generators money. Negative prices at least let the turbines keep spinning.
Octopus Agile passes this wholesale signal directly to customers. When the grid price goes negative, your Agile tariff goes negative. Octopus pays you for every unit of electricity you consume during that window. The unit paid appears as a credit on your bill at the end of the month.
This is not a promotional discount or a loyalty reward. It is the real economics of an electricity market absorbing more renewable energy than it can use at that moment. Your EV charging is the solution to a genuine grid problem. The money you earn reflects that.
How often do plunge pricing events occur?
In 2025 and into 2026, Agile customers experienced approximately 5-10 plunge pricing events per month on average across the year. The distribution is not even. Plunge pricing concentrates in the windier months, particularly January through March and October through November.
Most plunge events occur between 10pm and 6am. This is when grid demand is lowest and wind generation is uninterrupted. The events typically last between one and four hours, with the deepest negative prices often occurring in the middle of the event as the imbalance peaks.
Geography matters. Scotland, particularly the north, and the north of England see the most frequent plunge pricing due to proximity to major wind farms. Agile regions are priced at the regional level, so South West England customers see slightly fewer and shallower events than Scottish customers. The pattern still holds across all regions: winter nights with strong wind forecasts are when to watch for negative prices.
Depth varies significantly. Events of -5p to -10p are common. Events reaching -14p to -20p happen several times a year. The Agile floor is -100p/kWh, though in practice prices below -20p are very rare. Even a modest -5p event on a 60kWh charge produces a £3 credit, and that adds up across a month.
What -14p/kWh actually means for your EV battery
The numbers become very tangible when you apply them to a real EV charge.
A 60kWh battery fully charged during a -14p event earns £8.40 as a credit on your bill. A 75kWh battery earns £10.50. A 40kWh battery earns £5.60. These are not savings versus what you would have paid. They are actual credits added to your account, reducing your total monthly bill.
At -20p per kWh, the figures are: £12.00 credit on a 60kWh charge, £15.00 on a 75kWh charge. The deepest negative price events in recent UK history have been around -30p to -40p/kWh during exceptional wind surpluses, though these are rare.
If you capture four plunge events per month at an average of -14p with a 60kWh battery, the monthly credit total is £33.60. In a good wind month, high-mileage EV drivers on Agile can accumulate £40-50 in plunge pricing credits alone. This offsets not just EV charging costs but a portion of general household electricity spend too.
Combined with regular overnight charging at 3-5p during non-plunge windows, an active Agile EV driver can reduce their net monthly EV charging cost to near zero in winter months when wind events are most frequent.
How to set your car and charger to respond automatically
There are two approaches to capturing plunge pricing: smart charger automation and manual monitoring. Both work. The automatic approach is more reliable and captures events you might sleep through.
OHME Home Pro. OHME natively reads Agile prices in real time. When prices go negative, it detects this automatically and begins charging immediately, regardless of whether charging was scheduled. If your car is already at your target state of charge, OHME may still charge during a plunge event because the credit earned is real value. You can configure this behaviour in the OHME app.
Zappi with Agile mode. The myenergi system similarly pulls live Agile prices and responds to negative price windows through its overnight scheduling. Deep negative prices will trigger charging even outside your set schedule window if configured to do so.
Manual approach. Check AgileAlert's live price dashboard each evening between 9pm and 11pm. Octopus publishes the next day's prices at around 4pm, and by evening you can see if any overnight slots are negative or very cheap. If negative prices appear on the chart, plug in your car and start charging immediately. Run other high-consumption loads simultaneously (dishwasher, washing machine) to maximise your earnings during the event.
The manual approach requires a daily check habit but costs nothing extra in hardware. The automatic approach via OHME or Zappi captures plunge events even when you're not paying attention, including early morning events you'd otherwise miss entirely.
How to get notified via AgileAlert
The most reliable way to track upcoming plunge pricing windows is to check AgileAlert each evening. The live dashboard shows the full overnight price chart including any negative-price segments clearly highlighted.
Make the check part of your evening routine: look at the price chart around 9-10pm, see if anything overnight looks negative or very cheap, and set your charge accordingly. This takes under a minute once you know what to look for. Negative prices show up as bars extending below the zero line on the chart.
Third-party tools such as HomeEnergyBot and the Octopus Home Mini integration can send push notifications to your phone when prices go negative. These are useful supplements but require their own setup. For most users, the nightly AgileAlert check is the simplest and fastest approach.
During periods of high wind forecast, check prices earlier in the evening. If the Met Office is showing strong winds across the UK overnight, negative pricing becomes significantly more likely and you'll want to be ready.
Maximum earning potential in a month with heavy EV use
Let's model a strong wind month for a high-mileage EV driver on Agile with a 60kWh battery.
Four plunge events at an average of -14p, 60kWh each: £33.60 in credits. Six additional overnight charges at 3p average for a full 60kWh: £10.80 total cost. Net EV charging cost for the month: effectively zero, with the plunge credits more than covering the regular charging costs.
In practice, not every charge fills a full 60kWh battery. But even partial charges during plunge events accumulate meaningful credits. A driver who charges 30kWh during a -14p event earns £4.20 that session. Do that six times in a month and you've earned £25.20 in credits before accounting for any regular cheap overnight charges.
This is why active Agile EV management, combining overnight cheap rates with deliberate plunge event capture, is so financially compelling. The annual equivalent of consistent plunge pricing capture ranges from £360 (modest capture rate) to £600 (high-frequency capture in good wind months). Add regular overnight savings at 4p versus price cap 26.11p, and the total annual saving versus standard tariff for a 12,000-mile driver routinely exceeds £1,000.