GridMonkey — Britain's electricity, live

Questions, answered

Where does GridMonkey's data come from?

Britain's figures come from two official, free sources. The headline generation mix, the carbon intensity and the 48-hour carbon forecast come from the Carbon Intensity API run by NESO, Britain's National Energy System Operator (formerly National Grid ESO). The 5-minute demand, interconnector flows and per-generator output come from Elexon (the GB electricity market operator), joined to Elexon's BM Unit register so each unit can be attributed to its station, fuel and owner. Nothing is scraped — GridMonkey reads the public feeds live in your browser. The Europe view's neighbours come from their grid operators' open data (RTE, Elia, Energinet, EirGrid, and Statnett, Norway's, which also publishes Sweden's, Finland's and the Baltic states') and Germany's from Energy-Charts (Fraunhofer ISE), gathered by GridMonkey every few minutes. Austria, Czechia, Poland, Luxembourg, Italy and the Netherlands publish theirs through the ENTSO-E Transparency Platform, which GridMonkey doesn't read yet, so they are shown without figures for now; Switzerland publishes no live mix, so it is shown without one.

When is the best time to use electricity today?

When the grid is cleanest, and GridMonkey's forecast works that out for you. It reads NESO's carbon intensity forecast and finds the cleanest run of 1 to 4 hours in the next 24, for Great Britain or for your own region from your postcode, and shows the dirtiest stretch too. That's the time to run the dishwasher or washing machine, charge an electric car or boost a heat pump or hot-water cylinder. It is often overnight, or the middle of a windy or sunny day; the early evening, when solar fades and demand peaks, is usually the dirtiest. On a time-of-use tariff the cleanest hours are often the cheapest too, since both follow the wind and the sun, but GridMonkey shows carbon, not price.

How often does it update?

The national mix and carbon intensity refresh every half hour, because Britain's true mix includes the solar power generated on rooftops and in fields, which is only published per half-hour settlement period. Demand, interconnector flows and the by-generator views refresh every 5 minutes — Elexon's fastest public feed, and about as close to real time as GB grid data gets. You can flip the pie to a 'Transmission' view to see that faster, solar-free picture. The best-time forecast is NESO's own, revised every half hour.

Is GridMonkey free?

Completely free, with no sign-up and no ads. It runs entirely in your browser and works on phone, tablet or desktop.

Can I see individual power stations, wind farms and owners?

Yes. As well as grouping the pie by fuel, you can switch it to show live output by company, by power station (Drax, Sizewell B, Torness…), by wind farm (London Array, Hornsea, Dogger Bank, Seagreen…) or by solar farm (the eight that report their own output). The wind-farm view even shows how hard each farm is running versus its capacity, and can roll the farms up to their parent owner (Ørsted, SSE, RWE, ScottishPower…). The fuel, wind-farm and solar-farm views also switch from a pie to a map of Britain, so you can see where the power is coming from right now.

Why doesn't the total match my electricity bill or my region?

The pie shows Great Britain's generation as a whole — not your supplier or your local area. On the physical grid, electrons aren't tagged by supplier: your retail supplier (the company you pay) buys from the wholesale market, so there's no live 'who's supplying me' figure — only market share, which is a slow statistic. The by-generator views also cover transmission-connected stations only, so small embedded generators and rooftop solar aren't itemised there. For your own area, set the forecast to your postcode: it switches to NESO's figures for your region.

Why is electricity cleaner in some parts of Britain than others?

Because of what's generating nearby and how much power has to flow in from elsewhere. NESO splits Britain into 14 regions and estimates each one's carbon intensity: Scotland, with its wind and hydro, is often under 50 g/kWh, while the south of England, which leans more on gas and imports, can be several times higher at the same moment. GridMonkey's map shows all 14 right now, and if you put your postcode into the forecast it uses your region's figures. Only the first half of the postcode is used (BH16, say): it goes straight from your browser to NESO to find your region, and we never see it. Northern Ireland isn't covered, as it's on a separate grid.

What is carbon intensity?

It's the grams of CO₂ emitted for every kilowatt-hour of electricity used, right now — NESO's half-hourly figure. It rises when Britain leans on gas and falls when wind, solar and nuclear dominate. GridMonkey shows the live number, a colour-coded 'very low → very high' band, the last 24 hours and a forecast of the next 24, so you can see the cleanest and dirtiest times of day.

Is a heat pump lower-carbon than a gas boiler?

On Britain's grid today, yes, and by a wide margin. GridMonkey's heat pump tile shows it live. A heat pump's emissions per kWh of heat are the grid's carbon intensity divided by its seasonal efficiency (SCOP, typically 2.5 to 4); a gas boiler's are about 233 g, mains gas at SAP 10.2's 210 g/kWh burned at 90% efficiency. With the grid at 150 g and a SCOP of 3, the heat pump emits 50 g per kWh of heat, about 79% less. The tile also shows the comparison at the dirtiest half hour of the next 24, and lets you change the SCOP.

Can I leave GridMonkey running on a TV or office screen?

Yes. Display mode fills the screen with the live pie, the big numbers and the cleanest time to use power, in dark colours that suit a TV, with a clock. It keeps the screen awake where the browser allows, hides the mouse pointer and refreshes on its own, so it can run all day in a reception, a classroom or a plant room. Tap the screen, move the mouse or press a key and the switches appear, to change the view (pie, map or Europe) or what it shows; they hide again a few seconds later. On a screen without room for both, the Europe map takes the width of the big numbers and forecast while it shows. Use the 📺 button at the top of the app on a larger screen, or open energycount.co.uk/tools/grid-mix/app/?display=1 on the screen itself.

Can GridMonkey remind me when electricity is cleanest?

Yes, two ways. Add to calendar saves the cleanest window as an event on your phone or computer, with a reminder five minutes before. Daily alert sends a notification each day when the cleanest run between 7am and 10pm starts, for Great Britain or your own region. On an iPhone, add GridMonkey to your Home Screen first, as Apple only allows notifications from installed web apps. The alert stores only your browser's notification address, the region and the length you chose, and you can turn it off in one tap.

Is the cleanest time also the cheapest on Octopus Agile?

Often, but not always. Both follow the wind and the sun, so windy nights and sunny afternoons tend to be cheap and clean, but prices also follow demand and gas prices. Tick Compare with Octopus Agile prices in GridMonkey and the half-hourly Agile prices for your region appear under the carbon forecast, with the cheapest window marked, so you can see where they line up. GridMonkey isn't connected to Octopus; the prices come from Octopus Energy's public price list.

How can I tell if a power station like Sizewell B is running?

Open its page under energycount.co.uk/tools/grid-mix/power-stations/. It shows what the station plans to generate this half hour, from Elexon's data, as a share of its capacity, and its output every half hour over the last 7 days. Nuclear stations stop now and then for refuelling and repairs, gas stations come and go with the wind and the evening peak, and pumped storage and battery stations swing between generating and charging, which the page shows as pumping or charging.

Is there an API for the cleanest time to use electricity?

Yes, free and with no key: energycount.co.uk/grid/best.json gives the cleanest 1 to 4 hours for Great Britain, any of the 14 grid regions or a postcode area, from NESO's carbon intensity forecast. The GridMonkey API page explains every field and has a Home Assistant recipe that switches something on when the cleanest hours start. Please ask no more than once every 30 minutes; the forecast changes once a half hour.

How clean was Britain's electricity last month?

See the monthly grid reports at energycount.co.uk/tools/grid-mix/reports/. Each month since May 2018 has its average carbon intensity, its mix of wind, solar, gas and nuclear, its cleanest and windiest days, and how it compares with the same month a year before, all from GridMonkey's half-hourly copy of NESO's figures.

Is there a page for each wind farm?

Yes. Every wind farm that reports to Elexon has its own page under energycount.co.uk/tools/grid-mix/wind-farms/, with what it is generating right now, its registered capacity, its grid region and owner group, and its output every half hour since 17 October 2026. In the app, tap a farm's name in the wind-farm table to open it. The wind-farm list also has a live map of them all, each farm sized by its capacity and coloured by how hard it is running.

Can I see what a solar farm is generating right now?

For the eight solar farms that report their own output to Elexon, yes: each has a page under energycount.co.uk/tools/grid-mix/solar-farms/ with what it is generating this half hour, as a share of its capacity, and its output every half hour since GridMonkey began recording it. Cleve Hill Solar Park in Kent, the biggest solar farm operating in Great Britain, is one of them. Most solar farms, and every rooftop panel, don't report one by one: NESO estimates what they generate across the country, and that is what GridMonkey's pie shows.

Can I show Britain's live grid mix on my own website?

Yes, free. There's a small live badge, showing how low-carbon Britain's electricity is right now with the carbon intensity and the mix, for a footer, sidebar or blog post, and the full interactive chart for a page of its own. Copy either from the 'Put GridMonkey on your site' section on this page. Both update on their own.