GB Electricity Generation Mix Explained: Wind, Solar, Nuclear and More
At any given moment, the electricity powering Great Britain comes from over a dozen distinct sources — offshore wind, onshore wind, nuclear reactors, gas turbines, solar panels, hydroelectric dams, biomass plants, and electricity imported through undersea cables. Understanding the mix, and how it changes, is central to understanding the GB grid.
How the Generation Mix Is Measured
The generation mix is tracked in real time by Elexon, the company responsible for GB's Balancing and Settlement Code (BSC). Every licensed power station above 100 MW must submit half-hourly metered output data to Elexon's Balancing Mechanism Reporting Service (BMRS). Aggregated by fuel type, this produces the generation mix.
Smaller embedded generators — most rooftop solar, and some onshore wind — are estimated rather than directly metered. Sheffield Solar's PV_Live service provides the most accurate estimates of solar PV contribution across all scales.
GB Power Insights pulls generation mix data directly from the Elexon BMRS API, updated every 30 minutes. View the live generation mix →
The Major Generation Sources
Offshore Wind
Offshore wind is now Great Britain's largest single source of electricity generation by installed capacity — over 15 GW as of 2025. Concentrated in the North Sea (Hornsea, Dogger Bank), the Irish Sea (East Anglia Array, Beatrice), and Scottish waters, these vast arrays of turbines can collectively generate more than 15 GW when conditions are favourable.
Key characteristics:
- Capacity factor around 40–45% (among the highest of any renewable)
- Cannot be scheduled in advance — dependent on wind conditions
- Near-zero marginal cost when generating
- Not significantly affected by local air quality or light levels
On the windiest days, offshore wind alone has supplied over 40% of GB demand.
Onshore Wind
Great Britain has over 14 GW of onshore wind capacity, concentrated in Scotland, Wales, and northern England. Onshore wind is cheaper to build than offshore but faces greater planning constraints.
Key characteristics:
- Capacity factor around 25–35%
- More variable than offshore due to surface wind turbulence
- Significant contribution from Scotland, which exports south via high-voltage transmission lines
Together, onshore and offshore wind regularly supply 35–50% of GB demand on windy days, and occasionally exceed 70% during exceptional wind events.
Nuclear
Great Britain's nuclear fleet provides reliable, round-the-clock low-carbon generation. As of 2025, the fleet includes stations at Heysham, Hartlepool, Torness, and Hinkley Point B (with Hinkley Point C under construction). Total operational nuclear capacity is around 5–6 GW, down from historic peaks as older AGR (Advanced Gas-cooled Reactor) stations approach closure.
Key characteristics:
- Generates continuously — not weather-dependent
- Near-zero carbon emissions (lifecycle ~12 gCO2/kWh)
- Cannot be flexed up and down quickly — runs as "baseload"
- Typically supplies 10–20% of GB demand
Nuclear is particularly valuable in winter, when solar output is low and calm-wind periods are more frequent. The fleet's gradual retirement without immediate replacement is a key challenge for GB's low-carbon future — hence the new construction at Hinkley Point C and planned investment in small modular reactors (SMRs).
Gas (CCGT and OCGT)
Combined Cycle Gas Turbines (CCGTs) and Open Cycle Gas Turbines (OCGTs) remain the single largest source of electricity in GB on most days. Gas is the "flexible" backbone of the grid — it can be turned up or down within minutes to balance variable renewables.
CCGTs (combined cycle) are efficient large plants that capture waste heat to generate steam, improving efficiency to 50–60%. They are used for extended periods of mid-merit generation.
OCGTs (open cycle) are less efficient but faster to start — useful for rapid response to demand spikes or unexpected plant failures.
Key characteristics:
- Emits around 400–450 gCO2/kWh
- Supplies 20–50% of demand depending on renewable output
- Gas price directly drives wholesale electricity price
- Essential for grid security during low-renewable periods
Solar PV
Solar generation has grown from near-zero in 2010 to over 15 GW of installed capacity across Great Britain. It consists of:
- Large solar farms (50 MW+) — directly metered via BMRS
- Rooftop commercial solar — estimated by regional models
- Domestic rooftop solar — estimated by Sheffield Solar PV_Live
Solar's contribution is highly seasonal. In June, solar can supply 8–10 GW at peak (10am–2pm BST), accounting for 20–25% of midday demand. In December, peak output is less than 2 GW and the generation window is short.
Track live solar output on GB Power Insights →
Biomass
Biomass — primarily the converted Drax power station in Yorkshire — burns compressed wood pellets (predominantly imported from North American managed forests) to generate around 2–2.5 GW of reliable electricity. Biomass is classified as "low-carbon" under current UK accounting rules on the basis that trees are replanted.
Key characteristics:
- Dispatchable (can be controlled like gas or nuclear)
- Controversial carbon accounting — lifecycle CO2 from wood pellets is significant
- Currently provides valuable flexibility alongside intermittent renewables
- Government subsidies (ROC and later CfD) have supported its expansion
Hydro
Great Britain's hydroelectric capacity is around 4 GW including pumped storage, concentrated almost entirely in Scotland. Conventional run-of-river hydro supplies around 0.5–1 GW continuously when reservoirs are full.
Pumped storage (Dinorwig "Electric Mountain" in Wales, and Cruachan in Scotland) is different — it acts as a giant battery. Water is pumped uphill during low-demand periods (often overnight when nuclear and wind are running) and released through turbines during peak demand. Pumped storage capacity is precious and provides rapid response within 12–16 seconds.
Interconnectors
Great Britain is connected to neighbouring electricity systems via high-voltage direct current (HVDC) cables:
| Link | Counterpart | Capacity |
|---|---|---|
| IFA1 | France | 2 GW |
| IFA2 | France | 1 GW |
| Nemo Link | Belgium | 1 GW |
| BritNed | Netherlands | 1 GW |
| NSL | Norway | 1.4 GW |
| Viking Link | Denmark | 1.4 GW |
| Moyle | Northern Ireland | 0.5 GW |
| East-West | Republic of Ireland | 0.5 GW |
Total interconnector capacity exceeds 9 GW. Imports appear as a generation source in the mix; exports appear as negative generation (or as demand).
France's predominantly nuclear grid means French imports carry very low carbon (around 70 gCO2/kWh). Norwegian hydro imports carry near-zero carbon. Dutch and Belgian imports vary depending on their own grid mix.
How the Mix Changes Through the Day
Here's a typical summer weekday profile for GB generation:
Midnight–6am: Nuclear (steady), wind (high if windy), gas (low-moderate), pumped storage discharging if needed
6am–9am: Gas ramps up for morning peak, solar starts rising, wind continues
9am–2pm: Solar peaks (midday), gas reduces, wind continues, nuclear steady — lowest carbon intensity of the day
2pm–5pm: Solar starts declining, gas holds moderate, wind continues
5pm–8pm: Solar drops to zero, gas ramps sharply for evening peak, pumped storage discharges — highest carbon intensity of the day
8pm–midnight: Demand falls, gas reduces, wind may be high, nuclear steady
The Direction of Travel
The GB generation mix has undergone a transformation in 15 years:
- Coal: from 40% of generation in 2010 to zero in 2024 (last coal plant closed)
- Wind: from ~3% in 2010 to regularly 35–50% on good days
- Solar: from zero in 2010 to 10–25% during summer middays
- Gas: reduced but still dominant in winter and evening peaks
- Nuclear: stable but declining as old AGRs retire
The trajectory is clearly toward higher renewable penetration. The challenge is maintaining grid stability and affordability as weather-dependent generation increases. Battery storage, demand flexibility, hydrogen, and interconnectors will all play a role in managing the increasingly renewable future grid.