Monthly snapshot
March 2026 recorded an average grid carbon intensity of 117g CO2/kWh across 1488 half-hour periods. The cleanest period in the month reached 26g CO2/kWh, while the highest period reached 246g CO2/kWh.
Renewable output supplied just over half of measured generation on average. The recorded renewable share was 50.3%. The month sat in the middle of the recent GB carbon range. These figures make the month useful as a benchmark for comparing live dashboard conditions with a completed calendar month.
Generation mix
Wind was the largest source in the monthly mix at 37.5%. Gas followed at 24.6%. Gas averaged 24.6%, nuclear averaged 12.1%, and imports averaged 13.0%.
The renewable share was built mainly from wind at 37.5%, with solar at 6.0% and biomass at 6.8%. That balance matters because renewable months can look similar in headline percentage while being driven by very different weather patterns. A wind-led month often changes overnight and evening conditions, while a solar-led month changes the middle of the day most clearly.
The mix shown here is an average of the published generation percentages for the month. It is intended for month-to-month comparison rather than billing, settlement, or operational decision-making.
Carbon range
The gap between the cleanest and highest-carbon periods was 220g CO2/kWh. That wide range shows why a monthly average should be read alongside the live half-hour view. Short clean windows can sit inside a month that still has a much higher average when demand rises or fossil generation increases.
Coverage and comparison
The report covers 1488 half-hour periods, roughly 31 complete days of public grid readings. Using every available settlement period avoids cherry-picking individual clean or dirty moments. It also makes the monthly page useful for comparing one completed month with another as the report archive grows.
For a quick comparison, watch how gas at 24.6%, imports at 13.0% and nuclear at 12.1% line up against the renewable share. Those three figures often explain why two months with similar wind or solar output can still have different carbon averages. Higher nuclear output can steady the low-carbon base. Higher gas output usually lifts the monthly average, especially when demand is high, renewable output is weaker, or evening peaks are sharper across several consecutive days.
How to read this report
A lower carbon intensity means each unit of electricity consumed caused fewer grams of carbon dioxide equivalent. Renewable percentage measures the share from wind, solar, hydro and biomass in the published generation mix. The figures move with weather, demand, plant availability, imports and market conditions.
Use this page alongside the live dashboard when you want context for current conditions. A live 90g CO2/kWh reading means something different after a low-carbon month than it does during a gas-heavy winter stretch.
Methodology
This report is generated from structured monthly data used by UK Grid Live. Carbon values are summarised from the Carbon Intensity API. Generation mix percentages are averaged from the published monthly mix values used in the reports archive. Source details and caveats are documented on the methodology page.