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Sunny skies help make May Britain’s greenest month yet

May had 266 hours of sunshine, boosting solar generation.

May had 266 hours of sunshine, boosting solar generation.

With no coal on the grid and surging renewables, May was the greenest month ever on Great Britain’s electricity grid.

Over the course of the month, the average carbon intensity of the electricity network was just 143gCO2/kWh. The lowest ever carbon intensity was recorded on Sunday 24 May, falling to just 46gCO2/kWh in the afternoon according to National Grid ESO.

This was driven by the weather, with May setting a new record as the sunniest month on record with 266 hours of sunshine, according to the MET Office. This beat the previous record set in June 1957, when there was 265 hours of sunshine.

The sunny weather allowed solar generation to soar, accounting for 11.45% of the electricity mix over the month. While this is not an overall high, the sunshine meant it was comfortably one of the top power sources and at times made up a third of the country’s electricity mix, according to Roisin Quinn, head of national control at National Grid ESO.

May followed a record breaking April, when UK solar smashed generation records, hitting a peak of 9.68GW and meeting almost 30% of UK electricity demand. Throughout May, renewables saw a peak share of 67.47% of the electricity grid, contributing 28% overall.

Surging renewables over recent months has combined with a drop in demand caused by the COVID-19 lockdown to keep coal off of the grid since 9 April. This helped make May the first full calendar month, a full 744 straight hours, without coal since the industrial revolution.

While the lack of coal has been widely welcomed, demand lows have created challenges for National Grid ESO, which has had to use a range of tools to keep the grid balanced.

Quinn added: “Low demand on the electricity system continues to present our control rooms engineers with a unique challenge – particularly with two May bank holiday weekends within two weeks relaxing already low demand even further.”

The Easter bank holiday weekend at the beginning of the month caused demand to fall to a record low of just on 24.36GW on Saturday 11 May.

On the second bank holiday weekend, day ahead power prices fell to the lowest they have ever been, dropping as low as -£52.03/MWh.

Low demand and surging solar have seen National Grid ESO’s balancing costs jump around £500 million during the COVID-19 lockdown.

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