Millions across the UK could face blackouts this evening as a huge strain is placed on the UK’s energy supply.

The National Energy System Operator (NESO) has called for more electricity generation tonight due to the plummeting temperatures.

A spokesperson for NESO said: “Following the Electricity Margin Notice last night a Capacity Market Notice has now been issued for this evening starting from 4:30pm.

“Both of these notices are part of NESO’s operational toolkit and are routine tools used most winters. These notices are to inform the energy industry of the need for additional electricity supplies to maintain the operational reserve NESO holds whilst operating the national electricity network.

“These notices do not mean that electricity supplies are at risk or that there is not enough electricity to meet demand.”

The operator has said the system was expected to have a shortfall of 1700 megawatts (MW). They have urged power companies to add more capacity to provide a greater safety next of available supply to Brits.

However, there is no suggestion at present that the blackouts or power cuts are “imminent”, the statement says.

NESO oversees Britain’s power and is an independent, expert, impartial body with roles across electricity and gas.

Using their national control room, NESO ensures the supply of electricity from the market always matches demand which is called ‘balancing’ the system.

Energy trader Paul Salvin told Express.co.uk: “With limited availability for NESO to trade across the interconnectors with them already importing to the UK to their maximum, it is the highest chance in years of blackouts with such tight margins.

“Cold weather, no wind, the perfect winter storm.”

Managing Director of energy supply chain company Technivac Ltd, Andrew Hixon, has warned of the security risks that this issue highlights.

He said: “It shows how dependent we are on ‘connections’ and the lack of headroom in margins. Someone like a rogue state could wreck everything by damaging a few pipelines / cables. Energy security is a big issue.”

The notice issued by NESO on Wednesday morning also asked electricity suppliers to declare any “additional demand control available”. This can include asking factories to temporarily switch off to save power.

At the same time as this, wind power output is expected to fall to 2 GW this evening. This is extremely low compared to around 17 GW on Tuesday evening.

The warning further highlights the potential downfalls of the government switching to a power system based mainly on intermittent wind and solar farms, as wind becomes the UK’s single largest power source in 2024.