National Grid left the lights on in every window of its near-empty HQ after most workers would have gone home.
The energy giant warned last week that blackouts might be needed for energy rationing due to Russia’s invasion of Ukraine, which has destabilised the market.
However, it has now been accused of hypocrisy after pictures taken on Monday evening showed lights left on in almost every office of its headquarters in Warwick.
Peter Kearns, 49, who works locally, said: “The place is lit up like Blackpool illuminations and National Grid of all people should be setting an example to the rest of the country - now more than ever.
“Other offices make sure their lights are off when they leave for the day, so they should do the same, especially when they are talking about winter blackouts.
“They are telling us all how to prevent the National Grid from collapsing - while seemingly doing nothing at all to stop that happening themselves.”
Liz Truss has refused to rule out the prospect of widespread blackouts for up to three hours a day this winter if the country is unable to import enough energy.
National Grid has warned that both households and businesses are at risk of being cut off.
It said a worst-case scenario could include “load shedding”, where power is restricted to different areas at different times to prevent uncontrolled outages.
Homeowners will be asked to use their washing machines and other electricity appliances at night to help avert potential disruption during peak hours. Under other contingency plans, households and businesses could be handed £10 a day to stop using electricity when needed.
A plan for rolling blackouts, not used since the 1970s, would need the approval of the Government and the King.
Britain may need to import gas from continental Europe to meet demand in the event of a cold winter, but these supplies could be at risk because of Russia’s invasion of Ukraine.
The leaders of Belgium and the Netherlands promised to keep working with Britain to protect Europe’s energy security.
A National Grid spokesman said: “Our Warwick office houses operational control rooms for gas and electricity where engineers work in shift patterns 24/7 to keep the lights on and gas flowing across the United Kingdom.
“The building has many energy conserving measures including sensor controlled lighting which turns itself off automatically if a room is empty.”
