An industry regulator says Britain is facing "a significant risk" of gas shortages this winter.
Ofgem said that, due to Russia's war with Ukraine, there is a possibility the UK could enter a "gas supply emergency".
This would lead to supplies being cut to power stations which use gas to generate the country's electricity.
Gas-fired power stations generate between 40% and 60% of the UK's electricity.
Ofgem said: "Due to the war in Ukraine and gas shortages in Europe, there is a significant risk that gas shortages could occur during the winter 2022-23 in Great Britain. As a result, there is a possibility that Great Britain could enter into a gas-supply emergency."
If this happens, supplies would be cut to "the largest gas users" which are likely to be large gas-fired power stations which produce electricity to the National Electricity Transmission System.
Energy rationing?
It is not clear if this could result in electricity blackouts, or mean homes and businesses will face energy rationing this winter.
During the Conservative Party leadership campaign, Prime Minister Liz Truss ruled out rationing.
Asked about the risk of blackouts this winter, Ofgem told the BBC: "This winter is likely to be more challenging than previous ones due to the Russian disruption of gas supplies to Europe."
But it said: "Britain is in a good position with little direct import of gas from Russia. Nevertheless, we need to be prepared for all scenarios this winter."