Millions of households will be paid to use energy outside peak hours this winter through a new scheme - as experts warn there could be blackouts.
System operators said an "unlikely" shortage of gas could result in families suffering planned three-hour power cuts to protect energy supplies.
It said the number of people left without electricity - and which areas could be affected - would depend on how many gas power stations would be forced to shut down.
This is the worst-case scenario presented by the National Grid Electricity System Operator (ESO) as part of a new report.
It still expects energy demand and supply to be sufficient to cover households this winter.
"In the unlikely event we were in this situation, it would mean that some customers could be without power for pre-defined periods during a day - generally this is assumed to be for three-hour blocks," the ESO said.
To help avoid blackouts, families will be being encouraged to sign up to a new a scheme which will give them money back on their bills to use appliances outside of high demand times.
For example, this could be using your washing machine or dishwasher at unsociable hours, or charging your electric car outside peak times.
The newly launched service will work as an opt-in system for those with a smart energy meter.
Households would receive a text message asking them to only use electricity when there is less demand - typically after 7pm.
In exchange, they would receive a payment.
Larger businesses will be paid for reducing demand, for example by shifting their times of energy use or switching to batteries or generators in peak times.
The "Demand Flexibility Service" will run from November to March. It is expected to be implemented at least 12 times and should deliver two gigawatts of power savings.
The ESO's director of corporate affairs, Jake Rigg, said: "The demand flexibility service is a first of its kind and a smart way for signed up consumers in homes and businesses to save money and back Britain.
"If you put your washing machine or other electrical appliances on at night instead of the peak in the early evening, you can get some money back when we all need it.
"The service is due to launch in November, so watch out for further details soon. This really is a window into the future where a flexible energy system will be cleaner and lower cost to alternatives."
However, if those measures fail, and demand for electricity exceeded supply, households and businesses could see their power switched off for up to three hours at a time.
Officials stressed that customers would be told in advance. Vital infrastructure such as hospitals would be excluded from the cuts.
The National Grid today said there are two gigawatts of coal-fired power plants on stand-by, if needed to meet demand.
This deal has been struck between three power companies - EDF, Drax and Uniper - in case of a loss of imports from France, Belgium and the Netherlands.
The National Grid admitted that households face a "challenging" winter following the Russian invasion of Ukraine, which has contributed to soaring energy prices.
The crisis has led to gas flows from Russia to Europe being cut off.
Britain is far less reliant on Russian gas compared to mainland Europe - but there could still be knock-on effects for families.
The ESO base case assumes that when Britain needs more electricity, cables that link the country to its European neighbours will be enough to keep the lights on.
It does not assume that there is any "material reduction of consumer demand due to high energy prices".
Responding to the winter outlook, a Government spokesperson said: "The UK has a secure and diverse energy system.
"We are confident in our plans to protect households and businesses in the full range of scenarios this winter, in light of Russia's illegal war in Ukraine.
"To strengthen this position further, we have put plans in place to secure supply and National Grid, working alongside energy suppliers and Ofgem, will launch a voluntary service to reward users who reduce demand at peak times."
The spokesperson said Britain is not dependent on Russian energy imports.
They added that there is access to North Sea gas reserves, imports from Norway, and via ports which can handle liquefied natural gas, as well as clean energy sources.
