The UK is forced to ask Belgium for electricity to avoid rolling blackouts, The Telegraph reported.

The Electricity System Operator (ESO) has issued an emergency instruction to operators of the Nemo cable running between Belgium and the UK to make sure supplies to the UK are uninterrupted after failing to provide enough electricity to the regular market.

Experts said this calls into question the power grid's ability to deal with the "looming iceberg" of winter, when gas supplies are expected to come under much greater pressure and Russia could cut off supplies to Europe altogether.

At one point last week, ESO paid a record high price of £9,724 per MWh to import electricity via the Nemo cable, data from market analyst EnAppSys reveals, amid power struggles in Europe.

Two days of record temperatures last Monday and Tuesday also put power supplies at risk. The heat reduced the efficiency of solar panels and other generators and disrupted power lines, while demand rose and wind power fell.

ESO stated that the automated market signals do not take into account all of its data and tools, and it is confident that the electricity margin is sufficient.

This comes as ESO is set to release its early electricity supply and demand forecast this winter this week amid heightened energy security concerns due to the war in Ukraine.

Although the heat wave created particular problems last week, energy demand is usually higher in winter. Cold snap, in particular, can cause chaos in the infrastructure.

The UK gets most of its electricity from its own gas-fired power plants, nuclear power plants, wind turbines, biomass and solar power plants. It also trades electricity with the continent through a growing network of cables capable of supplying more than 10 percent of UK demand.

Supply and demand must be constantly balanced across the network to avoid blackouts, and ESO is stepping in to iron out the imbalance left by the market.

The system across Europe is currently overloaded, with half of the French nuclear fleet offline due to maintenance or corrosion issues, and hydropower generation also low. Although some French nuclear plants will resume operation by winter, the capacity will still be below normal. There are also fears that Russia will further cut off gas supplies to Europe.

Coal-fired power plants in the UK and on the continent have been asked to remain in operation longer than previously planned. The UK usually imports electricity from France during the winter to meet its own demand.