£3.2bn to switch off power plants when network cannot cope

Bottlenecks mean turbines must stop generating and gas-fired plants are brought online to keep the lights on, says energy operator

The cost to consumers of paying wind farms and other power plants to switch off because there is not enough capacity on Britain’s transmission network is set to increase by £1 billion to £3.2 billion over the coming year, according to the National Energy System Operator (Neso).

The majority of the cost stems from paying gas-fired power plants to fire up to replace wind turbines in remote locations that have to be switched off due to cabling bottlenecks.

The costs Neso incurs to manage the electricity system are recovered through household and business energy bills. If the forecast increase materialises, it could add about £10 to the average annual household bill, adding further pressure to prices as ministers seek to deliver on their pledge to cut energy costs.

Rising gas prices are driving the bulk of the forecast increase in so-called “constraint costs” because they will make it more expensive to run replacement gas plants, Neso said. 

Costs will also be driven higher because network companies are taking some power lines out of service temporarily to enable upgrades. This should help solve the issue in the long term but will exacerbate bottlenecks in the short term, it said. 

Neso has to ensure that supply and demand are balanced across the network at all times, ensuring there is enough electricity that can get from power plants to consumers without overloading wires. Constraint costs have surged in recent years as wind farms have been allowed to connect to the network before it has been upgraded to reliably transmit all their power to consumers.

Neso is under scrutiny over its ability to manage Britain’s electricity supplies securely after whistleblowers alleged a prolonged drop in frequency on June 23 left the country close to blackouts.

Secret report that exposed the fragility of our electricity system
Analysis by Ben Watts, an energy consultant, showed that on that day wind farms off Scotland had to be paid to stop generating owing to constraints, several large power plants in the south were out for maintenance and subsea interconnector cables to Europe were also exporting power out of southern England. 

Internal Neso reports obtained by The Times showed constraints were breached on five transmission lines — in other words, more power was being sent along the cables than should have been to try to get it to where it was needed during the power crunch. 

Separately, ministers were advised against pressing ahead with an option to switch off digital terrestrial television from 2034 because it is the only communications network capable of continuing to broadcast through a prolonged power cut.

The National Preparedness Commission urged the government to retain digital terrestrial TV until at least 2044, warning that broadband routers fail immediately when electricity supplies are lost and phone masts typically have backup power lasting between 30 minutes and six hours. By contrast, the main TV transmitters can continue broadcasting for about seven days using diesel generators.

Lord Harris of Haringey, the commission’s chairman, said: “The question for government is much more than how people will watch television in future, but how the country will communicate when internet-based systems fail.”

Neso forecasts total constraint costs of £3.2 billion over the coming 12 months, to July 2027. That compares with £2.2 billion incurred over the past 12 months to June 2026 — which came in below Neso’s £2.6 billion forecast for that period.

Neso said constraint costs were highly sensitive to wholesale energy costs, weather patterns, network and generator failures and changes to the network. 

It said that “over 75 per cent of the forecast cost is due to the limitations of the current network”.

Multibillion-pound upgrades are under way to reinforce the network, but that engineering work takes more wires out of service, temporarily worsening the challenge.

“To reduce this element of constraint costs, new network should be built. However, to do so requires outages — increasing constraint costs in the short-medium term,” Neso said. “Where possible, outages are taken in summer, when demand is lower. As more outages are planned, this ‘outage season’ has extended further into autumn and winter than in years gone by.”

Constraint costs are the biggest single element of the costs Neso incurs to balance supply and demand on Britain’s electricity system.

The government said: “The government believes there is a strong case for a long-term transition to IPTV, but no decisions have been made. We understand the importance of information access in times of national emergency and this should be retained beyond a move to IPTV. The purpose of the media green paper is to gather views from across the sector and the public before any final decisions are taken.

“Any future transition would only proceed once we are confident the right safeguards, infrastructure and support are in place.”

Neso said: “We are determined to play our part in keeping balancing costs as low as possible and through new tools, reforms and close collaboration with industry, we have helped to save consumers at least £1.2 billion.

“Keeping balancing costs down over the long term will depend on reforms to the electricity market and continued network expansion, which are outside of Neso’s control. As this build out happens, we will continue to focus on ensuring a resilient and affordable future energy system.”