National Grid aims to replace Sizewell footroom with small generators


When its multimillion pound contract with EDF comes to an end, National Grid ESO aims to work with smaller generators, including wind and solar farms, to provide system footroom on a more permanent basis.

As transmission system demand collapsed following lockdowns, the ESO struck a deal with EDF to halve output from Sizewell B, originally worth between £34m and £46m.

It took that approach after scenario planning suggested demand could fall as low as 13GW. Because nuclear plant is inflexible and tends to run regardless of market prices, the ESO expected around 5GW of nuclear generation to be on the system, alongside 8-9GW of must run plant, i.e. large power stations required to provide voltage and stability services.

“Suddenly you get to a point where you are unable to balance the system,” according to Matt McGill, strategy manager for commercial electricity operations at the ESO.

It also quickly developed a market-based footroom tool, ODFM, which pays distribution-connected generators to stop exporting power to the system, or others, such as batteries or industrial consumers to draw more power.

To date, generation totalling 4.5GW has signed up to ODFM, which has been used four times over summer at a total cost of around £7m.

Three of those activations occurred over the second May bank holiday, when transmission demand hit a new low on 06:00 on 24 May. The ESO recorded demand of 14.5GW, but was running 800MW of ODFM at the time.

“Without that, demand would have been 13.7GW, significantly lower than anything we have ever seen before,” said McGill.

Since lockdown eased, demand has climbed back almost to normal. While the August bank holiday looms, and EDF’s deloading contract was set to expire this week the ESO appears to be out of the woods.

However, it remains keen to attract more providers to the service, scheduled to run until 31 October. The 4.5GW signed up to date has been “predominantly wind and solar”, according to ESO account manager, Richard Hanson.

“This is the first time we have actively contracted with solar … and there’s also been a lot of embedded wind making its way into balancing services for the first time,” he added. “It’s been a huge step in terms of diversifying technologies.”

While the ESO ultimately hopes to bring ODFM providers into the Balancing Mechanism, its main balancing market, Matt McGill said Grid is “looking at how we can move them into a new service,” when EDF’s Sizewell contract comes to an end. “We are doing that with industry feedback on the implementation and there is lots more to come on that.”

In the meantime, he commended the energy industry for stepping up when demand dropped.

“It’s been a challenging first half of summer. We’ve seen demand increase since restrictions lifted, but it’s a testament [to the entire industry] that the lights have stayed on and we have been able to do this.”

Richard Hanson and Amy Weltevreden detailed ODFM via a Power Responsive podcast, where Matt McGill outlined the ESO’s summer challenges. A number of industry experts also provide further insight on flexibility via the podcasts. Listen here.

Update: EDF has extended its contract to reduce Sizewell B output until September. This story originally stated the contract was set to expire mid-August.


  1. The more balancing, the more profits for investors. The more Wind And Solar Plants (WASPs) on the grid, the more balancing needed; the more profits for investors.

    What’s not to like about lobbying forcefully for more renewables and hinting at the blame for the problem is ‘inflexible’ base-load, nuclear power.

    Make the most of it you WASP investors because, come 2030, when GE Hitachi’s BWRX-300 Small Modular Reactor (SMR) is available for manufacture under licence in the UK, the subsidised-good-times will be at an end!

    Fund managers will be clawing at one another’s throats to get their pots out of WASPs and into these 300 MW SMRs, with their 2 years build programme – no different to WASPs.

    On a level playing field, every £1.00 invested in an onshore wind farm (by far the most profitable of intermittent technologies) will ‘earn’ £0.70. £1.00 invested in a BWRX-300 will ‘earn’ £5.02 – 17.2X more.

    The 2 or 3 decades of ridiculous WASPs will be consigned to the ‘Waste-of-Time’ dustbin of history.

    Search for: £320 million to invest, should you: invest now in onshore wind


Please enter your comment!
Please enter your name here