As National Grid ESO vows to enable a low-carbon system by 2025, Janet Wood takes a look at progress on the ancillary services needed to  run a system without the aid of fossil fuels

National Grid ESO raised headlines earlier this year when it announced plans to operate the grid entirely on low-carbon technologies by 2025. Of course, this would only apply on days when there is sufficient wind and sun for those sources to cover supply. But it represents a shift in priorities.