The milestone has been passed for the first five months of 2019. National Grid says clean energy has nudged ahead with 48% of generation, against 47% for coal and gas, BBC reported.
The rest is biomass burning. The transformation reflects the precipitous decline of coal energy, and a boom from wind and solar.
National Grid says that in the past decade, coal generation will have plunged from 30% to 3%.
Meanwhile, wind power has shot up from 1% to 19%. Mini-milestones have been passed along the way. In May, for instance, Britain clocked up its first coal-free fortnight and generated record levels of solar power for two consecutive days.
The shift is being driven by the need to cut emissions of the greenhouse gases that are over-heating the climate. The electricity sector was seen as the easiest place to start.
"Over the last 10 years there’s been real progress in de-carbonization of the energy system – but 2019 is going to be a key milestone,” John Pettigrew, CEO of National Grid, said.
"It's the first time since the Industrial Revolution that more electricity has been produced from zero and low-carbon sources rather than fossil fuels. It's tremendously exciting because it's such a tipping point," he added.