There are many milestones to pass in the transition from a high to low-carbon sustainable energy system. There is the first hour without coal, or oil, or gas generation (or all of them together) and the point when the last coal, oil or gas power plant (or all of them together) are finally retired.
Another milestone that feels important is the first year when renewables generate more electricity than fossil fuels. For the past three months we have been tracking the data for Great Britain (not Northern Ireland, which shares an electricity grid with the Republic of Ireland) and we believe it is on track to pass this milestone in 2023, but it will be very close.
