O Rudgard, Spells of fully zero-carbon power by 2025, Daily Telegraph, 15 June 2021, p 12

In UK, the National Grid Electricity Systems Operator reports that the results of overhauls during the next four years will mean that the grid will operate for periods of time (not specified in number or extent!) entirely from renewable sources. As an example, the share produced by coal has fallen from 25% in 2006 to 1.6% in 2020. (This should be read in conjunction with the following abstract)