As you might guess, the achievement comes down to an increasingly diverse range of energy options. Observers at Gridwatch estimate that about half of British energy on the 21st came from natural gas, while the rest was divided between nuclear, renewable and imported energy sources. It wouldn't be accurate to say that Britain went green for 24 hours, then, but there was enough eco-friendly energy that coal wasn't as necessary as it might have been in the past.

You can expect more of this in the future. The UK expects to shut down the last of its remaining coal power plants no later than 2025, and that means longer and longer stretches where coal is absent. Still, the celebration around this achievement sits in stark contrast to the US, where the current government is determined to prop up coal in spite of economic and environmental realities.