In light of news that [Britain just went a week without burning coal](https://earther.gizmodo.com/britain-just-went-a-week-without-coal-for-the-first-tim-1834609354), I was doing some reading and found this interesting discussion over on skeptics.se from a similar occurrence a few years ago: [During Great Britain's coal-free day, were coal plants shut off, or active and generating power GB didn't use?](https://skeptics.stackexchange.com/q/38227/38403)

There were some good answers but ultimately no-one was able to come to a conclusion to my question here: **How much coal do plants burn when they're not supplying electricity to the grid?**

I assume when starting a plant it takes time for the fire to get hot enough to start generation, and similarly when shutting down the turbines, the coal in the burner will burn itself out (unless it's smothered). But how much coal is this? 

Similar to the question on [shutting off a car's engine at a stoplight](https://sustainability.stackexchange.com/q/666/3379), I'm wondering if keeping a coal plant running might, in some circumstances, result in less emissions than stopping and restarting it for the same amount of generation. But to know this, I'd need some data on how much coal is burnt when not generating.