It's an interesting area, and I don't pretend to understand it, but the more I look, the more a flat price seems absurd.
I was interested to find out how much it costs the grid (and consumer) to move generation to gas in areas where demand is high (e.g. London), but there is not sufficient local generation, even though there is wind constraint on generation in other locations (e.g. Scotland).
I found
this article , which links to
this report. If I am understanding correctly, page 33 and 34 discusses exactly this cost, and the price we pay to turn off wind is about 1/3rd of that which we pay to turn on gas to meet the demand. I.e. on very windy days in Scotland, we pay generators to turn off the incredibly cheap energy, but then pay gas to generate in low wind areas, and that peak generation set the price for consumer everywhere - including right next to the very cheap, still operating wind turbines. Is this a good understanding?