The UK has a stupid system where the pricing for everything is determined by the most expensive thing in the mix:

>The UK’s electricity market operates using a system known as “marginal pricing”. This means that all of the power plants running in each half-hour period are paid the same price, set by the final generator that has to switch on to meet demand, which is known as the “marginal” unit.

i.e. if you have 99 units of solar but have 100 demand, 1 unit of gas plant fires up to fill it then all 100 units are compensated at the gas rate even if the wind was cheap.