[desipis]

CCGT plants aren't generally used for handling peaks and unpredictable loads. They handle load change better than coal plants, however the grid usually has to depend on OCGT or batteries for stabilising the impact of unpredictable renewables (or unpredictable demand). Both these solutions are expensive and add significantly to the overall cost of pushing more energy generation to renewables.

[makomk]

OCGT is used for short-term peaks, but at least here in the UK the bulk of the work of smoothing out the gaps left by renewables and demand variation over longer time periods (hours or more) is done by more efficient CCGT plants. This is usually pretty visible on gridwatch.co.uk - you can see the level of CCGT generation varying from day to day as wind generation rises and falls.