The internet is becoming ever more full of really incredible real time data. I’ve just found a site that shows the sources of electricity used by the Bonneville Power Administration, Pacific Northwest of America (Site here). This shows power from thermal sources being pretty constant at 3000 – 4000 MW about 1000 MW below the overnight minimum demand. Wind power is shown as providing between no electricity and 4000 MW but there being no control over when it generates. Hydro is clearly the winning technology in terms of load following going from 4000 – 9000 MW on demand.
There are no surprises from this diagram but it does nicely show the variation in demand across the days and the inability of wind on its own to ever provide reliable power to an area. It shows thermal power providing base-load (nuclear can do that as well) and the need for “dispatchable” power. That is energy sources you can ramp up and down to follow demand. Hydro is very good for that. Batteries might be able to do it in the near future – but at a cost.