That depends on the type of solar power. Yes, there's photovoltaic power - though you'll note that the article was talking about mirrors - mirrors heating up something. That something often has quite a bit of heat capacity.

There are quite a few ways to store that thermal energy from solar ( https://en.wikipedia.org/wiki/Solar_thermal_energy#Heat_stor... ) The Ivanpah Solar Power mentioned in the article lacks any storage, but its possible to store steam - the PS10 plant ( https://en.wikipedia.org/wiki/PS10_solar_power_plant ) stores its steam at 50 bar and 285 C for an hour.

Its also possible to do molten salt ( https://en.wikipedia.org/wiki/Thermal_energy_storage#Molten_... ) which can store its heat for up to a week. Solar Two used this in the Mojave back in the late 90s.

The peaker plants aren't necessary when you can just grab some steam or other thermal energy from a tank and use that.

Hydroelectric power ( http://www.energy.ca.gov/hydroelectric/ ) also does a good job of being an instant on (recognizing the issue that California has had for the past few years with hydroelectric power...).

From https://www.forbes.com/sites/jonbruner/2011/10/20/the-high-s...

> Each generator housing contains a 280-ton turbine that looks like a ship’s propeller and a 430-ton generator rotor that spin in perfect synchronization with the grid’s alternating current. As large as these generators are, they’re among the nimblest big sources of power available: Duffus can bring a turbine online in under two minutes and, once it’s running, can summon as much electricity from it as he needs in as little as ten seconds. Each 60-megawatt generator can produce enough electricity to supply roughly 60,000 households, but all of that capacity isn’t needed most of the time.