[thackney]

The plants have to be made MUCH larger than the normal amount of electricity they need to provide, because they also need to provide power at peak demand which is much higher.

No. That is not how it is done.

Fast starting Gas Turbines and the like are used to ramp up and down with load changes. They are shut off as the load drops back down. The other plants are mostly base loaded to operate efficiently.

[Prophet2520]

“No. That is not how it is done.

Fast starting Gas Turbines and the like are used to ramp up and down with load changes. “

In some cases you are right. That is kind of an over generalization but my statement was a generalization and simplification as well. I have no interest in debating how centralized power plants work or are designed. My point is that energy storage is increasingly being considered as important at the grid level.

Here is a starting point on that if anyone is interested.
http://energy.gov/oe/downloads/grid-energy-storage-december-2013

[Robert A Cook PE]

Fast starting Gas Turbines and the like are used to ramp up and down with load changes. They are shut off as the load drops back down. The other plants are mostly base loaded to operate efficiently.

Those “fast startup” and fast shutdowns (two start and shutdown cycles each day, if not more often when wind turbines are also involved) literally destroy the gas turbine casings and exhausts. Parts that should last 12 years crack in two in 18 months.

Single cycle gas turbines are much less efficient: a fast startup gas turbine is 38 to 42% efficient, a combined cycle GT is 62% efficient.