system
Given the following post, respond as if you're commenting on Reddit:
human
In modern steam power plants, can the amount of power output be managed?

In modern power plants that heat water, make steam, and turn turbines through steam power, is the output set, or can the operators feed it less fuel, produce less heat, create less steam, and output less power?

I'm curious due to the nature of the power grid, where excess power just goes to ground.  It is such a big waste, I'm wondering if the plants can throttle the output during non-peak times and ramp it up during peak times.

Thanks!
gpt
Different power plants have different responses, and different time scales.  A combined gas cycle plant, running off Natural gas can respond to the grid very quickly increasing its power output.  They are often used as load balancers as they are rather expensive to use all the time.  

Other plants such as a nuclear plants cannot easily increase or decrease their power usage in a short time scale.  They are used as a baseline load.  If there is an outage, or suddenly power usage drops quickly they must dump power, or shut down.  As shutting down is expensive you can have a resistive load balancer which will drag down the grid voltage to keep it in line with specs.  This is basically a industrial sized coffee maker that heats water.  

Generally for non emergency load balancing water is often used.  They will pump water in reverse in a hydro plant, then when they need more power they allow it to run through the turbines again.

Renewables such as solar and wind are not comparable, as they have very strange power responses, and are controlled by forces outside of human control.  However they are such a small part of the grid, it doesn't really matter.  If percentage is to be increased, this needs to be addressed.