[cesarb]

> We produce way more energy than we use. [...] So why generate more than we need? Well, we need to have power available to prevent brown outs

That's not how it works. If you generate more than you need, you will have the opposite of a brown out (overvoltage and/or overfrequency). Generation and consumption of power have to always be precisely matched.

> especially right after work when everyone gets home and flips their light switch (so to speak).

When everyone gets home and flips their light switch, the extra demand slightly reduces the system voltage and frequency; feedback loops on the power plants then increase their generation to match the extra demand.

> Second; it is actually more efficient to keep the generators fully spun up.

Keeping the generators running at their maximum means you have no margin for extra demand or sudden loss of generation (for instance, another power plant or a transmission line having an issue and shutting down). It's better to keep the generators running below the maximum to have a reserve for when these things happen.

[manfredo]

Excess energy is an easy problem to solve: use it to desalinate water, produce hydrogen fuel to power ships, or any of several other uses.