Delaney Hall

the transmission lines eventually run into substations.

Before it goes into the house, it's stepped down once again by a transformer, which is often located on top of a utility pole outside your home.

Again, this is for safety, so that an elephant-killing dose of electricity isn't flowing into your house.

The amazing thing about this system, the generation of power and then the movement of electricity through power lines to the home, is that it happens incredibly fast.

And here's another amazing thing about this system.

Historically, the grid has not had much storage capacity.

This is changing quickly.

Grid-scale battery storage is a very hot field right now, and it's important for renewables.

But for most of the grid's history, electricity has typically been consumed almost the instant that it's produced.

As Gretchen says, it's fresh.

And it makes sense to do it that way.

If you can deliver electricity on demand, it doesn't really make sense to spend billions of dollars building giant batteries to store it.

It would be like running a restaurant and deciding to build a massive warehouse to stash the meals when you could just cook them to order instead.

This metaphor doesn't totally work because electricity doesn't go bad like food, but you get it.

But when you're delivering electricity on demand, the grid has to stay in perfect balance.

Meaning the amount of power being generated has to match the amount being used pretty much exactly every second of every day.

Because what's really being maintained is that precise frequency of 60 back and forth cycles per second.

That frequency of 60 hertz synchronizes every power plant, every transformer, and every home on the grid.

If demand suddenly exceeds supply, the frequency drops, and the whole system gets out of whack.

Cascading failures can knock out the grid entirely.