Delaney Hall

And Angie has a view on how that actually works.

I'm curious, how do you know, kind of minute by minute, how much electricity Phoenix needs?

And then how do you make sure you're generating exactly that amount?

How does that balancing happen?

For the long term, Angie's team looks at stuff like population growth and climate data and new technologies like electric vehicles.

All of that information gets plugged into a long-term forecast that helps SRP make decisions about building new power lines and substations and finding new sources of power.

But there's another planning horizon that is much shorter.

I'm curious, on a more day-to-day basis, how you anticipate the energy needs of Phoenix at any given moment.

Based on that prediction, the Day Ahead team will make an energy plan for the next day.

They look at what power plants are available and what the forecast says about wind and solar, and they consider how much each source will cost to use.

And when you say stack the generation, you know, they're handing them a plan that says you're going to get this much energy from this power plant.

You're going to get this much energy from this plant.

Wind farm.

Do I have that right?

The stack looks like a stacked bar chart, showing the cheapest energy on the bottom, with the more expensive sources layered on top, ready to be used if needed.

And within that stack, different types of power plants play different roles.

There are the weather-based sources, like wind and solar, and if those are available, you want to use them.

When that happens, you want to turn to the sources that are called dispatchable, the ones that grid operators can turn on and off and ramp up or down on command.

That's stuff like natural gas, coal, and hydroelectric.

As Angie says, you can think of the weather-based resources as rain.