Whither the Weather

For a meteorologist at the nation’s largest public utility, there’s a lot riding on the line. Forecasts help determine which generation assets go online so you can stay warm—at the lowest cost—on the coldest days.

There’s a internet meme out there; maybe you’ve seen it. It’s Eddard Stark from “Game of Thrones,” leaning into a cold wind, saying something like: “Winter is coming. No, wait, it’s warm again. Okay, it’s cold. Winter is coming. Nope, warm again.”

That very much sums up wintertime life in the Tennessee Valley,where high temperatures can hover in the 50s and 60s—even reaching into the 70s—except for a few brief forays into the teens and twenties and even the single digits. Winter in our region is a wild ride.

No one knows this better than Jeff House, senior program manager for TVA’s Short Term Load Planning (pictured above).

House is a meteorologist by trade—he boasts a degree in atmospheric science from the University of Kansas and an MBA from Wichita State—and its his job to forecast weather for the Tennessee Valley and plan down to the megawatt how much energy TVA will need to produce to meet demand, not just on any given day, but any given time of day.

The Man with the Plan

It’s a high-pressure job—if he’s off by even a single degree, that can mean a shortfall of 350 to 400 MW (or a surplus of the same size). “If we’re talking about putting generation assets online,” House says, “a variance of four degrees can be a problem.” For perspective, that’s the amount of energy produced by a nuclear or large coal plant.

Complicating the picture is the need to plan not only for power, but for the most cost-effective power to meet weather conditions. “Because it’s our mission to offer the least-cost power while maintaining system reliability, the group I work with has to plan for engaging the right units at the right time,” he explains. “That means putting the cheapest generating assets on first, then adding the more expensive ones as we need them.”

House’s forecasts have a big impact on BARO (Balancing Authority and Resource Operations, the group he works with), which must figure out which assets to commit and when; decisions change based on whether the Valley facing a long-germ weather front or just a quick cold snap. “We have some efficient plants that can perform better than others on short runs because they are less expensive to start and stop when conditions are volatile,” says House. 

Hydro power is always the cheapest source to turn to in a pickle, House explains: “You can get it on quickly when you need it, but it’s not always available.” That’s especially true this year, when water levels have been abnormally low due to drought.

At other times, the most cost-effective choice might be buying energy from the market. “Just because we’re cold or hot, that doesn’t mean everyone else is,” he says. “If TVA is cold and it’s costing us a certain amount to produce power and the market is going for cheaper, we’ll buy power because that’s the best scenario for the people of the Valley.”

Threading the Needle

Whatever the case, House likes to be proactive. “All your scenarios are bad when you are chasing cold,” he says. “You can easily get burned in one direction or another.” Long story short: When forecasts are off, it can cost TVA money.

“You have to thread that needle with great accuracy,” he says, “and do it fast. Cold is the worst. It tends to come in quickly and leave quickly too. You have to get units on at the right time and back them off at just the right time, too. And everybody knows the Valley weather is crazy.”

Complicating House’s job is the need to plan for the ups and downs of not just the season, but also the day. “In the winter, you need to plan for a big spike right before sunrise as businesses warm up and turn on lights for their daily operation,” he says. “There will be less heating during a sunny day, but a peak again in the evening, before tapering off again at night. There is a definite shape to the days, and we must acknowledge those too.”

House’s load and forecasts go out 14 days, and are broken down by the hour. He uses a variety of modeling tools, including government information provided by NOAA, and a good dose of his own Spidey senses, honed by 20 years of experience on the job.

His note for the rest of this year? More winter IS coming, even though a long-term warming trend has been happening since 2007. “For the past 10 years, we’ve seen a winter warming trend,” he says. “For a utility, regardless of cause, we have to plan for it.”

That’s what he intends to do. Meanwhile, when cold snaps come, you can count on your heater to work and your lights to come on because House and his team at TVA are the job and good at what they does. “Not having power is hard to imagine,” he says. “I intend to keep it that way.”

Balanced Fuel Portfolio Helps Reduce Ratepayer Costs

TVA balances its energy portfolio not only to reduce carbon emissions but to respond to fluctuating coal and natural gas prices to keep customers’ bills as low as possible. Maintaining flexibility among generating resources is the key. Read more about how TVA’s fuel portfolio and low rates connect.