As North Carolina continues decarbonizing its energy supply, giant batteries are one tool for keeping the lights on when the sun isn’t shining and the wind stops blowing.
Duke Energy brought a 50-megawatt battery online this week near the former Allen coal plant site in Gaston County. This 54-unit battery can store 200 megawatt-hours of energy at a time — enough to power about 50,000 homes for up to four hours. On a full charge, the battery could keep the lights on in every house in Belmont for over a day. That’s based on the energy consumption of the average American home.
The site previously hosted a 1,100-megawatt coal plant, which Duke Energy retired in 2024. Already, the easily recognizable red-and-white smokestacks have come down, leaving the concrete shell that housed five coal combustion units.
The remaining transmission infrastructure could support hundreds of additional megawatts of battery storage and energy generation. Duke plans to bring 6,550 megawatts of battery storage online across its Carolinas service territories by 2035, according to its latest filings with state regulators.
Duke plans to construct another 167-megawatt battery to replace one of the former coal plant’s units. It would be the utility’s largest battery project to date.
“We are already considering additional battery storage on top of that, given the extensive infrastructure we have here,” Duke Energy spokesperson Bill Norton said, referring to the remaining transmission infrastructure that used to serve the coal plant.
The project came in under budget and ahead of schedule, thanks in part to federal tax credits. They helped make it cheaper for Duke to build at the former coal plant, with about $100 million invested in Gaston County.
Matching energy supply to demand
When Duke Energy plans new power plants, the utility looks at peak demand — the few hours each year when demand is highest. Battery storage can help bring that peak down, reducing the amount of new power Duke needs to supply.
For example, nuclear plants can produce excess energy generated at night, when residential and commercial customers use less power. Solar farms can produce surplus energy during the middle of the day, when the sun is high. A battery stores that extra energy for later use, such as late in the afternoon when workers return home and turn on appliances or charge electric vehicles as the sun sets.
Duke Energy’s Bill Norton said it will be particularly useful in the morning, helping to “fill that gap” before solar farms begin generating large amounts of electricity.
“When you're bundled up, get up in the morning, getting dressed, everyone's thermostats come on,” Norton said. “That's really when battery systems come to life.”
The batteries can recharge during the day with lower-cost solar energy, reducing the natural gas fuel costs Duke passes along to ratepayers. They can also receive energy from other electricity sources, including natural gas, coal and nuclear power.
Duke Energy currently operates 253 megawatts of energy storage in the Carolinas at nine sites, including the Allen location. The largest site is in Knightdale, north of Raleigh.
Duke will start building the next battery at the Allen plant site in May and aims to finish construction during the second half of 2027.
