Duke Energy’s new plan uses home batteries to feed power back to the grid | WFAE 90.7

Duke Energy customers can now save money on their electric bills while also contributing power from their home batteries to the grid. A new battery audit program gives Duke permission to draw power from home batteries during periods of high demand.

“This program ensures that we get battery power at the precise times the grid needs it,” said Brian Lusher, Duke Energy product and services manager.

In return, battery owners receive a refund on their monthly utility bills. The amount of money customers get back will depend on their battery.

“We decided to pay the customer based on the value a specific battery model would provide to the system,” Lusher said.

Duke Energy predicts that North Carolina will experience unprecedented growth in energy demand over the next decade, fueled by a growing population and economy. Meanwhile, the state aims to become carbon neutral by 2050, eliminating climate-warming fossil fuel emissions. One strategy to meet future energy needs is to make homes more energy efficient and manage when homes draw power from the grid.

Lusher says this new initiative is a way to achieve that goal by encouraging customers to use batteries — and allowing Duke to use that power during periods of high demand when shale gas generators are fired up.

For example, afternoon heat in summer lingers even as the sun sets and solar generation declines. Customers tend to turn on air conditioners when they get home from work, straining the grid at a time when there is less renewable energy available.

To balance this, a home battery could charge during the day and discharge in the late afternoon when the sun is lower, spreading out energy demand.

Current batteries can store enough energy to balance a home, making it virtually invisible on the grid. As batteries improve, Lusher predicts that power from home batteries will extend a bit further while remaining local.

“If you’re the only customer on your street that has a battery, that energy doesn’t leave your street,” Lusher said.

About 9% of Duke Energy solar customers have installed a home battery. Not every battery connects to a solar system—some homeowners purchase batteries instead of a gas-powered generator to power their homes when needed. For homes covered by the battery inspection program, Duke will not discharge batteries below 20%.

Duke Energy projects that enrollment in battery-control programs will make about 5 megawatts available to grid operators by the end of the first full calendar year—enough to power about 1,200 homes. That may not sound like much when compared to one of Duke’s proposed gas turbines, which typically deliver 450 megawatts of power, but the benefits go beyond those energy savings.

Battery control reduces energy losses due to transmission, reduces residential energy demand during periods of high demand, and increases the share of renewable energy in the state’s energy mix. In short, battery control reduces fracked gas generator run time.

Duke Energy expects about 700 people to sign up in the first year, but that is not the upper limit.

“There is no upper limit to how many of these programs we can offer at this point because we are committed to acquiring customers,” Lusher said.