CHARLOTTE, N.C. (AP) — Duke Energy Carolinas asked North Carolina regulators Thursday to raise residential electricity rates by nearly 18% over three years as part of a broad request to raise revenues from its 2 million customers in the state.

Proceeds from the rate case initiated by the state Utilities Commission, the first undertaken by the Duke Energy subsidiary since 2019, would go in part to make electric grid reliability and security improvements and help it collect more power from renewable sources, the company said.

Duke Energy Carolinas’ coverage area spans much of central and western Carolina, including Charlotte, Durham and the Triad.

The rate case is similar to one filed in October by Duke Energy Progress, which covers customers in eastern and central North Carolina — including those in Raleigh, Fayetteville and Wilmington — as well as in and near Asheville. Both companies are subsidiaries of Charlotte-based Duke Energy Corp.

Thursday’s proposal, with annual increases in early 2024, 2025 and 2026, would result in overall cumulative rate increases of 15.7% and 17.9% for residential customers. A typical Duke Energy Carolinas residential customer would see their monthly bills rise from $115.01 per month to $127.55 starting next Jan. 1, with smaller increases in successive years to $134.63, according to a news release.

The proposal would result in over $820 million in additional net retail revenues by 2026, according to figures from the utility.

As with the Duke Energy Progress case, Thursday’s proposal also includes a new program for low-income customers to reduce their bills and new energy efficiency programs offered to all customers that can lead to savings on bills.

The utility commission, with its seven members chosen by the governor, decides whether to approve or modify rate requests after holding a hearing and receiving comments from advocacy groups, customers and the commission’s public staff.

The rate requests come after Duke Energy substations in central North Carolina were damaged by gunfire in early December, knocking out power to 45,000 customers in Moore County. And hundreds of thousands of customers of the two subsidiaries in North and South Carolina were subjected to rolling blackouts on Dec. 24 during freezing weather as power demand soared but supply dwindled.