Duke said its original proposal would have increased rates for residential customers by 6 percent in 2009 and 2 percent in 2010 and decreased rates by 2 percent in 2011.
The increase will be 2 percent annually for 2009 through 2011 for Duke's non-residential customers, the utility said.
The rates cover the company's basic generation costs, Duke said. Customers' bills will also include Duke's costs for fuel, environmental rules compliance, and electricity bought from other systems to meet peak demands.
Duke also agreed to invest $1.75 million per year in assistance to low-income customers, consumer advocates said. The money will be distributed by local nonprofit organizations.