Georgia Power customers, your bill is going up in April.

Residential customers will see an average 1.7 percent increase -- about $2.46 -- for a typical monthly bill. State utility regulators approved the increase in 2010, part of a three-time adjustment that also guaranteed the utility a 11.15 percent profit.

The first increase, along with a fee for the Plant Vogtle expansion, kicked in January 2010, adding about $14.50 a month to typical bill. After the April increase, the third hike will come in January 2013.

The company agreed to phase in the rate increases to "minimize impact on customers' bills," Georgia Power spokeswoman Lynn Wallace said.

"At a time when consumers are more cash-strapped than they have been in decades, these increases are especially hard-hitting," said Clare McGuire, Georgia Watch's senior counsel and consumer energy program director.

The rate increase covers $122.3 million that will help pay for two natural gas units that Georgia Power has built at Plant McDonough. The January 2013 rate hike will cover a third combined-cycle natural gas unit.

Georgia Power hasn't determined how much that January rate increase will be. The utility must file that information with the Georgia Public Service Commission 60 days before the increase is scheduled to show up on customer bills.

Georgia Power is making several changes at Plant McDonough to comply with state environmental rules. The utility could close old units, retrofit them with pollution controls or convert them to run on natural gas. Georgia Power closed one of two units there in September 2011 and the other last month.

The new natural gas units will generate 2,500 megawatts of electricity, enough energy to power approximately 625,000 homes, Wallace said.

Additional rate increases could follow as Georgia Power starts making changes at other coal-fired plants to comply with federal environmental rules. Georgia Power's parent, Atlanta-based Southern Co., has warned that complying with the new rules could cost between $13 billion and $18 billion by 2020, driving up electricity bills by another 10 percent to 20 percent over several years.