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An electricity meter is installed in a home in this file photo.

Starting Jan. 1, typical residential gas and electric customers of Pacific Gas and Electric Co. can expect their monthly bills to rise by $3.38, or about 2.8 percent, the San Francisco-based utility announced Tuesday.

The state-approved increases are intended to pay for higher energy purchasing costs combined with expenses associated with maintaining and modernizing a system that serves 15 million people in Northern and Southern California.

PG&E said its average residential electric rates will increase by 0.6 percent, or 23 cents for the typical customer. That's based on the use of 500 kilowatt hours per month, which the utility said is its systemwide average. The bills of residential customers who use 700 kilowatt hours per month will rise by 0.8 percent, or $1.16.

For the typical residential natural gas customer using an average of 37 therms per month, bills will rise by $3.15, or 7.3 percent, PG&E said.