Avista Corp. reported improved first-quarter earnings, citing revenue growth from higher electric and natural gas rates, as well as growth in the number of customers the utility serves.

Avista reported net income of $31 million, or 57 cents per share, compared to net income of $25.2 million, or 47 cents per share, during the first quarter of 2008. The results were released Wednesday.

“Even with the decline in the economy, we saw approximately 1 percent growth in both electric and natural gas customers during the first quarter of 2009 as compared to first quarter of 2008,” Scott Morris, Avista’s chairman, president and CEO, said in a statement.

Higher rates approved by public utilities commissions in Washington and Idaho also helped the Spokane-based utility’s bottom line, he said.

Morris said other first-quarter highlights included:

•Better hydroelectric generation. Based on current snowpack conditions and projected stream flows, hydropower generation should be near normal for 2009.

•Falling wholesale prices for natural gas. The company expects to pass on savings to Idaho and Washington customers this year. Avista will file a formal request with Idaho and Washington public utility commission in the coming weeks.

•Advantage IQ, an Avista subsidiary, signed new contracts that should result in more than $2 million in new revenue. Advantage IQ helps companies manage their utility expenses.