Renewable energy production in Texas rose 12 percent last year, according to the state's grid operator.

The report by the Electric Reliability Council of Texas found that power generators participating in the state's renewable energy credit trading program produced 38.1 million megawatt-hours of renewable energy last year. That's up from 33.9 million in 2012.

One megawatt-hour would show up on an electric bill as 1,000 kilowatt hours, and is about the amount many residences use in a month.

Almost all of that production - 97 percent - came from wind power. The remaining renewable power sources included landfill gas, hydropower, biomass energy and solar power.

The findings were part of an annual filing ERCOT makes to the Public Utility Commission of Texas.

State standards require the state's electricity market to use a certain amount of renewable energy, and power providers must acquire renewable energy credits, which can be traded, to meet those mandates.

Natural gas and coal remain the state's dominant power generation fuels.

Last year wind provided 9.9 percent of energy consumed on the ERCOT grid, although the share can approach 30 percent on windy days.

Other renewables produced a fraction of a percent.