The Electric Reliability Council of Texas is becoming less concerned about the prospect of tight electricity supplies as power companies build more natural gas-fired plants.

ERCOT, which operates the Texas power grid, said Friday the state should have plenty of power for the next four years. That's different from ERCOT's December assessment, that strong demand would strain supply.

ERCOT predicts the reserve margin, or percentage of excess capacity to make power, will remain above the 12.5 percent target until 2013. Last year, ERCOT said it would drop below the target in 2009.

The council said power generators are planning enough new plants to buoy the reserve margin to a comfortable level in the next five years.

What's changed? Power generators finished building six power plants this year. A potential downside, however: Those plants run on natural gas, the most expensive fuel for power generation.

Many companies favor building natural gas plants because they don't pollute as much as coal plants and are less vulnerable to potential carbon dioxide regulation. They also can build natural gas plants much more quickly than coal or nuclear plants.

ERCOT also predicts demand for power in Texas won't grow as quickly as it originally thought, because of the economic downturn.

The company also included energy conservation in this year's forecast. ERCOT trimmed 143 megawatts off of its load forecast this year to account for energy efficiency programs. That puts summer peak demand at 63,725 megawatts.