The Electric Reliability Council of Texas (ERCOT), which oversees the grid for most of the state, said in an annual report that the state's power reserves -- the minimum capacity needed to cushion against extreme weather or unplanned outages -- may drop below 10 percent by 2014. A year ago, it said the reserve margin would remain above that level until 2018.

The worsening outlook comes one year after last summer's protracted heat wave and drought triggered record electricity demand in Texas, which forced ERCOT to declare emergencies on six hot days in August to avoid rolling power outages.

The operator has already warned that power resources will be tight this summer despite the return of some older natural gas-fired plants that will be needed to help keep lights and conditioners running.

Looking forward, while supplies will grow slowly, rising power demand may exceed supply by 2022, ERCOT said.

"To ensure future electric reliability in the ERCOT region, we need to take immediate steps to address this issue -- on both the supply side and the demand side of the resource adequacy equation," Trip Doggett, ERCOT's chief executive said in a statement.

ERCOT and state regulators are taking a number of steps to prepare the state for a hotter-than-normal summer again this year.

At best, the grid agency expects this summer's reserve margin to be 14 percent - slightly above the 13.75 percent target - with the return of several older gas plants.

In 2013, ERCOT expects a new coal plant to be operational, boosting the summer reserve margin to 14.3 percent. By 2014, however, the reserve margin may fall to 9.8 percent; then to 6.9 percent in 2015, and into negative territory by 2022, according to Tuesday's long-term report.