Wind power is supposed to be a big part of the nation's energy future, and yet there are numerous idle windmills.

But a new turbine-renewal project is underway. In the Montezuma Hills, Enxco is planning to replace 255 idle windmills with 50 new turbines.

"We're capable of generating four times more electricity than what's existing out here," said Hanson Wood of Enxco Wind Farms.

The 23-megawatt site will soon produce 100 megawatts of clean, green, more-reliable energy -- enough for 50,000 homes.

But, as with all renewable power sources, though the wind and sunlight is free, there are problems.

Many wind turbines in the Altamont Pass are idled to protect a bird species that get hit by the turbine blades.

Some of the turbines are down for maintenance. And then there's the turbine's dependence on Mother Nature.

"If the wind doesn't show up, we have to make up for that electricity or the lights go out," said Stephanie McCorkle, California Power Grid operator.

When the sun isn't shining, solar is inefficient or non-existent. "There's not gonna be one solution, one silver bullet for our energy dependence," Wood said. "It's gonna come from multiple solutions like wind power, solar power and geothermal."

In other words, to keep the power grid reliable and instantly available, natural gas and nuclear power plants are essential to jump in when the wind stops blowing or the sun stops shining.

"Already on the grid, we're seeing the disappearance of 800 megawatts of wind power in an hour," McCorkle said. "That's a large power plant that was forecast to be there."

The more renewables put online, the more they are subject to radical swings in their ability to supply reliable power.

To maintain reliability, both PG&E and the state power grid have completely modernized their control centers so they can better predict where and when renewable power will or will not be available.