Washington State has so much renewable energy that during storms when both their hydro-power and their wind power is producing maximum power, they have to shut down all of the fossil fuel plants or the excess power will result in a blackout.
During the "June 2010 emergency, when a severe storm whipped through the region. The transmission network had so much power that the agency turned off all its fossil fuel generation, gave electricity away to neighboring networks and even told the system's only nuclear plant to slash its production by 78 percent, a highly unusual step. "
http://www.nytimes.com/2011/11/05/busine...To store excess power temporarily the utilities are providing 100 Gallon water heaters and electric heaters to heat ceramic bricks which can store the heat until it can be used later.
Now a solution to the problem of excess energy might be coming from Texas. They have built a huge 4 megawatt Sodium Sulfur battery. environmental costs, so power companies expect an exponential increase in battery use within 5 years.
http://www.power-technology.com/features...Texas is using the battery to solve distribution problems but the same type of battery has now been made smaller and perfected so it is safe enough to put inside a single family home's basement.
Paired with the increasingly inexpensive and more efficient photovoltaic solar panels, the system could provide homeowners with 100% of their power. But when hooked up to a utility systems power grid, it could also provide storage for the utility to prevent blackouts and brownouts.
http://solar.calfinder.com/blog/products...The traditional energy companies have always said that renewable energy was not practical because solar and wind are not constant. Now with battery storage there may be less justification for dirty fossil fuel or dangerous nuclear power.
Soon there may be no excuse for not covering all of the rooftops, wherever it is sunny, with solar panels, especially since air conditioner use is higher just when the maximum solar power is being generated.