The average temperature in California has already increased by 1.7 degrees Fahrenheit over the last 100 years. The report says future summers could be even hotter and drier. On hot days, transmission lines lose 7 to 8 percent of electricity.
At the same time, people will use more electricity to cool their homes, says Bob Weisenmiller, chair of the California Energy Commission.
WEISENMILLER: "These reports indicate we could see up to an additional gigawatt power of demand in peak periods in ten years."
A gigawatt of electricity is enough to power about three-quarters of million homes.
Weisenmiller says one solution will be to develop more localized power sources. This can help cut transmission losses-- and it makes the power grid less vulnerable to interruption from forest fires.
Climate change is projected to bring more frequent and more intense forest fires. The report found this puts many of the state's power lines are at increased risk. The most vulnerable lines, including major ones in Los Angeles county and the northern half of the state, are 40 percent more likely to put out of service by fire.
Cal Fire Director Ken Pimlott, says hotter and drier summers are projected to bring fires that burn longer and cover more ground.
PIMLOTT: "Most disconcerting for us, I think, in the fire service community is the rapid increase in the number of large, damaging fires that have occurred in recent years. Of the 20 largest fires that have occurred in California, the most damaging fires, 11 of those have occurred since 2002."
Before that, Pimlott says there was only about one large damaging fire per decade. Among the solutions the state is considering is construction of more local power sources, which would mean less reliance on long transmission lines.