The long-lasting, severe drought affecting California is likely to have major ramifications for how the region generates electricity this summer, as well as how reliable and costly that supply is, according to a new report from the U.S. Energy Information Administration.

Driving the news: The drought's depletion of California's large reservoirs is likely to strain hydroelectric plants to the point where some may have to be shut down.

• Lake Shasta, the state's largest reservoir, has only seen one other year when the reservoir storage was lower than it is now, the EIA found.
• The cut in hydropower, which typically supplies about 15% of California's summer electricity generation, will place more of a burden on natural gas plants and increase electricity rates and greenhouse gas emissions, per EIA.

Threat level: There are concerns that nearby states won't be able to make up for California's shortfalls as they cope with their own hotter than average summer, which the National Weather Service is calling for across the West.

The big picture: As the Southwest grapples with a megadrought, driven in large part by human-caused climate change, the region's electricity mix is rapidly shifting.

• More solar and wind power is coming online, as fossil fuel plants are shut down in an effort to cut greenhouse gas emissions.
• While the water storage picture this year looks similar to 2015, the EIA finds that California's energy mix has changed significantly since then.

By the numbers: According to the report, 58% of the state's natural gas units have been retired since 2015, amounting to 6,500 megawatts of generating capacity.

• At the same time, solar capacity has increased by 8,800 megawatts, and the state has deployed more battery storage.
• Still, there may be shortfalls between power demand and electricity supply, which the state makes up for by importing power from its neighbors. However, the other states will also see strained power supplies due to drought, particularly Nevada and Arizona.

Meanwhile, a recent report from the North American Electric Reliability Corporation, whose mission is to monitor the grid and reduce reliability risks, found that there is an "elevated" danger of power disruptions in the West this summer due to the combined impacts of heat and drought.

• Wildfires will cause additional challenges, the report found, from threatening interstate transmission lines to sending so much smoke into the sky that it reduces the output from solar installations.
• The report also found that any extreme heat events, particularly widespread heat waves such as occurred in the Pacific Northwest in 2019, will put large regions at risk of energy emergencies due to less power being available to transfer from one state to the next.

The bottom line: California is facing the simultaneous consequences of the effects of climate change, including heat waves, wildfires and drought, along with growing pains from the bumpy integration of climate solutions, such as solar and wind power plants, into the broader grid.