Following in the footsteps of Apple and Google, health care giant Kaiser Permanente will announce on Wednesday agreements to buy enough renewable power to provide half the electricity used by its hospitals, clinics and offices in California.

Kaiser, based in Oakland, will buy electricity from both a massive solar power plant under development in Riverside County and a portion of the Altamont Pass wind farm, soon to be refurbished with new turbines. In addition, the company plans to install solar arrays on as many as 170 of its hospitals and other buildings throughout the state.

The initiative will cost Kaiser about $35 million per year in power-purchase agreements. But considering California’s high utility rates and the likelihood of future rate increases, Kaiser expects the plan to break even or save money in the long run.

Last week, Apple reported plans to help fund construction of a solar power plant in Monterey County and use the electricity at the company’s sprawling California operations. And Google, which has invested more than $1.5 billion in renewable power projects worldwide, said it would buy wind energy from the Altamont Pass.

All three companies cast the shift to renewable energy as a necessary step to fight climate change. Kaiser in 2012 pledged to cut its greenhouse gas emissions 30 percent by 2020. The agreements announced Wednesday should help the health care company, which serves 9.6 million people, reach its goal three years early.

“Climate change isn’t a distant threat,” said Kathy Gerwig, Kaiser’s environmental stewardship officer. “The health impacts of a changing climate can be felt today in the form of increasing rates of asthma and respiratory ailments, spread of infectious diseases, heat stress and injuries from severe weather events.”

Almost half of the electricity will come from a single facility — the Blythe Solar Power Project, under development in the Southern California desert.

Kaiser has entered into a 20-year contract with the project’s owner, NextEra Energy Resources, to buy 110 megawatts of electricity from the power plant, starting in 2016. A megawatt is a snapshot figure, roughly equal to the amount of electricity used by 750 typical homes at any given moment.

NextEra also owns a portion of the Altamont Pass wind farm, one of the nation’s oldest, and plans to replace some of its aging turbines with newer, more efficient models. Kaiser has reached a long-term agreement for 43 megawatts of electricity from NextEra’s Altamont facility, which will supply power to Google as well.

Finally, Kaiser will partner with NRG Energy to install enough solar arrays on its hospitals and corporate campuses to generate as much as 70 megwatts of electricity. NRG will build, own and operate the solar arrays, selling the electricity to Kaiser at a fixed cost under a 20-year contract.

David R. Baker is a San Francisco Chronicle staff writer. E-mail: dbaker@sfchronicle.com Twitter: @DavidBakerSF