It’s not easy to convey the scale of the two initiatives Apple announced today to reduce its carbon footprint in China—Building 200 megawatts of solar projects in the provinces on its own and partnering with its Asian suppliers to install another 2 gigawatts of new clean energy.

Apple’s press release offered some helpful analogies.

—The 40 megawatts of solar projects already completed in the Sichuan Province produce more than the total amount of electricity used by all of Apple’s offices and retail stores in China.

—The 200 megawatts of solar projects planned for the northern, eastern and southern regions of China will produce enough energy to power 265,000 Chinese homes in a year

The combined programs will avoid over 20 million metric tons of greenhouse gas pollution in China between now and 2020, the equivalent of taking nearly 4 million passenger vehicles off the road for a year.

“Climate change is one of the great challenges of our time, and the time for action is now,” said Tim Cook, Apple’s CEO. “The transition to a new green economy requires innovation, ambition and purpose.”

It also takes a lot of money. Apple achieved 100% carbon neutrality in its U.S. operations in part by generating its own clean energy and in part by buying credits from other clean energy providers. Now it’s doing the same in China.

Not every company can afford that. Still, Apple is getting plaudits for leading by example.

“We need governments and companies to transition us to renewable energy as rapidly as possible,” said Gary Cook of Greenpeace, an organization that played Apple’s scold not that many years ago. “Apple’s announcement today is a major step forward in building a renewably powered supply chain for its products.”

Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple AAPL coverage at fortune.com/ped or subscribe via his RSS feed.

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