Tiring of its mission to "organize the world's information," Google has set itself a new objective: save the planet.

The search giant unveiled a US$4.4 trillion plan Wednesday to reduce the U.S.'s dependency on fossil fuels and embrace alternative energy. The proposal would yield a net saving of $1 trillion by 2030 and slash U.S. carbon dioxide emissions by 48 percent, according to Google, which said it had been busy "crunching the numbers."

The plan involves weaning the U.S. off of coal for producing its electricity and turning to wind, solar and geothermal power instead. It would also cut oil use in cars by 40 percent and use electricity for personal transportation. Google said its goal in announcing the plan, called Clean Energy 2030, was to stimulate debate.

"With a new Administration and Congress -- and multiple energy-related imperatives -- this is an opportune, perhaps unprecedented, moment to move from plan to action," the company said.

It's the latest and perhaps most ambitious attempt by Google to shape public policy. The company has already weighed in on issues like worker immigration, intellectual property law and net neutrality. Energy is further from its expertise, but Google has been hiring experts to help with the task, including the lead author of the proposal, Jeffery Greenblatt, a former scientist with the Environmental Defense Fund.

CEO Eric Schmidt was to present the proposal in San Francisco on Wednesday evening. Google also described the plan in a blog posting and in more depth on its Wikipedia-like Knol Web site.

It deals primarily with two areas -- electricity production and personal vehicles. The basics look like this:

Reduce energy use today: Naturally for Google, it starts with computers. Data centers and personal computers both can be operated much more efficiently, by unplugging PCs when they are not in use, for example. Building codes can be more aggressive, and "smart meters" in homes that give real-time pricing should encourage people to use less power. Pacific Gas & Electric is already installing such meters in northern California.

Electricity: The U.S. today produces half its electricity from coal, 20 percent each from natural gas and nuclear energy, and 1.5 percent from oil. The plan would replace coal and oil with primarily wind, solar and geothermal energy (using heat from inside the earth). It calls for keeping electricity demand at today's level, which would lop 30 percent off the projected demand in 2030. Onshore and offshore wind would account for a further 29 percent of demand, solar 12 percent and geothermal 15 percent. Nuclear, hydro and natural gas would make up the rest.

Google acknowleged that solar energy is expensive today, but said the deserts in the southwest could be used for "concentrating solar power," which could "bring costs down fast." Geothermal energy is "the sleeping giant," according to Google.

Personal vehicles: The U.S. consumes 21 million barrels of liquid fuels per day, with 60 percent going into cars and other "light personal vehicles." The plan calls for incentives to increase electric and hybrid car sales to 100,000 in 2010 (annual U.S. car sales today are about 15 million), 3.7 million in 2020 and 22 million in 2030. It proposes boosting gas mileage for conventional vehicles to 45 miles per gallon, something experts say is plausible.

Economics: Google made several assumptions about costs and savings, including the costs of alternative energy equipment, such as the infrastructure for charging electric cars, and the savings from more efficient power sources. It assumed that gasoline will double in price to $8 per gallon by 2030, and accepted that fluctuations could add or remove billions in its calculations.

Jobs: It predicted that millions of jobs in construction, operations and professional services would be created with the alternative energy industries, as well as more jobs in electric vehicle manufacture.

Google isn't the first to devise such a plan. It acknowleged that Former Vice President Al Gore has come up with a more ambitious proposal. It remains to be seen now if Google's effort will stir the U.S. into action.