On July 17, Nobelist and Academy Award winner Al Gore issued a stirring challenge to our nation to produce 100 percent of our electricity from renewable energy and carbon-free sources within 10 years. Gore asserted, "The quickest, cheapest and best way to start using all this renewable energy is in the production of electricity. In fact, we can start right now using solar power, wind power and geothermal power to make electricity for our homes and businesses." This massive push for no-carbon electricity production would help prevent climate change and cut our dependence on foreign oil. Of course, great-souled visionaries such as Gore do not concern themselves with piddling and mundane issues such as who will pay for this marvelous no-carbon energy future and how much it will cost. Not being burdened with a great soul, I decided to don my green eyeshade and make a preliminary stab at figuring out how much Gore's scheme might cost us.

According to the Energy Information Administration, the existing capacity of U.S. coal, gas, and oil generating plants totals around 850,000 megawatts. So how much would it cost to replace those facilities with solar electric power? Let's use the recent announcement of a 280-megawatt thermal solar power plant in Arizona for $1 billion as the starting point for an admittedly rough calculation. Combined with a molten salt heat storage systems, solar thermal might be able to provide base load power. Crunching the numbers (850,000 megawatts/280 megawatts x $1 billion) produces a total capital cost of just over $3 trillion over the next ten years.

What about wind power? Oilman T. Boone Pickens is building the world's biggest wind energy project with an installed capacity of 4,000 megawatts at a cost of $10 billion, or about $2.5 billion per 1,000 megawatts. For purposes of illustration, this implies a total cost of around $2.1 trillion over the next ten years to replace current carbon-emitting electricity generation capacity with wind power. That's assuming that the wind projects generate electricity at their rated capacity at or near 100 percent of the time. Making the heroic assumption that in fact wind projects will generate power at about one-third of their rated capacity (due to wind variability), this would imply tripling the number of wind power generators. This boosts the total overall cost to more than $6 trillion over the next ten years.

What's the potential for geothermal electricity generation? Geothermal power taps the heat of the Earth itself to make steam to drive turbines to generate electricity. For instance, superhot water erupting from the Geysers in northern California fuel power plants with a generation capacity of 725 megawatts. But such geothermal sites are relatively rare. However, an unconventional geothermal source—hot dry rocks—might supply us with no-carbon electricity. In lots of places, rocks several kilometers down are quite hot. To get at this heat, engineers drill at least two boreholes and inject cool water in one. The injected water flows around fractured hot rocks and rises through the other borehole as steam to drive a turbine to generate electricity. Some very preliminary figures suggest that it would cost around $3 billion for build a 1000 megawatt geothermal plant. Replacing 850 gigawatts of carbon-emitting power generation capacity with geothermal electricity would cost around $2.5 trillion over ten years.

Curiously, nowhere does the "N-word"—nuclear—appear in Gore's speech. Currently, 104 nuclear power plants generate about 20 percent of America's electricity. Once a nuclear plant is up and running, it is essentially carbon-free. Westinghouse claims that it can build a third generation 1,000 megawatt nuclear power plant for around $1.4 billion. Assuming this estimate is right, all U.S. carbon-emitting electricity generation plants could be replaced with nuclear power at a cost of about $1.2 trillion by 2018.

One other issue: Just how does using renewable sources of energy to generate electricity free us from dependence on foreign oil when only a tiny bit of crude is burned to produce electricity? The vast majority of petroleum is turned into transportation fuels, while home heating accounts for around two percent of total U.S. petroleum consumption. The answer, evidently, is a vehicle fleet powered by electricity. Although Gore doesn't dwell on it, he does mention that we should help "our struggling auto giants switch to the manufacture of plug-in electric cars."

In 2006, a U.S. Department of Energy study concluded that if 84 percent of all cars and light trucks were plug in hybrid electric vehicles (PHEVs), fueling them would not require any additional electric generation capacity. The study assumes that the PHEVs would travel an average of 33 miles per day solely on electric power and could be charged using off-peak power at night. PHEVs would cost between $6,000 and $10,000 more than conventional cars. Such a PHEV fleet could reduce oil consumption by 6.5 million barrels per day, or approximately 52 percent of our oil imports.

While the capital costs for current versions of renewable no-carbon electricity generation are high, one big advantage is that their fuel costs are low to non-existent. Gore is also probably right that the prices for renewable energy production technologies will fall in the future. However, his proposed crash program would put an immediate steep upward price pressure on the commodities—steel, concrete, silicon, copper—that go into building energy infrastructure. All of the rough calculations above are for generating capacity alone and do not include the costs of a $1 trillion smart grid upgrade for our creaky electric power distribution system. And does Gore plan to compensate the shareholders of conventional power generation companies when their assets are forcibly scrapped?

As a very rough low estimate, Gore's 10-year no-carbon energy plan would cost about $300 billion per year for the next ten years. According to the Brattle Group consultancy, "new and replacement generating plants will cost about $560 billon through 2030, absent a significant expansion of energy efficiency programs or new climate initiatives." That comes to an average of about $25 billion per year over the next 22 years. Gore's proposal is a "new climate initiative" that aims to spend twelve times more than the utility industry would otherwise annually invest in new and replacement generating capacity. Gore explicitly likens his scheme to NASA's Apollo program, but reaching the moon cost only $150 billion (in current dollars) spent over eight years. In other words, getting to the moon cost half of what Gore wants to spend annually to realize his no-carbon energy vision.

"Of course there are those who will tell us this can't be done," warned Gore. I am not one of those people. I am sure it can be done. But before embarking on his "generational challenge to re-power America," I would like the former vice-president to sketch out a few more details on how it's going to be paid for and who's going to be stuck with the bill. Without those answers, Gore's bold challenge amounts to little more than hot air.

Ronald Bailey is reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books.