Hillary Clinton has a new plan to ramp up emissions-free renewable energy. That puts her head-and-shoulders above her GOP rivals, who range from climate chickens to climate deniers. Nevertheless, her plan is plainly worse than what she ran on eight years ago — and it has a glaring gap.

Clinton’s proposal came under immediate scrutiny in part because she hasn’t taken a strong stand on the controversial Keystone XL oil pipeline since leaving the State Department. But, like the rest of the debate on the pipeline, this reaction misses the point. The fate of the planet does not depend on a single oil infrastructure project but on the high-level policy that will shape the market for clean energy. On this, Clinton has some ideas; the problem is that they are all second-best ideas.

Clinton’s strategy begins with a pledge to defend President Obama’s greenhouse-gas regulations, the final version of which will emerge soon from the Environmental Protection Agency. Those underpin Obama’s promise to world leaders that the U.S. will reduce its greenhouse emissions by 26 percent to 28 percent by 2025 and increase renewables to 20 percent of the power grid by 2030. Clinton would enhance that commitment, promising that a full third of U.S. electricity would come from renewables by 2027, with an emphasis on installing new solar panels.

To get there, Clinton would put up federal cash to spur competition among states to reduce emissions, a concept that resembles Obama’s Race to the Top education initiative. She would invest in more energy research and development. She would also use the tax code to subsidize investment in or electricity production from renewable energy sources, extending and reforming the renewables tax subsidies already on the books.

Yet it’s curious that Clinton didn’t offer a specific commitment to reducing greenhouse-gas emissions, as she did in her previous White House run, preferring instead to articulate a renewables goal. Emissions are what drive climate change; renewables are just one tool to reduce them. Others could include nuclear power or careful use of natural gas in the medium term. What matters is not how the country slashes its emissions but that it does so — and as cheaply as possible.

The best translation of that principle into policy is simple: Get rid of the country’s complex web of energy subsidies and replace it with a price on carbon dioxide emissions. This wouldn’t tilt the playing field, as some erroneously allege. It would flatten it, forcing emitters to pay for the dangerous damage they do to the environment. Market behavior would therefore become much more rational: Businesses and consumers would use electricity more carefully; the market appeal of low-carbon energy technologies would reflect their real value; government planners would have less influence over the country’s energy future.

The drawbacks are all political. The term “carbon tax” doesn’t play well. “Cap and trade” has been smeared. Yet Clinton favored a cap-and-trade plan in 2007, and the case for carbon pricing has grown only stronger since then. Giving the policy its due would hardly be the most politically unrealistic campaign proposal a candidate has offered. Yet it would be among the most reasonable.

Clinton grandee John Podesta assures that “these proposals are only the first steps in an ambitious climate and energy strategy.” We hope so.