It is too early to judge the final outcome of the nuclear crisis that continues to unfold in Japan. It is already clear, though, that people around the world are taking a second look at nuclear power. Germany has moved quickly to shutter several plants at least temporarily, while China has announced a pause so that it can revamp regulations. The disaster’s ultimate effect on American energy policy is uncertain, but it’s entirely possible that it will cause Congress to make significant adjustments. What would backpedaling on nuclear power mean for the United States?

The United States is home to 104 nuclear reactors that currently provide 20 percent of our electricity. No new reactors have broken ground in decades, but interest from utilities has ticked up, with several proposing new plants in recent years. To what degree the interest will translate into real, functioning plants is still uncertain: As of last year, the Department of Energy projected that only six plants would come online by 2035, primarily because of high costs.

A domestic backlash against nuclear power could stall these projects indefinitely. Some skeptical policymakers would also like to retire our older (and, they worry, riskier) plants. If regulators require all plants to shut down after 60 years in operation, analysts predict that U.S. nuclear generation in 2035 would be one-third lower than what it would have been otherwise; more draconian measures would result in steeper declines unless replacement plants were built. (If, on the other hand, policymakers decided to boost nuclear power with the loan guarantees, subsidies, or broad-based climate rules that have been much debated in recent years, nuclear generation could more than double.) What would one-third less nuclear energy mean for Americans?

A couple of things it won’t do: significantly increase electricity prices or dependence on imported oil. New nuclear development doesn’t make electricity cheaper, since nuclear power plants tend to be expensive to build. Closing existing plants might be more consequential, since once a plant’s capital expenses have been paid off, the cost of generating power tends to be low. (Think of it like owning a home: It’s a lot cheaper once you’ve paid off your mortgage.) But according to a Department of Energy analysis last year, shutting down every nuclear plant after 60 years of operation would increase projected electricity prices a mere 4 percent over the next 25 years. So long as the United States does not take precipitous steps, a move away from nuclear would probably be manageable.

Nor would increasing nuclear power significantly reduce U.S. reliance on imported oil. Nuclear power displaces other sources of electricity, like coal and gas; it doesn’t replace oil. Some will argue that electric vehicles can allow nuclear power to replace oil in the transportation system. But the key to that is a cheap electric car, not an expansion of nuclear power. Once electric cars start getting widely adopted, they’ll displace oil regardless of where they get their electricity.

Marginalizing nuclear power would, however, throw a wrench into climate-change policy. Nuclear reactors might not seem the most eco-friendly power source after the Fukushima disaster, but they’ve been crucial to plans for curbing greenhouse-gas emissions. Nuclear power generation would have increased 74 percent by 2030 under the ill-fated Waxman-Markey climate bill, filling the gap left by climate-affronting coal plants, according to Department of Energy projections; the Environmental Protection Agency estimated a 50 percent rise. (Those projections are highly uncertain and much contested, but they provide a sense of where the U.S. government thinks things might head.)

The Waxman-Markey legislation, of course, is dead. Yet it still provides a useful guide to what might be required of a serious emission-cutting effort. In particular, the Clean Energy Standard that the President Obama announced in this year’s State of the Union address also seems to have been designed with a significant role for nuclear power in mind. (Details of the CES are sketchy, but the administration’s proposals appear to encourage shifts in the power sector similar to the aborted cap-and-trade bills.)

Could other low-carbon alternatives take the place of nuclear power? The EPA attempted to answer this question by modeling a scenario in which the level of future nuclear generation is just a smidge higher than it is today. It then asked what other sources would have to step in for the U.S. to meet its emissions-cutting targets. Renewable energy replaced just a sliver of the lost nuclear generation—in large part because these renewables can’t provide “baseload” electricity without new technologies to store their intermittent power. Coal with carbon capture and sequestration stepped in to replace about a quarter, but that assumed significant advances on cost and technology. Natural gas became the most important alternative, making up about 70 percent of the lost nuclear power.

Gas looks to be critical to cutting emissions, but counting on it too much is problematic. Future supplies of cheap gas are far from guaranteed, particularly given local and environmental opposition to “fracking” and other approaches to developing unconventional gas resources. Even if those supplies materialize, using more gas for the power system will leave less for industry, transportation, and possible export. And even if plentiful gas remains available, carbon emissions from gas-fired power would become a problem a couple decades from now, when serious climate policy eventually requires utilities to switch to genuinely zero-carbon sources. Unless gas plants are able to capture and store their substantial emissions by then, they’ll eventually become a poor replacement for nuclear.

All of this might lead policymakers to some unusual conclusions. Republicans, the traditional supporters of nuclear, could think about throwing it overboard: Nuclear power does not actually do much to advance their oft-stated objectives of cheap electricity and independence from foreign oil. Democrats, typically more wary of nuclear, might resist attempts to close existing plants or block new ones—lest their climate-change goals get too far out of reach. Ultimately, skeptical environmental advocates may have to choose between the devil they know and a technological prayer.