The polar vortex that sent U.S. temperatures plunging last week has lifted. But what did we learn from the record-breaking cold snap that killed more than two dozen people and sent hundreds to the hospital with frostbite and other weather-related injuries?

The only real defense against Winter Storm Jayden was fossil fuels. Even as U.S. Rep. Alexandria Ocasio-Cortez and U.S. Sen. Ed Markey (Democrats from New York and Massachusetts, respectively) prepare to unveil the details of the “Green New Deal,” we know that the inexpensive, concentrated energy from fossil fuels—not cheerful talk about the promise of renewable energy—saved lives and warmed hearths.

Let’s take two states as examples.

In Michigan, a 99-year-old record was broken in that state as the city of Ironwood (in the Upper Peninsula) saw a low of minus 26 degrees Fahrenheit. Yet on Wednesday, Michigan Gov. Gretchen Whitmer asked Michiganders to lower their home and work thermostats to 65 or below—to help ensure there was enough natural gas for everyone.

That’s a little curious, because Michigan has vast natural gas reserves—the Antrim gas field in the Lower Peninsula—and more natural gas storage capacity than anywhere else in the U.S. Only 8 percent of the state’s energy comes from renewables. Yet state officials are calling on utilities to phase out non-renewable energy sources on a tighter and tighter schedule.

Charlotte Jameson, of the Michigan Environmental Council, claimed last fall that “Transition to 100 percent clean, renewable energy is achievable and will usher in more economic prosperity for the state while reducing costs for families and protecting public health and the environment.”

None of that is true. Solar and wind power are inherently sporadic and unreliable, and must be backed up with traditional sources of power—fossil fuels or nuclear. And far from ushering in economic prosperity, Michigan’s proposed renewable energy standard will come at great cost to taxpayers and ratepayers, in the form of higher electricity prices and taxpayer-funded subsidies for renewable energy projects.

Records were broken in Indiana, as well. That state saw not only low temperatures, but also “frost quakes” as groundwater froze and expanded.

Yet in Indiana, too, renewable energy was largely a no-show. Wind produces just 5 percent of the state’s power, and solar less than 1 percent.

Yet the cold, hard facts are difficult to ignore in weather like we saw last week.

Government can’t mandate the advances in storage capacity and wind and solar efficiency we’ll need to reach the goals laid out in renewable energy standards. What government can do—by imposing strict rules that lead to the premature closing of reliable fossil fuel-powered generators—is drive up the cost of electricity (New Yorkers, for example, pay about 45 percent more per kilowatt hour than the national average, largely because of regulations and mandates).

Which brings us to that Green New Deal, which would double down on the policies that are making power more expensive—and less reliable—in many parts of the U.S. Details are scarce, but we are starting to get an idea of just what that legislation will entail.

It’s very likely to be President Obama’s Clean Power Plan Redux, with a little social justice thrown in (Rep. Ocasio-Cortez likes to talk about income inequality and higher taxes on the rich when she discusses it).

Yet Harry C. Alford, of the National Black Chamber of Commerce, warned that the Clean Power Plan (even without higher taxes) would have increased poverty among blacks by 23 percent and Hispanics by 26 percent, due to “severe and disproportionate economic burdens.” That’s because lower-income families spend a larger portion of their income on electricity and transportation fuel, not to mention food, clothing and housing, which are also affected by energy pricing).

Winter Storm Jayden should have awakened us to some cold truths. Today, fossil fuels stand between us and the icy chill of winter weather. Policies that try to chase them from our energy portfolios prematurely are doomed to fail—and to leave American families, particularly the poorest among us, out in the bitter cold.