Homeowners tend to start renovations hoping to make their houses greener and more energy efficient, if only for reasons of parsimony. They quickly discover that what they lightheartedly imagined to be a few minor upgrades are in fact massive expenses. All they wanted was energy-efficient windows, better insulation, a tankless water heater, a radiant system to replace their (dry, noisy, inefficient) HVAC and . . . dear God, did the contractor misplace a decimal point? We’re updating a modest row house, not building Versailles!

Ceilings and walls must be removed, then replaced; fancy new equipment installed; ductwork rerouted; slabs perhaps broken and repoured; ancillary systems brought up to modern housing codes. Much labor is required; much homeowner patience and cash, too. And the older the building, the more expensive and disruptive the process, since decades of obsolete junk have to be ripped out, with all appropriate environmental remediation measures taken along the way.

Yet Ocasio-Cortez, or someone in her office, apparently thought those repairs could be made to every building in the United States within a decade. And this is only one of the minor details of the plan; it barely merits more than a mention.

Much of the FAQ is devoted to the showier stuff, the policy equivalent of gold plumbing fixtures and Calacatta marble walls: replacing air travel with high-speed rail; junking every automobile with an internal-combustion engine; making affordable public transportation available to every single American (presumably including those who live hours from the nearest town?); replacing the electric grid with something smarter; meeting “100% of power demand through clean and renewable energy sources”; and — I swear I’m not making this up — providing economic security to people who are “unwilling to work.” This, too, is supposed to happen within only a decade, or thereabouts.

Going by my experience at energy-efficiencizing, I’d estimate that the Ocasio-Cortez plan would require the entire population of the United States — or at least those who aren’t “unwilling to work” — to drop whatever they’re doing and start training to become insulation installers, HVAC technicians, electricians, automotive engineers or demolition experts. But even a quarter of that effort doesn’t really seem very practical. Nor politically enticing. The only historical operation even approaching such scale was the U.S. mobilization for World War II, and unfortunately for Green New Dealers, the coal industry probably won’t cooperate by bombing Pearl Harbor.

The FAQ now seems to have been taken down, and the actual measure introduced to Congress was slightly less exuberant. Notably, it makes a nod to the need for technological and economic feasibility. But it’s still rather breathtaking. If Obamacare’s architects had suggested that their plan included finding a universal cancer cure within 10 years, at a cost of only 15 cents a dose, you’d kind of wonder about the people who drafted it.

But arguably Ocasio-Cortez’s team wasn’t really trying to put together a practical document. Rather, it articulates an ideal, one that we may never reach but should at least strive for. And there’s something appealing about that argument, because climate change is a pressing concern, and even if it weren’t, there would be ample reasons to want to obtain as much energy as possible from renewable sources.

Progressives frequently argue that getting to “as much as possible” requires setting goals that are out of reach. They call it “shifting the Overton window,” or widening the spectrum of plausible policy options, an idea broached in the 1990s by policy analyst Joseph P. Overton. The folk version: Ask for the stars, you’ll get the moon.

Fair enough. Sometimes people and causes do lose out by being too timid. What the progressive window-shoppers forget is that they can also lose out by being over-aggressive.

A pedestrian example: Many people could do better, salary-wise, if they simply negotiated harder with potential employers. But few of them could do better by opening with a pugnacious demand for $1 million a year. Wild demands, unmoored from reality, don’t increase what you ultimately take away from a negotiation; they are much more likely to end the negotiation abruptly when the other party concludes that you’re crazy.

The Green New Deal is nice vision of where the United States might try to go someday. But as an actual blueprint for the immediate future, it’s lunatic. And no matter how technically or morally sound your goals may be, as an opening political message, “We’re nuts!” is neither efficient, nor state-of-the-art.

Twitter: @asymmetricinfo