If Democrats pick their 2020 nominee based on how much cash they’d spend, Bernie Sanders’s got the primary sewn up.

On Thursday, the Vermont senator unveiled his version of the Green New Deal to combat climate change. Price tag: $16.3 trillion. That’s right, trillion — with a “t.”

That kind of number makes fellow Dems look like pikers. Joe Biden, for example, would only devote $1.7 trillion over 10 years for climate change. Miserly Elizabeth Warren has proposed a “paltry” $2 trillion.

Fact is, no other hopeful comes even close to Bernie’s eye-popping, all-in, 14-figure mega-tab.

Just how much money are we talking about? Consider that the entire federal budget is less than $4 trillion; Bernie’s Green New Deal would be more than four times that. That sure is a Green New Deal.

Where would the money come from? Not to worry, says Sanders. The plan would “pay for itself over the next 15 years.”

He sees evil billionaires and large corporations footing the bill through new taxes, fees and penalties. If not, of course, there’s always fairy dust.

The money would go to convert the nation to “100 percent renewable energy for electricity and transportation by no later than 2030.” It would also ensure “complete decarbonization” (whatever that is) “by 2050, at the latest.”

There’s cash, too, for all those who’d lose their jobs in the fossil-fuel industry: For “every displaced worker,” vows Sanders, “we will provide five years of a wage guarantee, housing assistance, job training, health care [and] pension support.” How thoughtful.

As for cheaper, more realistic ways to cut down on carbon, Sanders wants none of it: His plan bans new nuclear-power plants in pursuit of 100 percent “sustainable” energy.

No “false solutions, like nuclear, geoengineering, carbon capture and sequestration, or trash incinerators” for him, he says.

It’s classic Bernie: Propose something so radical it makes you look bold and serious — even if it’s so out-of-touch that no one can actually take it seriously.

His timing’s good, too: The plan comes just as Democratic voters may be looking for a new climate-change champ, now that Washington state Gov. Jay Inslee has quit the race.

And remember: Climate change isn’t the only area where Sanders vows to spend other people’s money by the planet-load. His Medicare-for-All plan, for example, would run, by some estimates, as much as $40 trillion. That’s 10 times the US budget.

No doubt, Sanders will lock up the Spend-Till-You-Drop vote. Democrats looking for someone more serious, on the other hand, might want to look elsewhere.