Con Ed banned new natural gas customers in much of Westchester last Friday. Now the greens who are driving that gas shortage want to spread the trouble to the city and Long Island.

On Tuesday, 350.org — an extremist enviro group working, its website says, to thwart “new coal, oil and gas projects” — released a “study” blasting a pipeline that would bring gas from Pennsylvania to the Rockaways, via the Lower New York Bay.

The Northeast Supply Enhancement Project “would incentivize reliance on gas, which is way more carbon-intensive than renewables,” says Robert Wood of 350Brooklyn. So what? Renewables (wind, solar, etc.) can’t supply enough power — now or any time soon.

And gas is a winner for cutting CO₂ emissions. Oil-fueled power plants, for instance, give off 42 percent more carbon than gas. It’s one reason the nation has been switching to gas. The city itself requires gas over oil (Con Ed has converted 5,000 buildings).

Nationwide, the switch has helped plunge emissions 13 percent since 2005, faster than many European countries.

But the extremists want to end all fossil fuel use now. And Gov. Andrew Cuomo has worked to do their bidding, notably by nixing pipelines; Westchester’s gas shortage is a result.

Cuomo clearly knows the damage he’s causing: As Con Ed’s new customer ban went into effect, he tried to make amends by offering the county $250 million (of taxpayer and Con Ed-customer money) for “clean-energy alternatives” and to get folks to cut back on gas use. Expect many investors to shun the county nonetheless.

Now Cuomo & Co. must decide the fate of the NESE. National Grid, which would deliver the gas, says “current pipeline infrastructure” is at “capacity.” It needs the new line to “keep pace” with consumer demand in the city and Long Island and to “avoid gas-supply constraints.”

If the gov doesn’t stop giving extremists a veto over growing the region’s energy supply, New York is going to see ever-growing shortages.