As the lame ducks in the City Council prepare to exit, they’re making certain that the door hits New Yorkers as they make their way out.

Speaker Corey Johnson & Co. are expected to pass legislation banning new natural-gas hookups this week, and Mayor Bill de Blasio (another lame duck who won’t be around for the consequences) is expected to sign it: It would require all new buildings under seven stories to be all-electric by 2024 and ones over seven stories by 2027.

This fit of green posturing is a big hit to developers, landlords and tenants. All-electric buildings are more expensive to build and maintain. The added electric demand will also spike the city’s electricity rates — already 50 percent above the national average — a particular bane to lower-income residents.

And it’s not all that green, since most electricity is generated from fossil fuels. (The state’s lofty goals to change that are another expensive nightmare.)

It’s another ticking time bomb that will explode on Mayor-elect Eric Adams’ watch, after the pols that passed it are long out of office.