In six short months, a new dark age will begin to descend on America. Starting on Jan. 1, 2012, federal law begins a phased ban on Edison’s gift to mankind: the long-lived and long-loved incandescent light bulb.

The feds demand that they be replaced with Compact Fluorescent Lamps — squiggly bulbs full of mercury and other mysterious stuff that are supposed to save cash and energy.

But at what cost?

Congress appears not to have pressed the issue before banning the old bulb. So let’s take a long look at the dubious efficacy of the new one.

The 100-watt-equivalent CFLs run about $4 a pop — five times the price of incandescents — and that cost doubles for special bulbs that work with dimmers and three-way lamps.

The federal Department of Energy claims a houseful could save the average consumer $50 a year. This almost offsets the $60 you’ll spend equipping an average house with CFLs that first year.

The feds say that CFLs last for 10,000 hours, or 4.5 years, in controlled circumstances, or 10 times longer than incandescents.

But consumers live in the real world, where cold air, humidity, and just flipping the light-switch all take a toll — so no one really knows how long they’ll last in less-than-laboratory conditions.

But once the bulbs die (prematurely or otherwise), you mustn’t just throw them in the garbage.

That’s because CFLs contain mercury, a toxic pollutant. And that’s why the city Department of Sanitation wants consumers to deposit dead bulbs in one of five “Special Waste” dropoff sites located around the city.

But they are only open four days a month — so New Yorkers should plan ahead.

And they should bring their driver’s licenses to the dropoff — where Sanitation Department employees record their name, address and vehicle-registration numbers while taking careful note of the type of trash being tossed.

That seems like a real hassle, but maybe it’s not as big a deal as breaking a CFL at home stands to be.

When that happens — as it invariably will — the federal EPA recommends:

* The immediate evacuation of all people and pets from the affected room, which then should be aired out for at least 10 minutes.

* The shutdown of all air conditioners for several hours — to avoid spreading mercury vapor.

* The use of tape and damp rags to pick up broken glass — but not the use of a vacuum, because that would spread mercury, too.

So, what does America get in return for all this unnecessary expense and hassle?

Less light than its used to, and pallid light at that: Incandescents score a perfect 100 on the Color Rendering Index — a measure of how natural the light a given bulb produces — while most CFL bulbs rate well below an 80 on that scale.

Incandescent bulbs are not efficient — they create as much heat as light — but they get the job done.

CFLs are like the aspartame of lights — similar taste, but less flavorful.

Forcing them on consumers is like banning sugar in favor of Sweet’N Low; Americans might lose weight . . . but for sure they’ll be miserable in the process.

Thankfully, House and Senate Republicans have drafted bills to repeal the ban before it goes into effect, undoing part of a 2007 energy law.

House Energy Committe Chairman Fred Upton (R-Mich.), one of the architects of the original CFL legislation, has pledged to hold hearings on legislation meant to repeal the incandescent ban.

A timely call to his Washington office — (202) 225-3761 — couldn’t help but to get the ball rolling.

— The Editors