Enough, already.

Congress and the president should extend the production tax credit for renewable energy. The program, slated to sunset at the end of December, provides a 2.2-cent credit per kilowatt hour for the first decade of a new solar, thermal, wind or, in some cases, bioenergy plant.

Opponents argued against the modest credit while saying nothing about billions of dollars in tax breaks and other benefits afforded to traditional energy producers.

We do not argue that all breaks to oil, gas and coal companies should be abandoned. Rather, we believe that a mix of old and new energies is necessary to wean the nation off of foreign oil and to begin to mitigate climate change.

But just as oil companies have been rewarded for the investments they’ve made in new oilfields and technologies, so, too, should the renewable sector be nurtured.

Unfortunately, the production tax credit has suffered from uncertainty.

With certainty, companies such as Vestas Wind Systems, Siemens Energy Inc. and others invested many millions of dollars in new plants to manufacture turbines, nacelles, towers and other equipment to keep up with robust demand.

With uncertainty, those same companies have slashed jobs by the thousands, including at operations in Windsor, Brighton, Pueblo, Louisville and elsewhere.

Could it be any simpler? The production tax credit helps create thousands of jobs; uncertainty over its extension helps eliminate thousands of jobs.

“The cycle begins with the industry experiencing strong growth in development around the country while the PTC is firmly in place, and in the years leading up to the PTC’s expiration,” the Union of Concerned Scientists states. “Lapses in the PTC then cause a dramatic slowdown in the implementation of planned wind projects.”

Enough.