For all of President Obama’s talk Tuesday night of boosting US energy production, he has a huge problem: The American left — a vital part of his political base — seems determined to force us down the opposite path. Indeed, the “Big Green Extreme” fights energy even when it means harming the environment.

Take Obama’s decision last week to halt the Keystone XL pipeline. It defied common sense. Letting the oil flow from Canada to refineries in Texas would have generated thousands of high-paying US jobs (hence the unions’ anger with the president), given our nation’s flagging economy a big boost and reduced our energy dependence on less-friendly and less-reliable suppliers.

Plus, killing the pipeline is a clear loser for the environment. The oil from Canadian tar sands isn’t staying in the ground. It’s heading overseas via tanker to China, where it will be refined under regulations far looser than ours. Every step of the way, the process is less “green” than the Keystone route.

Oh, and we’ll have to import more oil via tankers from overseas, or carry crude oil from Canada in trucks or on rails.

The assault on energy is relentless. Last year, the US Chamber of Commerce identified 351 energy projects stalled by “not in my backyard” suits, regulatory red tape and, of course, endless challenges from greens. Almost half these projects (140) are renewable-energy ones.

In Alaska and Idaho, for instance, environmental groups are challenging hydroelectric projects, claiming they could threaten fish habitats, water quality or tourism. Wind and solar projects, meanwhile, face opposition because they might threaten desert tortoises or migratory birds.

There’s also the transmission issue. Wind and solar plants are built in remote locations; the lines to take the power to consumers may cross wildlife refuges, protected grasslands or bodies of water — all of which are targets for more environmental objections.

The $800 million Green Path North transmission-line project would’ve helped California meet its goal of producing 33 percent of its electricity from renewable sources by 2020, but the Los Angeles Department of Water and Power canceled it after opposition from environmental activists.

In New York alone, the Chamber identified 19 energy projects, 11 of them wind, held up for one reason or another. And that doesn’t include the state’s green-driven ban on fracking to extract natural gas from shale.

As the president alluded to on Tuesday, fracking has produced a natural-gas boom in much of the country — without environmental harm. And natural gas is cleaner than the oil or coal it typically replaces. Yet environmentalists nationwide still crusade hysterically against it, if with less success than in New York.

The green hostility to “carbon” fuels is well-established; it’s the big reason why oil and gas production on federal lands is down more than 40 percent in a decade. And it’s why the drop is accelerating under this administration — even as the Obama team’s refusal to grant new offshore-drilling permits is slowing that production. Of course, the Obama Environmental Protection Agency’s “war on coal” is forcing coal plants to shut down across the nation.

But environmental activism has gone to a radically new level — one that aims to block all energy projects, using any excuse in the book, while destroying jobs and raising the cost of energy in the process.

Because energy goes to produce just about everything, Americans aren’t just hit at the pump and on their electric bill. Higher energy prices ripple through the economy, punishing us all again and again.

We can effectively manage and reduce risk so the economic benefits are great and environmental risks are minimal. But we can’t eliminate risk unless we simply don’t build the projects — which is exactly what many green groups now seek.

Energy is our economy’s lifeblood, and the environmental zealots want to stop that flow.

Nicolas Loris is an energy- and environmental-policy analyst at The Heritage Foundation.