For almost as long as it has been a state, Alaska has been powered by the natural gas buried beneath Cook Inlet, an estuary on its southern coast.

The gas used to be so plentiful that Alaska not only used it to heat homes and make electricity, it shipped tankers of the fuel overseas.

Now, most of the drilling companies have gone, and the Cook Inlet gas is dwindling. Officials expect that, in the next several years, they may not have enough of the fuel to keep all the lights on in Anchorage, the state’s biggest city.

Any shortfall would most likely come in the dead of winter, when temperatures routinely fall below zero. First, the utilities would ask people to turn down their thermostats and put off washing clothes. Then, darkness. Temporary power shut-offs would envelop one neighborhood, then another. If that still were not enough, businesses would be forced to go without gas.

The prospect of running short on energy would be daunting anywhere, but it is a particularly bitter pill in Alaska, which has built its economy on oil and gas.

Alaska still produces a lot of gas. The problem is that most of it is being harvested some 800 miles away from Anchorage, from a remote slice of Arctic tundra called the North Slope; currently there is no pipeline to transport it to Anchorage.