If you were asked what fuels are used to generate electricity, natural gas, coal and renewables would probably come to mind first. But oil is still a factor—albeit one that's showing a huge decline.

In 2001, oil represented 3.1 percent of America's total power generation, according to the Energy Information Administration. But by 2017 it was down to just 0.3 percent, a drop of 89 percent.

"The 2001 to 2017 decline in the oil-powered electricity generation continues the decline that began following the oil price shocks of the mid-1970s, which raised the price of oil-powered generation, and the emergence of nuclear power generation in the late 1970s and early 1980s," EIA said in its Electricity Monthly Update released May 24.

"The recent decrease of oil-powered generation resulted from a variety of factors including strong growth in natural gas generation, as well as growth in both wind and solar generation," the report added.

But that's hardly the end for black gold. EIA noted that there's still strong regional demand, including in Hawaii, where oil is the leading source of generation, accounting for two-thirds of the state's electricity. And Alaska depends on oil for nearly 15 percent of its total generation.

Oil also plays a strong seasonal role. EIA pointed to this past January, when parts of the eastern seaboard were gripped by extreme cold. That led to oil accounting for more than 10 percent of January's total electricity generation in Delaware (23.1 percent), Maine (14.2 percent), Massachusetts (13.3 percent), and New York (10.7 percent).