The nation's capital gets most of renewable energy from states as far flung as Indiana because it can't produce much on its own, according to the Energy Department.

About half of the power plants that can meet the District of Columbia's renewable energy mandate are in Illinois, Indiana and Pennsylvania, the Energy Information Administration, the Energy Department's analysis arm, said Monday.

The agency said D.C. is meeting its overall renewable energy mandate, which requires utilities to provide a certain percentage of electricity from renewable energy, by buying credits and paying millions of dollars in what are essentially fines for not having enough renewables on hand to generate electricity with, according the EIA analysis.

Last year, electricity sales totaled 11.3 billion kilowatt hours, with the mandate of 12 percent of that coming from renewable energy, the agency said. "Because D.C. has limited renewable capacity, almost all of the ... compliance targets were met by generation outside of the District through the purchase of renewable energy credits."

Utilities bought almost 1.4 million credits, representing one megawatt hour of electricity each. On top of that, utilities have to pay a fee for submitting the credits as a means of compliance. To meet just the solar segment of D.C.'s mandate, it cost utilities $20 million in compliance payments. Utilities had to pay $500 per credit to comply with the program, although the fee is set to decline after 2023.

Most of the District's renewable energy target isn't being met by solar or wind. It's coming from wood-burning power plants and those fueled by "black liquor," which is the oily waste that comes from paper mills. That's not what one might expect to meet a clean energy mandate, but both wood and black liquor are considered renewable because they are derived from plant material.

When it comes to meeting electricity demand on a 24-hour cycle, these power plants are more reliable than a wind turbine that only provides intermittent electricity.

In 2015, the renewable requirement for D.C. was 12 percent, all of which was met through the purchase of credits from out-of-state power plants.

Of the credits submitted, wind and solar generation represented 20 percent and 3 percent of the overall requirement, respectively. The bulk of the District's renewable requirement was met with credits purchased from biomass and black liquor power plants, representing 30 percent and 27 percent of the overall requirement, respectively.

The District even falls short when it comes to the only renewable energy source it can produce electricity from, rooftop solar.

As of last month, it can generate 22 megawatts of electricity from solar, which represents only 0.3 percent of total eligible electricity under its renewable energy mandate. On top of that, the District just approved doubling its mandate from 20 to 50 percent renewable energy by 2032.

Although D.C. has been able to meet its overall renewable energy target since 2009, with the help of credits, "it has often fallen short of the solar-specific target," according to the analysis. The D.C. Public Service Commission expects it will need at least 70 megawatts of solar to meet its target in 2016, but had only about 43 megawatts available to it as of last month, said the administration.