Sixty percent of the power Pepco sold its customers in 2013 was generated from fossil fuels. (Pepco)

Updated 4:20 with Pepco statement

Inside your Pepco bill this month you will likely find a slip of paper showing where your power came from in 2013.

What it shows may surprise you: For most D.C. residents — the 86 percent of households who buy their electricity from Pepco rather than from another supplier — roughly 60 percent of their power is generated from fossil fuels, with another third from nuclear generators.

Only 5.2 percent of Pepco’s standard power mix is from renewable sources — mainly wind, hydroelectric and solid-waste byproducts — which is under the 9 percent renewable target in D.C. law. (Suppliers can comply with the law by purchasing credits from other suppliers.)

Pepco says it follows the many laws and regulations it’s subject to and notes in a statement that its fuel mix is governed by the regional market it is part of and is closely monitored by regulators. But 2012 data posted on Pepco’s web site shows that its renewable delivery percentage lags in D.C. versus the other jurisdictions where it operates: 4.4 percent in D.C. versus 5.9 percent in Delaware and 9.1 percent in New Jersey.

So here’s a reminder of how buying electricity works these days. If 5 percent seems low to you, you have choices beyond Pepco’s “standard offer service.” You can buy your power from more than a dozen other companies, many of which offer greener options. The power is still distributed through Pepco’s lines, and a portion of your power bill pays Pepco for that distribution regardless, but who you pay for the generation and transmission portions are up to you.

The D.C. Public Service Commission publishes a monthly schedule of third-party suppliers’ rates. For instance, this month, a household using a moderate level of 700 kilowatt-hours a month can expect to pay about $88 for Pepco’s standard power offerings. But if that household wanted to buy 100 percent wind power, plans are available from Washington Gas Energy Services ($113), Viridian Energy ($121), Ethical Electric ($113). Those rates are for a one-year contract. (Pepco’s generation and transmission rates are set once a year, effective June 1, and are slightly higher in summer months than winter months.)

If the ultimate cost of your power is what matters most to you, Pepco may be your best bet for now. While a couple of third-party D.C. suppliers are currently underselling Pepco for short-term, month-to-month contracts, those rates are more volatile than Pepco’s rates, set once a year, or those offered under longer-term contracts.

In any case, it’s your right to shop around.