The terms of the investment in Astrum Solar, announced Monday, were not disclosed.
In regulatory documents filed in early June, Astrum Solar said it had raised $3 million in an equity offering. Investors were not named.
Astrum Solar said Constellation's investment would help the 125-employee company expand its business to residential customers across the country. Astrum Solar serves homeowners and some small businesses in 10 states, including Maryland, as well as in Washington, D.C.
The investment complements Constellation's commercial and industrial solar business, which has 95 megawatts of power generation, executives said.
Constellation's BGE Home, an unregulated company that provides electricity and other energy services, has an existing partnership with Astrum Solar.
The Baltimore company also has been aggressively expanding its residential power business, offering electricity to households in Maryland, New Jersey, Pennsylvania and Illinois. In addition, Constellation recently acquired two residential power suppliers, expanding its coverage to other states, including Texas.