Maryland's utility regulator has given Chicago-based utility company Exelon Corp. approval to purchase Baltimore-based Constellation Energy Group Inc., according to Bloomberg.

The deal has been under review by the Maryland Public Service Commission for the past nine months, after residents raised a series of concerns about the potential impact on electricity rates.

Maryland has a particularly strict set of guidelines for the purchase of public utility companies, requiring that any deal must bring customers substantive benefits, rather than just requiring that they must not harm customers as in most states.

But the deal was able to meet even these stringent standards, with Exelon agreeing to an array of 40 different conditions to help provide benefits to the residents and businesses of Maryland. These conditions ranged from required investments in renewable electricity to a $100 rebate on electricity bills for every customer in subsidiary Baltimore Gas and Electric's service area.

The Baltimore Sun notes that Constellation is the last locally-owned Fortune 500 company in the Baltimore area, making the proposal a particularly sensitive issue, but agreements have now been struck not only with the PSC but with the state's governor before that.