Clearway Energy Group, one of the U.S.’s largest clean power developers, is launching a pilot electronic marketplace for renewable energy credits as more states push for solar and wind projects. The company has partnered with Power Ledger, which develops blockchain-enabled energy trading software, to build a system to both track and trade so-called RECs, according to an emailed statement. The initial test phase will include a Massachusetts project with 1 to 5 megawatts of generation and a second Midwest project for at least 20 megawatt, according to Power Ledger. The U.S. RECs market is valued at more than $3 billion, and transaction costs can tack on another 3% to 10%. While there are effective digital options to trace RECs from when they are generated to when they are retired, costs add up when seeking to aggregate and trade them through brokers or bilateral contracts across state lines, Power Ledger Executive Chairman Jemma Green said in a telephone interview.