WASHINGTON — A unanimous Supreme Court ruled Tuesday that Maryland officials overstepped their authority when they offered financial subsidies to encourage construction of a new power plant in the state.
The justices said the Maryland plan interferes with federal law governing wholesale electricity rates.
The ruling is a setback for Maryland and other states that want to ensure a reliable supply of electricity for customers at reasonable rates.
The case involves a 2012 decision by state regulators to order construction of a $775 million natural gas power plant in Charles County. Officials offered the winning bidder — Silver Spring-based Competitive Power Ventures — a financial incentive by requiring utilities to buy electricity from the plant for 20 years at a fixed price.
Lower courts sided with rival power suppliers who said the incentive interfered with pricing in wholesale markets, which are subject to federal regulation.
Writing for the high court, Justice Ruth Bader Ginsburg acknowledged that states have authority to encourage development of in-state power plants. But she said Maryland's program "impermissibly intruded on the wholesale electricity market."
She said the power to set wholesale electricity prices lies exclusively with the Federal Energy Regulatory Commission.
Ginsburg noted that the court was not preventing states from taking other measures to encourage development of new or more environmentally friendly power plants. That could include tax incentives, land grants, direct subsidies or other actions that don't intrude on federal authority, she said.
"Nothing in this opinion should be read to foreclose Maryland and other states from encouraging production of new or clean generation through measures untethered to a generator's wholesale market participation," she said.