Of course all they have to do is pay interest on all reserve balances…

Fed Moves Toward New Tool for Setting Rates (WSJ) An experimental bond-trading program being run at the Federal Reserve Bank of New York could fundamentally change the way the central bank sets interest rates. Fed officials see the program as a potentially critical tool when they want to raise short-term rates in the future to fend off broader threats to the economy. Launched this year, it is still in a testing stage and isn’t expected to be fully implemented for years. The Fed would use the facility to raise short-term interest rates by borrowing in the future against its large and growing securities portfolio. When it does want to raise rates, it will use securities it accumulated through its bond-buying stimulus programs as collateral for loans from money-market mutual funds, banks, securities dealers, government-sponsored enterprises and others. The rates it sets on these loans, in theory, could become a new benchmark for global credit markets.