Lawmakers will hear about the influence big banks can have over the U.S. power markets when they can own plants, supply fuel to those units and trade based on the electricity they generate.

Thursday’s hearing before a Senate subcommittee was tied to a report, “Wall Street Bank Involvement With Physical Commodities,” that highlights JPMorgan Chase & Co.’s entry into the power plant business in 2008 amid the worst financial crisis in the U.S. since the Great Depression.