Democrats also noted Republicans have supported the projects now being scrutinized.
Jeffrey Solsby, a Republican spokesman for the committee, said in a statement that Cummings mischaracterized the committee's work.
Sending "this freakish missive on energy loans speaks volumes about his own deficiencies as a congressional investigator," Solsby said.
Michael McKenna, an oil-industry lobbyist, said he anticipates more such exchanges as investigations into the loan program move forward. Congressional investigations may help Republicans say Obama hasn't lived up to his 2008 campaign pledge to change the culture of Washington, McKenna said.
"We're going to spend more time on it for sure, because there is more out there," McKenna, president of MWR Strategies Inc. in Washington, said in an interview.