Cantero said the law provides enough guidance according to precedents set by prior Supreme Court rulings. Both maintained that their clients have confirmed their intent to go forward with the nuclear projects as long as they remain feasible. Davis challenged those, claims saying the commission relied on "squishy kinds of activities" to determine the utilities' intent.
Justice Charles Canady said the law is a response to very complex and dynamic circumstances.
"Things change, and the recognition that some circumstances may occur, which would cause the plans to change is just a recognition of reality," Canady said as he questioned Davis.
Justice Barbara Pariente, though, said the nuclear cost recovery law seemed like a "win-win situation" for the utilities because if plants aren't built they don't lose anything while customers do.
Grimes acknowledged that utilities stopped building nuclear plants decades ago for one reason or another.
"Maybe Three Mile Island?" Pariente asked.
The partial meltdown of a Three Mile Island reactor in 1979 is considered the worst commercial nuclear power plant accident in U.S. history.
The commission approved the full $196 million sought by FPL, but cut Progress Energy's $141 million request to about $55 million.
Cantero said the nuclear projects are costly but eventually will save consumers billions by reducing fuel costs.
"The statute was enacted because the utilities don't have the money and can't borrow billions of dollars, so they needed incentives," Cantero said. "That incentive is working."