The two Republicans vying for a two-year term on the Arizona Corporation Commission (search) differed Tuesday on whether the state should require electricity providers to provide set amounts of energy from renewable sources.

Appointed incumbent Kris Mayes (search) and challenger Carl Seel (search) also used a debate to spar over their experience and qualifications to serve on the commission, a five-member elected panel that regulates utilities, securities dealers and pipeline and railroad safety.

Power companies regulated by the commission now must produce nearly 1 percent of their electricity from renewable sources, with 60 percent of that amount coming from solar.

Mayes said she would favor hiking the "environmental portfolio" standard to 10 or 15 percent to diversify the sources of supply.

"Clearly we need to only expand in this area," she said.

Seel said he was reluctant to impose a mandate and instead would like to encourage providers to invest in technological improvements that would eventually drive down the cost of renewable energy and make it more competitive with power from nonrenewable sources.

"I'm not excited to regulate and say you the consumer have to pay more," he said.

Mayes defended the mandate, saying it is what is pushing utilities to go beyond traditional sources of power.

"There are a lot of renewable sources that are totally, completely competitive. Solar is not quite there," she said.

Seel in his opening statement made a veiled reference to Mayes' ties to Democratic Gov. Janet Napolitano and then in his closing statement explicitly cited those links.

"This is a Republican primary," Seel said. "My opponent forgot to mention that she was appointed by Napolitano."

Mayes, a former press secretary to Napolitano, had given her closing statement first and did not respond to Seel's jab.

During earlier responses to questions posed by the moderator, Mayes she cited her 10 months of experience on the commission and corrected Seel on several points he made about the commission's functions.

"Kinder Morgan did pay for that test," Mayes said after Seel said the Houston-based pipeline company should pick up the tab for a safety check on a gasoline pipeline.

Napolitano appointed Mayes to fill a commission vacancy created by Jim Irvin's resignation to avoid impeachment proceedings. State law required the governor to pick a replacement from the same party as Irvin, a Republican.

Three other incumbent Republicans are being challenged by three Democrats for full four-year terms on the commission. None face primary challenges.

The debate was held at the University of Advanced Technology and sponsored by the Citizens Clean Elections Commission and the Arizona Telecommunications and Information Council.