After years of refusing to acknowledge it, Arizona's biggest electric company on Friday affirmed that it donated millions to dark-money political groups in 2014 that helped elect two candidates who would set prices APS charges customers.

Arizona Public Service and its parent company, Pinnacle West Capital Corp., made the disclosure in a response to requests from regulators, including a subpoena from one elected to replace a commissioner APS helped into office.

The disclosure showed that in 2014, Pinnacle West gave $12.9 million to 16 different political groups. The company said in its letter to the commission that $10.7 million went to groups that contributed to the Corporation Commission elections that year.

The five Corporation Commissioners set rates and policies for APS and other regulated utilities.

"APS is providing this information today voluntarily in the spirit of putting behind us any further debate regarding political spending, and with the hope that we can focus on the future to further the energy and economic goals of the state," Vice President of Regulation Barbara Lockwood wrote in a letter accompanying the documents.

The letter and 453 pages of documents were a response to a subpoena from Sandra Kennedy, a Democrat elected to the commission in November. Two other commissioners, Boyd Dunn and Robert Burns, also had requested the information.

Burns fought unsuccessfully for years to get APS and Pinnacle West to turn over the information, but previously didn't have the support of other commissioners.

Kennedy was sworn in Jan. 7, and in a week, opened an investigation into the political spending of APS and Pinnacle West.

She said she received three boxes of documents at 4:15 p.m. She said she is hopeful the disclosure marks a turning point for the utility because it is unsavory for a regulated utility to help elect its regulators.

"I'm hoping under their new leadership, there will be a new direction," Kennedy said.

Jeff Guldner was named president of the utility in December. He previously was a vice president of policy.

"I'm going to put a lot of faith and a lot of hope that with Jeff Guldner and his team that we will not see any more expenditures when it comes to electing the very individuals that regulate them," she said.

It all started with a debate on solar

APS's turn into dark-money started with a debate over rooftop solar policies in 2013. That's when a group called TUSK, or Tell Utilities Solar won't be Killed, was launched by public relations person Jason Rose.

TUSK pushed to preserve net metering, a system where utilities give customers with solar on their roofs a one-to-one retail credit for each unit of energy that their panels send to the power grid when the energy isn't being used in the home.

APS was seeking changes to net metering that would have reduced the savings solar customers get by installing panels.

In 2014, Republican candidates for the Corporation Commission — Vernon Parker and Lucy Mason — were supported by TUSK, though they said they didn't ask for the support. They did, however, attend a solar rally organized by the group.

APS previously had declined to get involved with races for the commission. But then, a group calling itself "Save Our Future Now" mailed voters fliers that criticized Parker for previous troubles with the Small Business Administration and a failed congressional campaign.

Parker and Mason accused APS of funding the group.

APS would not acknowledge doing so, but said in a letter penned by Executive Vice President Mark Schiavoni that APS could no longer promise its money was not involved in the campaigns.

The race was contentious. A solar-leasing organization ran TV ads that portrayed Little as a Pomeranian "lap dog" to APS.

But the other two Republican candidates, Forese and Little, defeated Mason and Parker, and went on to defeat Democrats Sandra Kennedy and Jim Holway in the general election.

Forese and Little got $3.2 million in dark-money help along the way from Save Our Future Now and the Arizona Free Enterprise Club. It was not immediately clear where the other $7.5 million was spent.

While APS was widely suspected of contributing the money, it was not confirmed until Friday's response to the commissioners.

But many people tried over the years to expose APS as the source of the dark money.

The following year, a public records request from a clean-energy group revealed that Republican commissioner Bob Stump had texted extensively with an executive at APS, Forese, Little, and the president of the Free Enterprise Club.

It would violate election rules if Forese and Little coordinated with the nonprofit over the money it was spending to help get them elected, and all of the participants denied there was coordination.

The content of those texts had been deleted. A judge who reviewed what was recovered during a protracted court battle determined the contents were not public records and they were never publicly disclosed.

Watchdog reacts

The San Francisco-based Energy and Policy Institute, which advocates for renewable energy and also can be considered a dark-money group because it doesn't disclose its donors, has frequently criticized the Corporation Commission for being too close to APS.

"I can't say I'm shocked because this is what everyone suspected all along," said EPI's Executive Director David Pomeranz of Friday's disclosure.

"Just because I'm not surprised doesn't mean we shouldn't be outraged by it. It is such a basic perversion of government, and unfortunately, they got away with it. It's not even a euphemism. They were trying to buy their regulators."

APS faces backlash

The foray into dark-money politics has come back to haunt APS.

Forese, who was unable to escape the cloud cast by the dark money spent to help him, lost in the Republican primary last year. Little took a job in Washington, D.C., before the end of his term.

Not only did Kennedy return after her 2014 defeat to win the most votes in last year's election, but all the 2018 candidates from both sides of the aisle discussed the need to crack down on the utility and it's rates.

The commissioners launched the investigation into APS political spending, along with a separate investigation into the companies' earnings. And a customer complaint over the fairness of APS rates is scheduled to be considered this year.

Kennedy and Pomeranz both said they are eager to dig through the hundreds of pages of documents from APS to see what else they might reveal.

"I'm glad that they did respond and am just looking forward to diving into it," Kennedy said.

Reach reporter Ryan Randazzo at ryan.randazzo@arizonarepublic.com or 602-444-4331. Follow him on Twitter @UtilityReporter.

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