First Solar, Inc. (Nasdaq: FSLR) is returning to its roots with a new 250-megawatt photovoltaic manufacturing facility planned for Mesa, Ariz., near its Tempe headquarters. And it looks like Maricopa County may welcome the company back with as much as $20 million in incentives.

The new factory is part of First Solar’s efforts to remain one of—if not the—highest producing manufacturers of photovoltaics in the world.

Last week, the company announced that it broke ground on a 250-megawatt photovoltaic manufacturing plant in Vietnam. Both facilities could be further expanded, said First Solar spokesperson Alan Bernheimer. In all, the company plans to ramp production capacity to 2.9 gigawatts (2,900 megawatts) of photovoltaic modules by the end of 2012.

The county’s board of supervisors will decide March 30, whether it should approve the incentive package that the county manager worked out with First Solar.

The package would offer up to $20 million contingent on First Solar reaching certain employment and financial milestones, said Chris Bradley, Maricopa County’s director of business strategies and health care programs.

“There’s no deal until and if the board approves the contract,” Bradley said.

“The Maricopa County incentive plan is tied to job creation,” said Bernheimer. “First Solar expects to create the jobs [600 ongoing manufacturing jobs], and in return, the County expects to provide the incentives.”

Under the proposed contract, First Solar would have to bring a total of 4,800 high-paying jobs, with an average salary of $48,575, to the county over the next 10 years, Bradley said.

“The median wage is about $34,000 here,” said Bradley. “This whole thing is pursuant to the board of supervisors’ strategic goals to increase the income of Maricopa County and to increase the share of employment in exporting industries.”

The deal also is contingent on First Solar’s capital investments and that it will export—out-of-state—80 percent of the modules made at the plant, according to Bradley.

“There’s an assumption that there will be $1.6 billion in capital investment made by First Solar that would hit the property tax roles of Maricopa County,” he said.

No payment of funds will happen until they make capital investments.

“Funds will be dispersed in increments based on [meeting certain levels] up to 20, in $1 million payments,” Bradley said. For each $1 million payout, First Solar must create 240 jobs and make about $80 million in capital investments.

The county is estimating that it would recover the $20 million in new county general fund tax revenue within about nine years, according to Bradley. That’s less than the 10 years that First Solar has to reach the milestones.