Minneapolis mayoral candidate Mark Andrew proposed dramatically expanding the city's investment in renewable energy Thursday by installing solar panels on up to 150 city-owned buildings.

Andrew announced the plan at a news conference in front of City Hall, flanked by several politicians and union representatives. The city now has solar panels on six buildings.

"We are proposing today to build on the fantastic work that the city has done up until now," Andrew said. "And the first step in that process is for us to set an example … that sustainability builds green jobs, builds the economy and cleans up the environment and enhances our overall quality of life."

Andrew said that existing federal tax credits, combined with utility company incentives, would help drive down the total city cost of the project — potentially by more than 60 percent. But just what the initial cost would be was a matter of dispute.

The Andrew campaign estimated that the panels could be purchased for about $2.70 a watt, which amounts to about $16 million at 40 kilowatts per building. The campaign estimated that the annual savings from the panels in the first year would be $192,000.

John Limb, a solar panel manufacturer standing among the supporters, said a more reasonable cost per watt would be $5 to $7.50, citing a recent New York Times article about how cheaper panels have defects. That would bring the cost to $30 million to $45 million.

"The really low, low numbers we're talking about are, frankly, the really cheap Chinese stuff that's coming in from overseas," said Limb, who owns Silicon Energy in Mountain Iron, Minn.

The campaign said that the more expensive panels would also be cost-efficient since they could last 100 years — as opposed to 20 or 30 years — and provide more long-term savings. The state also recently passed an incentive that reduces the cost of buying local solar equipment.

Andrew's plan would apply to park and school buildings, in addition to general municipal structures.

"Schools from my perspective are a great place for solar panels," said Alberto Monserrate, a school board member supporting Andrew.