Tucson Electric Power Co. plans to install rooftop solar panels at customers’ homes in exchange for a fixed electric rate for 25 years.

TEP’s Residential Solar Program was approved Thursday by the Arizona Corporation Commission as part of the utility’s 2015 renewable-energy plan, will be available next spring to a total of 500 to 600 customers.

The program will let customers go solar with no installation or maintenance costs, though an upfront $250 administrative fee will apply.

Participants will have their electric service for a set monthly fee that would remain fixed for up to 25 years. The fixed monthly electric rate will roughly match customers’ current average bills, generating savings if TEP’s rates or energy costs increase in the future, the company said.

The program is part of a larger renewable energy plan budgeted at about $40 million, or about the same as this year. All incentives for new customer-owned solar installations — including hot-water systems — have been phased out.

The TEP-owned rooftop solar program was favored by regulators and consumer and environmental advocates, but solar-leasing companies had opposed it as an unfair intrusion on the private-sector solar market.

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