The Arizona Corporation Commission is reducing incentives provided by Tucson Electric Power Cop. for residential rooftop solar installations to generate electricity or heat water.

The commission also is eliminating Tucson Electric’s incentives for commercial customers’ renewable energy generation, according to the Arizona Daily Star.

Commissioner Gary Pierce says the cuts approved Wednesday are justified because the costs of systems are dropping and because ratepayers need to be protected from rising costs of the state’s renewable energy program.

The commission increased by $5 million Tucson Electric’s spending for renewable energy under a state mandate for utilities to gradually increase their use of solar and other renewable sources.