New Mexico is giving businesses a new reason to try using the sun to generate their own electricity.

A state program that offers utility customers incentives to put solar panels on their roofs now includes larger systems for businesses.

On Tuesday, a snow day for most state employees, the Public Regulation Commission unanimously voted to require the state's largest utility to pay businesses 15 cents for each solar-produced kilowatt hour they use. The commission voted to keep the residential incentive at 13 cents per kilowatt hour.

Privately owned solar power systems help Public Service Company of New Mexico comply with state requirements to draw a percentage of electrical power from alternative energy sources. PNM gets most of its power from coal-fired generating plants.

Residential systems have a capacity of up to 10 kilowatts, while commercial systems have a capacity of up to 1 megawatt.

"This is essentially the opening of the door for businesses to take advantage and start to green their businesses," said Mike Mattioli, owner of Consolidated Solar Technologies, an Albuquerque company that designs and builds medium and large photovoltaic (PV) systems.

Cynthia Bothwell, PNM's manager of integrated resource planning, had hoped the PRC would approve 13 cents for the commercial systems. But she was pleased the commission decided against requiring PNM to pay for unused energy produced by its customers — energy that returns to PNM's grid. However, customers will save money through "net metering," meaning their utility bills will have a deduction for whatever unused energy returns to the grid.

PRC Chairman Jason Marks said the excess-energy provision was included to keep customers from essentially becoming miniutilities. And while solar advocates pushed for a bump in the residential incentive, he said 13 cents has already spurred growth in the program. In 2007, 187 customers had PV systems, and it's expected to rise to 404 this year.

Solar advocates have argued for as much as 30 cents per kilowatt hour for residential systems, saying a greater incentive was needed to get serious about reducing the demand for fossil fuels.

State law requires PNM to get 6 percent of its total energy sales from renewables, such as wind and biomass, although residential PV systems now account for less than a half-percent of the utility's nearly 500,000 customers. The requirement rises to 10 percent in 2011.

Tuesday's meeting was Ben Ray Luján's last as a commissioner before he joins Congress next month, and a stream of staffers gave him Christmas gifts and handshakes. He teared up when Marks gave him a certificate engraved in Nambé Ware. His father, state House Speaker Ben Luján, D-Nambé, later stopped by to congratulate his son.

Contact Doug Mattson at 986-3087 or dmattson@sfnewmexican.com.