The California Public Utilities Commission has approved an ambitious program that will see San Diego Gas & Electric build 3,000 electric vehicle charging stations for medium and heavy-duty vehicles including school buses, delivery trucks and forklifts — and SDG&E customers will pay more each month to fund it.

The still-unnamed program will build the charging stations in about 300 locations in the San Diego region over the next five years in an effort to meet a legislative mandate to reduce greenhouse gas emissions in California. It will cost $107.4 million, which will be paid by ratepayers.

SDG&E officials estimate the program will add $4.57 per year on the bills of average residential customers who use 500 kilowatt-hours per month, starting in 2022. That works out to about 38 cents more per month.

"When you look up at the sunny San Diego sky, you may not realize our air quality was recently rated poorly due to ozone pollution" by the American Lung Association, said SDG&E communications manager Jessica Packard in an email. "We are taking a major first step in helping to reduce these emissions by electrifying some of the largest contributors to our air pollution, large vehicles and equipment."

Under Senate Bill 350 passed in 2015, the public utilities commission has directed the state's investor-owned power companies to come up with clean transportation initiatives to promote the transition to electric vehicles.

The program, approved Thursday, is the first large-scale initiative of its kind in the region that focuses on medium-duty and heavy-duty, or MD/HD, vehicles. SDG&E will now look at potential sites among local businesses and public agencies to build the charging stations.

Transportation accounts for about 40 percent of greenhouse gas emissions in the state and almost 50 percent in SDG&E's service territory. More than 100,000 commercial vehicles weighing from 6,000 pounds to more than 33,000 pounds drive along the roads in the San Diego region.

Heavy-duty vehicles produce more particulate matter than all of California's power plants combined and can cause or worsen asthma and other health problems.

"SDG&E's MD/HD initiative would provide EV charging stations to support large equipment and vehicles that pollute our air, therefore reducing harmful emissions," said a statement from Robert Kard, air pollution control officer at the County of San Diego Air Pollution Control District.

The program also supports electrification of refrigerated semi-truck trailers that transport perishable goods. At least 10 percent of the program's budget must serve transit buses and school buses.

All told, as many as 6,000 vehicles can be supported by the MD/HD initiative.

The MD/HD initiative also includes money for a pilot program that uses a technology in which electric school buses can provide energy back to the power grid. Called V2G, the pilot would see the big batteries in the buses charged when renewable energy is abundant — during the day, for example, when solar production surges — and then send the energy back to the grid when demand peaks.

That can lower the costs of managing California's power grid and potentially deliver a source of revenue to fleet managers and school districts.

"SDG&E's program will fill a critical gap in the San Diego region, expanding access to cleaner air and cleaner transportation, while supporting a cleaner electrical grid," said Max Baumhefner, senior attorney for the Natural Resources Defense Council, one of the groups involved in the CPUC proceeding.

California has set a goal to deploy 250,000 charging stations in the next six years. There are slightly more than 21,000 charging plug stations in the state now.

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