COMMUNITIES across the United States are looking to replace their dirty diesel buses, ushering in what some analysts predict will be a boom in electric fleets. But transit agencies doing the buying are moving cautiously, an analysis shows.

Out of more than 65,000 public buses plying U.S. roads today, just 300 are electric. Among the challenges: electric buses are expensive, have limited range and are unproven on a mass scale.

A typical 40-foot electric bus costs around US$750,000, compared with about US$435,000 for a diesel bus. Cheaper fuel and maintenance expenses can lower the overall costs over the 12-year life of the vehicles. But those costs can vary widely depending on utility rates, terrain and weather.

The technology is still a gamble for many cities at a time when bus ridership is falling nationwide and officials are trying to keep a lid on fares, said Chris Stoddart, an executive at Canadian bus maker New Flyer Industries Inc. A top supplier of conventional buses to the U.S. market, the company has just put a handful of pure battery electrics into service.

“People worry about being an early adopter. Remember 20 years ago, someone paid US$20,000 for a plasma TV and then 10 years later it was US$900 at Best Buy,” said Stoddart, senior vice president of engineering and customer service for New Flyer. “People just don’t want a science project.”

Rival electric bus manufacturers expect dramatic growth: the most ambitious forecasts call for all bus purchases to be electric by 2030.

But even green-energy advocates are skeptical of such rosy predictions. CALSTART, a California-based nonprofit that promotes clean transportation, figures 50 percent to 60 percent of new buses will be zero emissions by 2030. Market research firm Navigant Research expects electric buses to make up 27 percent of new U.S. bus sales by 2027.

Transit agencies have found electric vehicle performance lags in extreme conditions. In environmentally friendly San Francisco, officials have resisted electrics over concerns about the city’s famously steep hills.

“The technology isn’t quite there yet,” Erica Kato, a spokeswoman for the San Francisco Municipal Transportation Agency, said in a statement.

Weather is also a major challenge.

An electric bus tested last year near Phoenix wilted in the summer heat due to the strains of running the air conditioning. The vehicle never achieved more than 89.9 miles on a charge, less than two-thirds of its advertised range, according to the Valley Metro Regional Public Transportation Authority. (SD-Agencies)