The annual sales of hybrid vehicles intended for company fleets will rise from 300,000 last year to over 830,000 within the next six years, according to Pike Research, a market research and consulting firm that provides in-depth analysis of global clean technology markets. The market for hybrid trucks and buses is expected to grow the fastest. Their share in the total number of fleet vehicles in the United States will rise to 8 percent in five years.

"Producers have started to turn towards heavy hybrid vehicles, which offer considerable economies," predicts Clint Wheelock, managing director at Pike Research. "In North America for instance, almost 10 percent of buses sold will have hybrid propulsion in 2015."

Many countries are adopting stricter emissions regulations. The use of environment-friendly vehicles leads to lower carbon dioxide emissions and saves fuel by 10 to 40 percent.

Initially, hybrid cars will be bought by government institutions, universities and municipal companies, but private businesses will soon follow suit. American firms and institutions will buy the largest number of such hybrid vehicles, with China in second place. In 2008, hybrid vehicles sold on the American market accounted for 63 percent of such vehicle sales worldwide.