CLEVELAND – A new study expects hybrid-electric vehicle demand to hit nearly 8 million by 2020, led largely by purchases in the United States and the cost of fuel, according to the Web site www.earthtimes.org. The Freedonia Group Inc., a Cleveland-based industry research company, said an increasing demand for energy in the world, high and erratic fuel prices, and stepped up standards for emissions, will increase the demand to 3.9 million units by 2015. According the study by World Hybrid-Electric Vehicles, that number will nearly double by 2020. Hybrids are more expensive than regular vehicles, an average of $1,000 to $3,000, but the report expects that disparity to shrink as production increases. The primary markets for HEVs will remain in the U.S., Western Europe, and Japan, although the rapidly growing Chinese market is also expected to experience relatively strong demand for these fuel efficient and environmentally friendly vehicles, according to a release by The Freedonia Group.