The Union of Concerned Scientists have released a report that electric buses (EBs) are 1.4 to 7.7 times better than a diesel bus in terms of miles per gallon emissions-equivalency. The key finding in the report is that EBs generate fewer emissions even in states where the grid relies heavily on coal.
EBs have significantly fewer moving parts and lower maintenance than buses fueled by diesel or compressed natural gas. The environmental value of EBs will only increase as states continue to move from coal to renewable energy, such as hydropower, wind and solar.
In my opinion, large metropolitan cities should be aggressively moving from diesel and compressed natural gas buses to EBs. The purchase price of a buss with a combustion engine is less than an EB. However, EBs are more cost effective than combustion engine buses when lower operating costs and lower fuel costs for electricity are factored into the equation. Air quality alone should convince large metropolitan cities to rapidly move to EBs.