Such was outcome of a study, conducted by the National RenewableEnergy Laboratory (NREL) between Avgust 2015 and December 2016 on the buses of californian public transport operator Foothill Transit.
Test concluded twelve Proterra electric buses, used by Foothill Transport, which operates lines in San Gabriel and Pomona valleys in Southern California and also connects them with Pasadena and southern suburbs of Los Angeles. NREL conducted the test on the line 291, which employs two overhead fast charging stations.
The use of twelve electric buses was then compared with the use of eight CNG buses with similar dimensions and brought out some interesting findings. The most striking one was, that electric buses can, in some cases, be even up to eight times more efficient than buses, which use compressed natural gas. Average operating costs of electric buses were 0,37 dollars per mile (0,41 dollar with included 10 % losses fro charging) and the costs of operating CNG buses reached 0,50 dollars per mile.
Electric buses consumed 2,17 kWh of eletricity per mille, which equates to 17.35 miles per diesel galon equivalent, and CNG buses had an average fuel economy of 4,34 miles per diesel galon equivalent. Researchers also considered the fact, that buses did not drive on the same line, and finaly came to conclusion, that, if used on the same line, the difference in buses economy could ammount up to eight times.