We already know that 84% of new buses will be electric by 2030, which should bode well for inner city air quality. But—just like electric cars—the emissions produced in the generation of electricity need to be taken into account too.
Of course, anyone who has followed the Union of Concerned Scientists (UCS) work on quantifying the benefits of electric cars will likely know that the "long tailpipe" argument only goes so far. Electric cars are greener than gas, literally everywhere.
Now the UCS has done similar work for buses. And, once again, electric buses come out firmly on top.
There are, however, pretty big differences in terms of quite how much of a benefit they offer.
In California, where renewables are surging (and where LA is aiming for an all electric bus fleet, and utilities are pushing hard too!), they get the equivalent of 21.2mpg! That, of course, is not a particularly impressive number compared to your average family car, but it's important to understand—as UCS scientist Jimmy O'Dea points out—that a comparable diesel bus gets only 4.8mpg. Even in coolest of coal country, the advantages are significant, with the lowest mpg equivalent being 7.4mpg. That means that going electric is between 1.4 to 7.7 times better in terms of greenhouse gas emissions than your average diesel bus in America.
Natural gas is marginally cleaner than diesel, as are diesel hybrid buses. But UCS says we're only talking about improvements of around 12% in terms of emissions for either technology. And it's important to remember, of course, that unlike fossil fuel supplies, the grid just keeps on getting greener. So we can expect to see this gap continue to grow: