> The problem with buses is that utilization is very low. Most buses, most of the time, run near empty.
Huh. That doesn't resemble my experience, except for rural/small-town services, which are very much provided as a form of subsidy, not a viable business.
> But I doubt, fully electric buses make sense: as long as dispatch-able power (ie your marginal producer) is a thermal plant you get 60ish% thermal efficiency at best minus transformer and transmission losses.
That's still quite a bit better than diesel engines, where for realistic engines you're talking about 40% _in ideal conditions_, but much worse in stop-start conditions (you will do better with hybrids, granted). Gas also have considerably lower CO2 intensity per thermal watt than diesel does (your fossil fuel electricity production is probably mostly gas in most countries).
But, also, in countries with a lot of unreliable renewables, buses charging overnight can be used as a power sink. For instance, in Ireland, our wind generation can be anything from almost nothing to greater than total system demand; reasonably often, wind turbines actually have to be stopped to reduce output, especially at night. At that point, charging the bus is for practical purposes free, or may even have a modest negative cost (the network will sometimes pay for power consumption).