Hybrid Muni Buses

The last few days I’ve seen new Muni buses that have “Hybrid Bus” signage on them. I’ve seen them mostly at the Caltrain station, which makes sense as they’re running on the 10-Townsend line currently. At half a million a pop, I wonder how much they save in terms of gas. They also skirt very close to the ground, which is pretty cool since it seems they’d be easy to enter versus the standard Muni buses (which let out the typical hiss as they lower at stops).