Man, that sounds like a huge win and not weird at all, more cities need to get on that train. We had something close here in Tucson last August when it hit 110 for like a week straight, and the co-op asked people with batteries to hold off charging until after 6pm, and it actually dropped the peak load enough that they didn't have to fire up an old gas plant. My neighbor has a Powerwall and he was glued to the app watching it dump power back to the grid, said he made like 30 bucks that week just from that. The whole thing only works when enough people join in though, that part you nailed, one house alone does nothing but a thousand houses together is basically a power plant.

What was your chip load before and after? Going from 3000 to 6000 is a big jump and if you were running too light a chip load at the lower speed, that's what was killing your inserts, not the rpm itself. Rubbing instead of cutting builds heat fast. Curious if you kept the same feed per tooth when you made that change or if you actually dialed it in.