Zero DSR Range on Gravel Roads

I'm considering buying a Zero DSR, and one use I will have for it is riding gravel backroads. I have not found any data or anecdotes on range of these bikes at moderate speed (say 30 MPH) on gravel. Does anyone have experience with this? Wh/mile is probably the best way to compare, since battery capacities differ.

Thanks,
Kevin

Easily 140+miles at 30mph. If it's very soft terrain like sand it consumes more power than asphalt meaningfully, but firm gravel is about the same.

Thanks! On what size battery pack are you basing that estimate?

I just spoke with a friend who reports 150 miles of forest/gravel roads on a 2016 DS with 13 kWh pack.