Roughly, to be safe, assume an extra 1.5kWh per thousand feet in addition to the normal usage for the miles covered. I think that's more useful than what mogur suggests, because it is independent of steepness.
Great, so assuming 24kWh/100 miles, this is 5.4 miles for 1000 feet of climbing, +2 miles of normal distance, which would be roughly 7.4 miles total energy consumption.
--Now what is the regeneration efficiency? If I assume 5.4 miles of potential energy, then 5.4% of 100 miles total distance could potentially be recovered. Should I assume 50% regeneration recovery or maybe less? It will be fun to test out. We could start with a 98% charge (if you can tune the charging to that level) and see if we can get to 100% near the bottom of our hill...