How much range do you get on yours? I am interested in this one because it has 30 mile range and replaceable battery. Price is pretty decent at less than 1500. Link: http://www.genze.com/e-bikes/
That bike has 1.75" tires and I've got big 3" wide tires, and I'm only running about 10-12psi, with front suspension sucking up what feels like half of my pedal power, so rolling resistance is much higher and efficiency is much lower for me.
The "efficiency" is calculated as watt-hours per mile. You'll see different numbers depending on all sorts of factors (pedaling, speed, terrain, tires), but we can just hand-wave it all away (science!) and say 20wh/mile. That gives you about 15 miles and me about 35.
I've only run the battery down once so far, and that was only from a 90% charge, with a lot of mud, snow, and general screwing around. The battery cut out at just over 25 miles.
The bike you linked has a 250w motor. Running it at 100% for an hour, if you were able to average 12.5mph for that time, that gives you 20wh/mile.
Based on the watt-hours we calculated earlier, and the manufacturer's claim of 30 miles, we have to assume they're figuring 25mph at 250w of power. This is technically possible according to (http://www.analyticcycling.com/ForcesSpeed_Page.html) but clearly we're in "best case scenario" land.