Electric bikes advertise with a huge array of varying ranges, but what is the dominant factor is range? Electric bike range is determined by the battery, and just like other lithium battery products like laptops and cell phones the batteries performance can fluxuate based on a variety of external factors.  Extreme cold, rider weight, head winds, hills, rough terrain, tire pressure and many other factors.   But since we need to start somewhere to get the general range that a battery can produce there is baseline that we can reference to get a good indicator of range. Take a look at...
State law defines a motorized pedalcycle as a motor-driven cycle equipped with operable pedals, a motor rated at no more than 1.5 brake horsepower, a cylinder capacity not exceeding 50 cubic centimeters, an automatic transmission, and a maximum design speed of no more than 25 miles per hour.[55] Subchapter J of Publication 45 spells out the vehicle requirements in full.
There's much less of a sensation of the Electrified S2 'fighting back' once you hit 15.5mph, as well. That's helped by the automatic 2-speed gear box, although this does take some getting used to. Because its cogs are very different sizes you can end up with all sorts of cadence problems as it auto-shifts from high back to low. With practice you can avoid this, or of course you could in theory fit a second cog that's closer in size to the first.