Power-assist: Also known as pedal-assist bikes, these are the bicycle equivalents of hybrid cars: they're designed to be pedaled quite a lot of the time and electrically powered either when you're tired or when you feel like a bit of electric help (when you're going up hill, for example). Unlike full-power bikes, they don't have hub motors; instead, there's a separate electric motor mounted near the rear wheel and driving it either through the gear sprocket or simply by pressing against the rear tire. Where a hub motor is difficult or impossible to pedal without any power (because you're effectively turning it into a generator), power-assist motors turn easily with little or no resistance when you pedal. That gives power-assist bikes much greater range than hub-motor ones (as much as 80–145km or 50–90 miles).
“Changes in production and consumption patterns are a crucial element of the sustainability agenda. Communication between product developers and users, and user integration in product development, can serve as a means for organizational as well as individual learning processes, resulting in sustainable product development. [...] Improved methods, such as INNOCOPE (innovating through consumer-integrated product development), tested in this study with a cycle manufacturer and resulting in a new product, a pedelec, are needed for effective communication, activating consumers and enabling them to promote sustainability goals. Through co-operative product development processes key factors facilitating and obstructing the adoption of sustainable innovations may be identified. Such processes can enhance the emergence and diffusion of sustainable product innovations and different forms and bodies of knowledge can be combined. Integrating users' contextual everyday knowledge of the product with the technical knowledge of companies may lead to mutual learning, technical innovations and changes in consumer behaviour.” (Hoffmann, 2007).

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.