4km isn't far, so the smaller battery of the Gain won't matter. It is really conceived of however as a bike for road enthusiasts who just want a little help uphill, and otherwise intend to be riding above 25kph under their own power. Not as a commuting platform. I like the stealth look and idea. For commuting, lights, rack and fenders are essential. You should be able to add these to the Gain. Running the lights off the main battery will probably not work. (So just use rechargeable detachable lights, or get a dynamo hub.) If you want to go on long road rides for fitness and/or fun (in addition to commuting) then this could be a nice choice. If you just want to accomplish your short commute, you can do that for less money with some other bike that will have more range and power, and include the essential lights, rack and fenders. Nothing will come