If you're going to go with a hub motor kit, make sure your bike has a steel frame, especially if you plan on using a front hub motor (and use torque arms!). 36v15ah on a 500w motor will be more than adequate for a 10 mile roundtrip commute (assuming your "hills" are like what I mean by "hills"). You'll be cruising along at 20ish without much pedaling. You could go bigger and get a 600-1000watt motor and bump up to 48v, cruising along in the high 20's/30's without pedaling. I considered myself in shape before starting my 15 mile round trip commute by ebike and I still lost 10 pounds.