If the bike fits your body, and is properly designed vis a vis its geometry, you will be able to exert enough power to get up any rideable hill as long as the bike has low enough gearing. Some well known and popular bikes like the Brompton have quite high gearing as delivered - bottom end of 45 inches. If you are strong and the hills aren't too terrible this might be low enough, but you'd be better of with low gears in the thirties. I think my mountain bike goes down to about 28 inches in its lowest gear. My folder only down to 38. I can climb steep hills on it, but it would be no good for touring in the hills.