Distribution is one of the costs. For discussion lets call it 10% of your power bill (someone can find real numbers, but that will work if like me you are too lazy to look it up). However there are other costs - you pay to maintain the backup systems that are not in use. I know of a generator installed in 1920 connected to a coal boiler built in 1880 - this horribly inefficient system (by modern standards) takes about 12 hours to turn on when needed - but gets regular maintenance including pressure testing just to be sure it works for the one time every 5 years when all the other backup systems are not enough - that is not free and you pay for the costs even though you rarely get power from it. (well you probably live in a different part of the world and so could not get power from it - but there is something like it that you are paying for)