Another +1 on Machka.
If you run out of carbs during a ride, you're going to bonk.
I've seen anywhere from 60 to 120 minutes quoted as the amount of time before you need supplemental carbs, but that depends wholly on the level of your carb reserves that day, how hard you work out and probably on your particular genetics.
I both gotten lucky (ridden a long time without enough calories), and bonked early (when I brought food, but just not enough), so for me I don't like to push it. If I'm only going to be out for an hour, I might do it with just water (though I always have gel on the bike if I need it), but anything longer (which really covers most of my rides), I have a bottle of sports drink, and generally something solid like a clif bar or a few newtons.
I'm generally drinking every fifteen minutes or so, simply because I don't see the point of going into "carb debt" if I'm planning on replacing all of them at the end anyway. I can always cut down what I drink later on, but after you bonk, all the sugar in the world isn't going to make you happy again (it *will* get you home...)
I started with diluted gatorade, and it was a non-starter for me. I tried on a couple of rides, and couldn't force myself to get enough down, and anything more than a little solid food makes my stomach upset. Not a recipe for a nice ride.
Last year I switched to accelerade (blue raspberry!), and that's something I can drink a lot of on an ongoing basis. The real sports drinks are pricey, but the difference was pretty astounding.
I'll use a gel if I'm feeling close to out of energy, but I don't tolerate them that well, so I stick to the sports drink.
I'm probably pretty close to 250 cal/hour, which includes 22 oz of sports drink and additional water. I've gotten so I can generally come pretty close to replacing sweat,
but it's a good idea to weigh yourself before and after a ride so you can see how much you need to replace and whether you're drinking enough.
Oh, one other thought - sports drinks are generally absorbed better than water.