Originally Posted by Mothra

That's 45-miles, about 3-hours for a commuter. Definitely possible to burn through your glycogen-reserves especially on the return-trip as you probably didn't have anything to eat since lunch. Three 25-oz bottles of water in 45-miles is certainly enough liquids. If you were still sweating when you got home, then you certainly wasn't dehydrated with an onset of heat-exhaustion.

Try eating a 500-calorie meal before you take off and 200-cal/hr on the ride. Or about 6 gels on that trip. The energy-intake will allow you to do the ride faster, with intervals and sprints along the way. This improve your fitness and eventually, you'll be able to do that ride in just 2-hours.