The solar bag takes a little while to warm the water up, to speed this up we warm water on camp fire or grill and mix with cold water. Sportmans guide sells a couple complete kits for under $50. I usually bring a few gallons of water or a couple of 5 gallon buckets and fill them a nearby gas station or a fresh spring. Nothing like a ice cold shower that makes your teeth chatter or takes your breath away but its does make you feel fresh and wakes you up if you don't warm the water.