This on-demand water heater from Coleman is great for campers, remote cabins, or just emergency preparedness. The Hot Water On Demand heater can heat water to over 100 degrees in less than five seconds. There’s a rechargeable battery to pump the water that is charged with AC power or by a car power outlet. The heater uses 16.4 oz propane canisters, or it can be converted to operate with a bulk propane tank. You’ll heat about 40 gallons of water with a single battery charge and canister. The Hot Water on Demand heater costs about $250. It’s currently out of stock at Coleman’s online store, but it’s available at Amazon and at various brick-and-mortar retailers like REI.