You can compare propane water heaters by researching different models and comparing features that best suit your specific needs. As of 2015, Lowe's states that the average propane heater heats between 40 and 100 gallons of water and uses up to 50 percent less energy than electric heaters.
To compare propane water heaters by their features, you must first determine what you need from the product and select the product that fits best. For example, the Rheem model XP5oTo6PV42Uo is a 50-gallon tank with enough hot water for a family of five. Compare that to the Westinghouse model WGRo6oLPo76, which is a 60-gallon tank that may provide hot water for a group of five or more. Westinghouse is also noted for being stylish and corrosion-resistant, while the Rheem model boasts an Energy Star qualification as well as a warranty.
Compare propane water heaters by reading customer reviews to help you find the right product. For example, Home Depot's website offers both Rheem and Westinghouse propane water heaters. The Rheem heaters tend to be on the cheaper side of the two and maintain a 4.5 review rating, while Westinghouse is more expensive and has zero customer feedback as of February 2015.