Most water heaters available in the United States are made by only a few large companies. Depending on the brand, quality and features, such as warranty, may vary. Many people on forums comment that all water heaters are generally similar in performance, saying appearance is often the only major difference between two names.
Regardless, it's a good idea to check out what users and experts have to say about specific models or brands before you make a decision. Websites like Do It Yourself.com host comments from a lot of individuals and dealers talking about product and brand specifics. Just type in a search phrase - for example, "best water heater" or "GE water heater" - to find out what's been said.
Some notable water heater manufacturers include:
American Water Heater Company (AWHC) - A well-known manufacturer of residential and commercial gas and electric water heaters, this company is credited with creating the first flammable-vapor-resistant water heater. "Flame Guard," as they dubbed it, became mandatory for almost all gas water heaters in the United States just three years later. Brands under American Water Heater Co. include Whirlpool, sold through the mass-merchant channel; American PROLine, sold through the plumbing wholesale channel; and U.S. Craftmaster, sold through the retail channel.
Rheem Water Heating - Manufacturing water heaters since the 1930s, this company focuses on their award-winning tankless water heaters. The models come natural gas or propane fueled, with the option for placing them indoors or out. Conventional storage or solar water heaters are also available. They are the makers of water heaters branded GE (sold exclusively at Home Depot), Ruud and Richmond. A popular model seems to be the electric Rheem Marathon, which has been mentioned on several forums and called a selling point for a home.
A.O. Smith - Also in business since the '30s, A.O. Smith is known for manufacturing some of the highest water heater efficiency units on the market, particularly with their Conservationist series. Their products run the gamut of electric, gas, pump and boiler units. A.O. Smith water heaters can be found under brand names such as Reliance, Kenmore, Maytag and State.
The American Council for an Energy-Efficient Economy has compiled water heater efficiency ratings , sorting by fuel type and including brand and capacity.