As of 2015, gas boilers are manufactured by U.S. Boiler Company, Weil-McClain and Crown Boiler Company. Each manufacturer makes several models and sizes of gas boilers.
U.S Boiler Company manufactures five models of gas boilers in both compact and standard sizes. Two models are made for homes with existing chimneys, while other models have top or side venting. All models have a cast iron heat exchanger. Gas boilers manufactured by U.S. Boiler Company are rated between 82 and 85 percent efficiency and have limited lifetime warranties.
Weil-McLain manufactures both residential and commercial gas boilers. The company makes wall-mounted and free-standing boilers in a variety of sizes. Weil-McLain offers gas boilers with cast aluminum, cast iron and stainless steel fire tube heat exchangers. Two models of Weil-McLain gas boilers are Energy Star certified. Various venting options are available on Weil-McLain boilers, such as top-venting, side-venting and downdraft.
The Crown Boiler Company manufactures seven models of residential and five models of commercial gas boilers. Boilers are available in several sizes and in models that are free-standing and wall-mounted. Crown Boiler Company gas boilers are available with several venting options, with two models manufactured specifically for homes with existing chimneys. Two models of Crown Boiler Company gas boilers are Energy Star certified.