Boilers are a common heating device for most homes in the US. The warmth generated by boilers through an intricate system has made the lives of millions in the US comfortable. Boilers have become a necessity in the US and there is hardly a household that does not possess these gadgets. Boilers heat water, supplying either hot water or steam for the purpose of heating.

Steam is disseminated through pipes to steam radiators, while hot water can be supplied by means of baseboard radiators or radiant floor systems, or can heat air with the help of a coil. Steam boilers function at a higher temperature than hot water boilers, and are essentially less effective. But thanks to modern technology, high-efficiency forms of all sorts of boilers are presently obtainable.

A central boiler's effectiveness is determined with the help of annual fuel utilization efficiency (AFUE). Prevailing laws in the US make it mandatory for boiler manufacturers to provide information about their AFUE to consumers, so that they can compare the heating effectiveness of different models. AFUE is an indication of an appliances effectiveness through a particular year. In precise terms, AFUE is the ratio of heat output of the boiler in contrast to the entire energy used by a boiler.

Electric boilers are highly efficient, but the high cost of electricity in the US deters consumers from using them. The AFUE rating for an all-electric boiler is between 95% and 100%. A boilers efficiency can also be gauged, apart from the AFUE, by the characteristics of its equipment. Mid-efficiency heating systems are characterized by a natural draft that generates a supply of combustion gases, a continuous pilot light, and a heavy heat exchanger.

High-efficiency boilers are marked by an exhaust fan that controls the flow of combustion air and combustion gases more accurately, an electronic ignition that ensures the absence of a pilot light, a compact size, a lighter weight to diminish cycling losses, and a small-diameter pipe.