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 appliance