Selecting a home water boiler is based on individual needs that revolve around size, efficiency, fuel source and venting requirements. Water boilers use wood, natural gas, electricity, propane or oil to produce hot water, which heats the home. The fuel source plays an important role in selecting an appropriate boiler.
An important factor that drives boiler selection is the Annual Fuel Utilization Efficiency, or AFUE, rating. The AFUE rating indicates how effective the boiler is at converting fuel into heat. High-efficiency boilers have an AFUE rating of 85 percent or better. Many high-efficiency water boilers also have the ENERGY STAR certification.
When selecting a water boiler, it is important to ensure the boiler is the right size for the home. The capacity of the boiler is measured in British Thermal Units or BTUs. Every home has a distinct BTU requirement that is calculated based on the number of windows and doors, the geographical location, the quality of the home's insulation and climate. For example, 2,000-square-foot homes located in moderate climates require boilers capable of producing 70,000 BTUs. A BTU calculator is useful for determining what size boiler is required.
The venting system is another factor that drives boiler selection. Chimney-vented boilers use a chimney to exhaust, whereas power- or direct-vent boilers utilize internal fans to expel exhaust via a side wall or roof.