Oil, natural gas, coal, wood, pellet and corn are some of the home heating fuels used in modern boilers (also known as furnaces). Gas or oil fired furnaces will typically last 18 years, while a hot water or steam boiler may last as long as 30 years. Thinking of replacing your old boiler or steam heating system? New closed-system boilers are compact, quiet, and can achieve up to 95 percent fuel efficiency. New boilers offer zone heating, and some provide instant and almost unlimited hot water. If you love steam heat, check out our guide to boilers and suppliers.