The answer to that depends on the type of boiler you have. Old
commonly last 35 to 50 years. We have seen 80-year-old boilers still in service. These systems were originally fired with coal. They were often converted to oil, and later changed to gas.
Some old boilers were designed as steam systems, and have been converted to hot water.
older steel boilers
typically lasted 20 to 35 years, although most of those are near the end of their life now.
have life expectancies of 15 to 25 years. Some fail as early as 10 years into their life, and there are always those that do better.
Condensation causing rust is the big enemy of both the steel and copper-tube boilers.
No one knows for sure how well the newer
s are going to perform over the long term. Heat exchangers are typically copper, stainless steel or cupro-nickel alloys. Some difficulties have been experienced with the copper heat exchangers on some systems. These are being replaced with stainless steel as they fail.