I am thinking about buying a house that has an OLD one. How much does a new one cost if it has to be replaced? How much do they cost to run vs. traditional furnaces? Thanks for any information or cautions.
Some of those old boilers with their cast iron heat exchangers are still just fine -- as far as safety goes. Your gas utility likely has a free or low cost service where they will test for fume leaks. The problem is that they get so gummed up that they can be as little as 40% efficient in their use of fuel. We just replaced a 35 year old boiler in an 18-suite apartment building for efficiency reasons. We did not go for a high efficiency boiler at a cost of $20,000 but chose a medium efficiency 82% efficient RBI boiler at half that cost and have calculated that, even if natural gas remains at $7.50/gigajoule, we will be money ahead midway through the 7th winter. Be sure to shop around though. We found differences of over 35% in quotes for installations of boilers with nearly identical specifications and uniformly excellent reputations.
A new boiler costs about $3,000-5,000 for a standard efficiency boiler. A high-efficiency model will run one thousand to three thousand dollars more while furnaces run about $5-$7k. That cost is quite variable depending on if there is existing ductwork or if there are complications in the installation process. Another option you may want to consider is a heat pump system which typically is one of the most efficient ways to heat AND cool your home. Each home is different and for an exact price it would be wise to have a contractor or professional visit your home for an estimate.
