Simple furnace repairs often cost between $100 and $600, while more complex repairs can cost $1,000 to $2,500 or more, as of 2015. Oil furnace maintenance is generally a bit more expensive than gas furnace maintenance.
Most people can expect to spend between $300 to $400 for routine furnace repairs. However, unless the cause of the problem is known, it can be difficult to estimate how high the repair cost might run. In some cases, a small, inexpensive part might need to be replaced. In other cases, the structure of the furnace itself might be damaged beyond repair, rendering the entire system unsalvageable.