As of 2015, professionally done annual maintenance for a gas furnace costs between $80 and $130. The cost can be as little as $25 in parts if an owner can do the work himself.
This routine maintenance is typically done annually and keeps a furnace in optimum running condition. Should a furnace break down, the repair cost can be substantially higher. According to HomeAdvisor, the national furnace repair cost in 2015 averages $200, ranging from $125 to $350 per repair. Though gas furnaces have an estimated lifespan of 20 to 30 years, it is suggested a furnace be replaced after 15 years.