Furnace replacement costs $2,000 to $5,400 on average for gas, electric, oil, or propane heating systems. A high-efficiency gas furnace costs $3,300 to $6,900 installed. New furnace prices depend on the system size, efficiency, brand, fuel type, and install labor.

• Installing a new furnace and ductwork costs $3,800 to $12,000.
• Replacing a new furnace and AC costs $4,000 to $10,000.

Replace a furnace when the current unit is more than 15 years old and requires frequent fixing, or when repairs cost more than half the replacement cost.

Signs a furnace is going out:

• Energy bills are increasing.
• Rooms heat unevenly.
• Fuel lines rust or system chamber cracks.
• The thermostat malfunctions.
• Furnace cycles on and off frequently or makes loud noises.
• Dust or soot buildup appears.
• Interior air smells like a gas leak.
• The gas-furnace flame is yellow instead of blue.

A furnace lasts 15 to 30 years on average, depending on the fuel type, brand, usage, and maintenance frequency. Electric furnaces typically outlast gas, propane, and oil furnaces by 5 to 10 years.

Replacing or installing a new furnace takes 4 to 18 hours on average, depending on the fuel type, size, and complexity. Extra time applies for modifying ductwork, electrical, or gas lines, adding vents or zoning, or retrofitting a larger furnace.

Options to pay for a new furnace include:

• Monthly payment financing from the supplier
• Home-improvement or bank loans
• Furnace rebates and tax credits of $100 to $500 from manufacturers, dealers, utility company, or government programs
• Credit card payment plans

The differences between a gas, oil, and electric furnace are their fuel source, heating power, and operating costs.

• Gas furnaces ignite propane or natural gas to heat and circulate air through the ductwork. Gas furnaces heat faster than electric.
• Oil furnaces burn oil from an external tank to heat and circulate air through ducts. Oil furnaces are less efficient than gas and require more maintenance, but have faster heating.
• Electric furnaces heat and circulate air with electricity or solar panels. Electric furnaces are the most energy-efficient, but have the highest operating costs.

Boilers circulate water or steam, furnaces circulate hot air, and heat pumps circulate refrigerant to provide heating.

• Boilers use natural gas, propane, electricity, or heating oil to heat and circulate water or steam through pipes to radiators in each room.
• Furnaces move centrally heated air through ducts to each room. Furnaces use gas, propane, electricity, or oil.
• Heat pumps use electricity and refrigerant to transfer outside heat from the air, ground, or water into the home.

Furnace replacement quotes are typically free. When getting furnace estimates, use this checklist:

• Compare at least three different estimates from experienced installers.
• Choose HVAC installers with certifications from:
  • North American Technician Excellence (NATE)
  • American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE)
  • National Propane Gas Association (NPGA)
  • State-certified natural gas journeyman training programs in gas fittings
• Avoid choosing the lowest bids that signal low-quality work.
• Select licensed, insured, and bonded HVAC contractors.
• Review their ratings on HomeGuide and Google.
• Request copies of estimates, plan diagrams, heating-load calculations, equipment orders, permits, warranties, and contracts.
• Verify the estimates include material, labor, equipment costs, and the installation schedule.
• Set up a payment schedule. Never pay in full upfront.
• Ask the questions below before signing a contract.

When looking to hire the best furnace contractor near you, ask them the following questions:

• How many furnaces have you installed?
• Can you give me references from past jobs?
• What’s the efficiency rating of this furnace? Do you recommend high-efficiency systems?
• Does this furnace qualify for tax credits or rebates?
• Is this furnace compatible with my existing ductwork, wiring, and thermostat?
• Do you have a warranty for repairs?
• Do you offer a maintenance plan?
• Will you use the Manual J load calculation to size my new furnace?
• How much are permits and inspections?
• Are all labor, materials, old furnace disposal, and cleanup fees included in this estimate? What other costs apply?
• Are any ductwork modifications necessary?
• Will I need electrical or gas line work?
• Do you subcontract the electrical work?
• Do you test my ducts for leaks?
• How long will the installation take?
• Do you offer financing?
• What’s your payment timeline?
• Do you follow all building code requirements?
• Do I need a backup heater for this system?

Furnace installers don’t expect a tip and it's not customary. However, tipping $10 to $20 per person is a nice gesture when installers do a great job.