Heating
Furnace installation and replacement
A furnace replacement should start with a heat-loss calculation, not the old unit's label. The installer then chooses an efficiency level (80% or 90%+ AFUE), plans venting and condensate, and verifies gas pressure, temperature rise and combustion before the permit inspection.
- Licensed local HVAC contractor
- Diagnosis and price before work
- Same-day appointments when a local contractor has an opening
- Free to call, no obligation
Moving from an 80% to a 95% furnace means new PVC venting and a condensate drain, which affects where the unit can go. In mild climates the higher efficiency may take many years to pay back; in cold climates it usually pays off much faster.
Your ductwork, blower and thermostat need to match the new furnace. Variable-speed and two-stage models run quieter and more evenly, but only if the ducts are sized for them.
Furnace Installation & Replacement at a glance
- Category
- Heating
- Urgent service
- Usually scheduled
- Who does the work
- An independent, licensed HVAC contractor
- Quote
- Given after diagnosis, before work starts
Signs you need furnace installation & replacement
- Furnace 15–20 years old
- Cracked heat exchanger reported
- Uneven heat from room to room
- Frequent repairs in recent winters
- Rising gas bills
What the technician does
- 1
Heat-loss calculation
Sizing is based on the house, not the old furnace, which was often oversized.
- 2
Choose efficiency and staging
Single-stage, two-stage or modulating; 80% or high-efficiency condensing.
- 3
Install
Old unit removed, venting and gas line adapted, condensate routed, ducts sealed at the plenum.
- 4
Combustion test and permit
Gas pressure, temperature rise and flue gases measured; the local mechanical permit is inspected where required.
What affects the cost
Prices are set by the contractor after diagnosis. These are the factors that move the number most:
- AFUE rating and staging
- Venting changes (chimney liner or new PVC)
- Ductwork and return-air modifications
- Whether AC coil and condenser are replaced at the same time
- Permit fees and utility rebates
Safe to check yourself
- List rooms that run cold
- Check for gas-utility rebates
- Ask bidders whether they'll pull the permit
Leave to a pro
- Gas line or venting work of any kind
- Reusing an unlined masonry chimney for a new furnace without inspection
Furnace Installation & Replacement FAQ
Is a 95% furnace worth it?
In cold climates with long heating seasons, usually yes. In warm climates where the furnace runs little, an 80% model or a heat pump may make more financial sense.
Can I replace the furnace and keep my AC?
Yes, if the existing AC and coil are in good shape and compatible. If the AC is near the end of its life, replacing both together often saves labor and ensures a matched system.
Do furnace replacements need a permit?
In most U.S. jurisdictions, yes. A mechanical permit and inspection confirm safe gas piping, venting and combustion. The licensed contractor normally pulls it.
What does AFUE mean?
AFUE (Annual Fuel Utilization Efficiency) is the share of fuel a furnace turns into heat. An 80% AFUE furnace loses about 20% up the flue, while a 95% furnace loses about 5%.
What is a two-stage or modulating furnace?
A two-stage furnace runs at low fire most of the time and high fire on the coldest days; a modulating furnace adjusts in small steps. Both run longer, quieter cycles with more even temperatures.
Can a new furnace use my old chimney?
An 80% furnace can often vent into a properly lined chimney. High-efficiency furnaces vent through PVC pipe instead, which frees the chimney but requires a condensate drain.
How long does furnace installation take?
A straight replacement usually takes one day. Venting changes, ductwork modifications or adding AC at the same time can extend it to two days.
Should I replace a furnace with a heat pump?
In mild and mixed climates a heat pump often lowers total energy costs and adds efficient cooling. In very cold areas, a dual-fuel system keeps a furnace for the coldest days.
Last reviewed . General information, not a diagnosis of your system.
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