Furnace replacement in Naperville, IL
The short answer
A furnace replacement in Naperville, IL runs $5,000–$9,000 installed: about $5,000–$7,000 for a standard 80% AFUE furnace, and $6,300–$9,000 for a 95%+ high-efficiency unit with new PVC venting. Most swaps take one day. The price covers Manual J sizing, a ductwork check, removal of the old furnace, any City of Naperville permit the job needs, and a combustion analysis at startup.
Written by Jenna Fortman, Owner of FortHouse Heating & Cooling. Installed by EPA 608 and NATE-certified technicians.
What does furnace replacement cost in Naperville?
| Option | AFUE | Installed price | Venting and scope |
|---|---|---|---|
| Standard efficiency | 80% | $5,000–$7,000 | Uses the existing metal flue |
| High efficiency | 95%+ | $6,300–$9,000 | New PVC venting and a condensate drain, included |
| Ductwork changes | — | +$800–$2,500 | Only if the existing ducts can't carry the new furnace's airflow |
The gap between the two tiers is mostly venting. A 95% furnace's exhaust runs cool enough to need sealed PVC pipe instead of the metal flue an 80% furnace uses, plus a drain for the condensate. Whether the lower gas bills pay that back depends on the house and how long you'll stay, so we run that math at the sizing visit.
Repair or replace: how do you decide?
Multiply the furnace's age by the repair cost. Over $5,000, replacement usually wins. Separately, if one repair costs more than half of a new furnace, replace. A cracked heat exchanger or a second repair in the same season pushes toward replacement even when the math is close.
| Furnace age | Repair quote | Age × cost | Verdict |
|---|---|---|---|
| 8 years | $400 | $3,200 | Repair |
| 12 years | $450 | $5,400 | Close — check the 50% rule too |
| 20 years | $300 | $6,000 | Replace |
What happens on installation day?
Before install day
Sizing visit
A Manual J load calculation on the house and a check of the existing ductwork, so the new furnace fits the house instead of copying the old unit's size.
Written quote
Furnace tier, venting, and any duct work, priced in writing before any work starts.
Permit check
A like-for-like swap needs no permit in Naperville. If the job goes beyond that, we pull it with the City, the same office on both sides of the county line. A home in unincorporated DuPage or Will County with a Naperville address goes through that county instead.
Install day
Old furnace out
Disconnected, removed, and hauled away. Removal is in the price.
New furnace in
Set, with the venting, gas line, and combustion air done to code.
Startup and combustion analysis
Measured combustion readings at startup, written down and left with you.
After
Inspection, if permitted
When the job needed a permit, we schedule the City's inspection. You don't have to call anyone.
What does a finished FortHouse furnace install look like?
Why is furnace replacement different in Naperville?
City permit, not county
Naperville straddles the DuPage–Will county line, but inside city limits the permit comes from the City of Naperville either way, not from either county; an unincorporated address with a Naperville mailing address goes through its county instead. The City's own permit guide says a like-for-like furnace swap needs no permit. When a job changes the furnace's type or size, or adds new venting or duct work, we check with the City's Building Services before quoting and pull the permit if it's required.
City-owned electric
Naperville is one of a few dozen Illinois communities that runs its own electric utility instead of buying power through ComEd. If a furnace job needs the power cut at the meter or new electrical service, that's coordinated with the City's Electric Utility, not ComEd's outage line.
Six decades of housing
The housing stock spans six decades in the same zip code: a split-level near the Historic District built well before modern venting codes, a newer build in a subdivision like Ashwood Park. We run a Manual J load calculation and check the ductwork on every replacement instead of matching whatever the last furnace happened to be.
Questions Naperville homeowners ask
How much does furnace replacement cost in Naperville, IL?
$5,000–$9,000 installed. A standard 80% AFUE furnace runs about $5,000–$7,000 and vents through the existing metal flue. A 95%+ high-efficiency furnace runs about $6,300–$9,000, including the new PVC venting it needs. If the ductwork has to change, that adds $800–$2,500, quoted separately in writing.
Do I need a permit to replace a furnace in Naperville?
Not for a like-for-like swap: the City of Naperville's permit guide says no permit is required for an in-kind furnace replacement. If the job changes the type or size of furnace, or adds new venting or duct work, we check with the City's Building Services before quoting and pull the permit if it's needed. Inside city limits, it's the City on both sides of the DuPage–Will county line; unincorporated addresses go through their county.
How long does furnace replacement take in Naperville?
Most standard swaps finish in one day: removal, the new furnace, and a combustion analysis at startup. Switching to a high-efficiency furnace that needs new PVC venting, or changing the ductwork, can add a half to a full day.
Is furnace replacement the same as furnace installation?
Yes. A furnace replacement is a furnace installation where the old unit comes out first. The Manual J load calculation runs the same either way, sized to the house you have now rather than whatever the furnace being replaced happened to be.
Does Naperville's own electric utility affect a furnace replacement?
Only if the job needs the power cut at the meter or new electrical service. Then it's coordinated with the City of Naperville's Electric Utility rather than ComEd, which is a different process than in most surrounding suburbs. We handle that as part of the job.
When should I replace my furnace instead of repairing it?
Replace when a repair costs more than half of a new furnace, or when the furnace's age times the repair cost tops $5,000. ENERGY STAR recommends a professional evaluation once a furnace passes 15 years. If the math still favors a fix, Naperville furnace repair is the better call.
Can you replace the furnace and the AC at the same time?
Yes, and it often costs less per system because the labor and sizing work overlap. We still check each system on its own first, so a healthy AC doesn't get replaced just because the furnace failed. See AC installation in Naperville for the cooling side.
Sources
Prices are FortHouse's own published installed ranges, last updated October 6, 2026. Your written quote follows a home visit, not a phone call.
- City of Naperville — Guide to Building Permits
- ENERGY STAR — when to replace heating and cooling equipment
- EPA — Section 608 technician certification