Start Here: What Actually Matters
Most homeowners focus on brand names and price. The three things that actually determine whether you'll be happy with your furnace five years from now are: efficiency rating (AFUE), staging (single/two-stage/modulating), and proper sizing. Brand matters less than getting these three right.
Step 1 — Choose Your Efficiency Tier
80% AFUE (standard efficiency): Vents through a metal flue pipe. Lower upfront cost. Makes sense if you have an existing metal flue you want to reuse, or if your home is well-insulated and you run the furnace less. Installed cost in Chicago typically runs $3,500 to $6,500 depending on brand and size.
90–96% AFUE (mid-high efficiency): Condensing furnace — vents through PVC pipe. Extracts more heat from combustion, so exhaust gases are cooler and wetter. Requires a condensate drain. Most popular tier in Chicago. Installed cost typically $5,500 to $9,500.
97–99% AFUE (premium efficiency): Modulating furnaces like the Lennox SLP99V or Carrier Infinity 98. Maximum efficiency, quietest operation, most even heat. Installed cost typically $9,000 to $13,000+. Payback period vs. a 96% unit is long — you're buying comfort as much as efficiency.
Chicago note: The city's cold winters mean your furnace runs a lot. Higher AFUE pays back faster here than in milder climates. A 96% vs. 80% furnace can save $200 to $400/year on gas depending on home size.
Step 2 — Choose Your Staging
Single-stage: On or off. Runs at 100% capacity every time. Least expensive. Works fine in smaller homes or homes with good ductwork. Can cause temperature swings and tends to be louder.
Two-stage: Runs at ~65% capacity most of the time, 100% on the coldest days. More efficient, quieter, more even heat. The sweet spot for most Chicago homes. Worth the modest price premium over single-stage.
Modulating: Adjusts output continuously from ~40% to 100%. The most comfortable option — virtually no temperature swings, very quiet, highest efficiency. Best paired with a communicating thermostat (like the Lennox S40 or Carrier Infinity). Significant price premium; best suited for larger homes or homeowners who prioritize comfort.
Step 3 — Get the Right Size
Furnace capacity is measured in BTUs (British Thermal Units). Common residential sizes range from 40,000 to 120,000 BTU. Bigger is not better — an oversized furnace short-cycles (fires and shuts off repeatedly), wastes energy, and wears out faster.
Proper sizing requires a Manual J load calculation — a room-by-room analysis of your home's heat loss based on square footage, insulation, windows, ceiling height, and local climate data. Any reputable HVAC contractor will perform this before recommending a size. Be wary of contractors who size by square footage alone.
See our Furnace Sizing Guide for a full explanation.
Brand Comparison
Lennox: Premium tier. Best-in-class efficiency on the SLP99V (up to 99% AFUE). Strong warranty (10-year parts, 20-year heat exchanger with registration). Requires authorized dealer installation. D's Air & Heating is a Lennox Premier Dealer.
Carrier: Premium tier. Infinity series (96–98% AFUE) is excellent. Strong communicating system integration with Infinity thermostats. Widely available parts and service.
Goodman / Amana: Value tier. Owned by Daikin. Solid reliability at a lower price point. Amana offers a lifetime heat exchanger warranty on select models. Good choice for budget-conscious buyers who don't need top-tier efficiency.
Ruud / Rheem: Mid-tier. Reliable, widely serviced. Good warranty terms. Less differentiated at the top end compared to Lennox or Carrier.
Sinclair: Value tier. Competitive pricing. Good for rental properties or budget replacements.
Variable-Speed Blower Motors
Separate from staging, the blower motor can be single-speed, multi-speed, or variable-speed (ECM). A variable-speed ECM motor ramps up and down slowly, uses significantly less electricity (up to 75% less than a single-speed motor), runs quieter, and provides better air filtration because it moves air continuously at low speed between heating cycles.
If you're spending money on a high-efficiency furnace, pair it with a variable-speed blower. The electricity savings alone often justify the cost difference.
What's Included in an Installation
A complete furnace installation should include: removal and disposal of the old unit, installation of the new furnace, connection to existing gas line (with leak test), connection to existing ductwork, new flue venting (PVC for condensing, metal for 80%), condensate drain line (condensing only), new thermostat wiring if needed, startup and commissioning, and a walkthrough with the homeowner.
Permits are required in Chicago and most suburbs. A licensed contractor pulls the permit and schedules the inspection. If a contractor offers to skip the permit to save money, walk away.
Installed Cost Ranges in Chicago (2024–2025)
- 80% AFUE, single-stage: $3,500 to $6,500
- 96% AFUE, two-stage: $6,000 to $9,500
- 98–99% AFUE, modulating: $9,000 to $13,500+
Prices vary based on brand, BTU capacity, ductwork modifications, and whether a new thermostat is included. Get at least two quotes and make sure both include the same scope of work.
Warranties: What to Look For
Most manufacturers offer a 10-year parts warranty with registration (5 years without). Heat exchanger warranties range from 10 years to lifetime. Labor warranty is provided by the installing contractor — typically 1–2 years. Ask specifically about the heat exchanger warranty; it's the most expensive component to replace.
Rebates and Financing
ComEd and Nicor Gas both offer rebates for high-efficiency furnace installations in Illinois. Rebate amounts change annually — check their current programs before purchasing. Federal tax credits (25C) may also apply for qualifying high-efficiency equipment. Ask your contractor to confirm eligibility before installation.
D's Air & Heating offers financing through approved lenders. Ask about current terms when you request your estimate.
Bottom Line
For most Chicago homes: a 96% AFUE, two-stage furnace with a variable-speed blower is the sweet spot. It delivers meaningful efficiency savings over an 80% unit, costs significantly less than a modulating furnace, and provides noticeably better comfort than a single-stage unit. Pair it with a smart thermostat and you'll have a system that performs well for 15–20 years.