Gas furnaces still heat the majority of older Eastside homes, but the share of new installations going to furnaces is shrinking every year. For the right home in the right configuration, a high-efficiency gas furnace is still the correct answer. For the wrong home, it is a fifteen-thousand-dollar mistake that gets harder to undo each year as natural gas prices climb and electrical rates stay flat.
We install gas furnaces every week. We also walk away from furnace quotes when a heat pump is clearly the better long-term answer for the home in front of us. The job of an honest HVAC contractor is to give you the comparison data, not to upsell whatever has the highest margin this quarter. This page covers when a furnace is the right choice, what a quality installation actually includes, and what you should expect to pay on the Eastside in 2026.
When a Gas Furnace Is the Right Choice
Furnaces continue to make sense in three scenarios on the Eastside. Outside of these scenarios, a heat pump is almost always the correct recommendation.
1. Insufficient electrical service for a heat pump conversion
A central heat pump adds 40 to 50 amps of continuous electrical load to a home. A home with a 100-amp service panel that is already supporting an electric range, electric water heater, and electric dryer often cannot accept a heat pump without first upgrading the electrical service to 200 amps. The combined cost of a panel upgrade plus a heat pump conversion can exceed $20,000. In that situation, replacing the existing gas furnace with a high-efficiency model and leaving the electrical service alone is sometimes the most defensible decision.
2. Dual-fuel hybrid configurations
A hybrid system pairs a heat pump (for primary heating and all cooling) with a small gas furnace as the supplemental cold-weather backup. The system uses the heat pump down to about 35 degrees Fahrenheit, then switches to the gas furnace below that threshold. This configuration is common in homes where the homeowner wants the cost efficiency of a heat pump for the bulk of the heating season but is unwilling to give up gas backup for the rare extreme cold snap. PSE has historically offered rebates for properly configured dual-fuel systems.
3. Older homes with existing high-quality gas infrastructure
If your home already has a properly sized and well-located gas furnace plenum, an existing high-pressure gas line, intact ductwork in good condition, and the chimney or sidewall vent already in place, the cost differential between replacing the furnace versus converting to a heat pump can be significant. Reusing existing infrastructure usually tips the math in favor of furnace replacement, especially if the homeowner plans to sell within five to ten years.
The honest comparison
Operating cost: on current PSE rates, a 95% AFUE gas furnace costs roughly the same per delivered BTU as a 9 HSPF heat pump for the average Eastside winter. As natural gas rates increase and electrical rates stay relatively flat, the gap widens in favor of heat pumps over a 15-year horizon. Upfront cost: a furnace installation runs roughly half the price of a comparable central heat pump installation, before rebates. After PSE and federal rebates, the gap narrows significantly. We provide both numbers on every comparable quote.
What a Standard Furnace Installation Includes
A complete gas furnace installation involves substantially more than swapping the box in your utility closet. Our flat-rate quotes include every line item below as standard scope. Anything outside this list is documented and approved in writing before work begins.
- Site visit, Manual J load calculation, and written flat-rate quote
- Mechanical permit pulled with WA L&I or the city electrical inspector where applicable
- Removal and proper disposal of the existing furnace, including reclamation of refrigerant if a paired AC condenser is also being removed
- Installation of the new furnace, sized per load calculation, with the correct gas valve, ignition system, and combustion blower
- Gas line inspection and sizing verification — undersized gas lines are upgraded as part of scope when required
- Venting installation (PVC for condensing 90%+ AFUE, B-vent for non-condensing 80% AFUE) with proper slope, support, and termination clearances
- Condensate drain installation and trap, with proper neutralization where required by jurisdiction
- Combustion air supply verified and corrected if undersized for the new unit
- Electrical disconnect, dedicated 120V circuit, and service switch all verified and corrected as required
- New thermostat installation (programmable or smart, your choice) with proper wiring
- Ductwork inspection and repair of accessible duct leaks at the plenum and major joints
- Startup, combustion analysis, and gas pressure measurement with documented printout
- Permit inspection scheduling and any corrections required by the inspector
- Full removal of all packaging and old equipment
- One-year workmanship warranty on installation work; manufacturer warranty registered in your name
Furnace Sizing — Why Bigger Is Worse
The most common mistake in furnace replacement is oversizing. A furnace that is too large for the home short-cycles: it heats the air quickly, hits the thermostat setpoint, shuts off, then restarts a few minutes later. Short-cycling reduces efficiency, increases wear on the ignition and blower, and creates uneven heat distribution and uncomfortable temperature swings.
The right answer is a Manual J load calculation. Manual J is the industry-standard procedure for computing the actual heating and cooling load of a home based on its insulation, window area, orientation, infiltration rate, and local climate data. A correctly sized furnace operates in longer cycles at a lower BTU input than the home's worst-case load, producing steadier comfort and longer equipment life. We perform Manual J calculations on every furnace installation as standard scope, not as a costly add-on.
Most existing furnaces in older Eastside homes are oversized by 25% to 60% relative to the home's actual load. Newer construction tends to be closer to correctly sized but is frequently still slightly oversized. Right-sizing a replacement furnace often allows downsizing by one or two capacity tiers (from 100,000 BTU to 80,000 BTU, for example), which reduces upfront cost and improves comfort simultaneously.
AFUE Efficiency Tiers and What to Choose
AFUE — Annual Fuel Utilization Efficiency — measures the share of gas energy converted to usable heat over a full season. Modern furnaces fall into clear efficiency tiers, each with different installation requirements and operating economics.
80% AFUE — Non-condensing standard
The minimum legal efficiency for new installations in Washington. Vents through a metal B-vent or masonry chimney. No condensate produced. Cheapest to install ($1,000 to $1,500 less than condensing). Operating cost is about 18% higher than 95% AFUE over a heating season. Appropriate when the existing venting infrastructure is in place, the homeowner plans to sell within 5 years, or the home does not have a path for condensate drainage.
90-95% AFUE — Standard condensing
The mainstream installation tier. Vents through PVC pipe through a sidewall or roof penetration. Produces condensate that must drain to a floor drain, condensate pump, or neutralizer. Single-stage or two-stage operation. Eligible for PSE rebates and the federal IRA Section 25C tax credit.
95-98% AFUE — Premium modulating
The top tier. Variable-speed inverter blower, modulating gas valve, and full BTU range modulation from 30% to 100% of rated capacity. Highest efficiency, quietest operation, best comfort. 20% to 30% higher installation cost than standard condensing. Operating cost savings vs. 95% AFUE are real but modest — typically $40 to $90 per heating season on the Eastside. Worth the premium for homes where comfort and noise are priorities; not worth it strictly for fuel savings.
What a Furnace Installation Costs on the Eastside
Pricing varies significantly with efficiency tier, BTU capacity, and the scope of ancillary work required (gas line, venting, ductwork, electrical). The ranges below reflect typical Eastside residential conditions. Each quote is provided in writing as a flat rate after the site visit, never quoted blind over the phone.
| Configuration | Typical range |
|---|---|
| 80% AFUE single-stage furnace, like-for-like replacement | $5,500 – $7,500 |
| 95% AFUE condensing furnace, single-stage | $6,500 – $9,500 |
| 96% AFUE condensing furnace, two-stage | $8,500 – $11,500 |
| 97-98% AFUE modulating premium furnace | $10,500 – $14,500 |
Ranges assume a like-for-like replacement scenario with existing ductwork in usable condition. Furnace installations requiring significant ductwork modification, new gas line, new electrical service, or chimney lining work fall outside these ranges. Conversions from non-condensing to condensing (i.e., adding PVC venting and a condensate drain to a home that previously had B-vent only) typically add $800 to $1,800 to the project.
PSE Rebates and Federal Tax Credits
Gas furnace incentives are smaller than heat pump incentives, reflecting the policy direction of both state and federal energy programs. They are not zero, however, and we file all paperwork on your behalf as standard scope.
PSE rebates
PSE offers $200 to $500 in rebates for qualifying high-efficiency natural gas furnaces, with the higher rebate tier reserved for 95% AFUE and above. PSE also offers separate incentives for dual-fuel hybrid systems pairing a heat pump with a gas furnace, where the rebate is paid against the heat pump portion of the installation.
Federal IRA Section 25C tax credit
The Inflation Reduction Act Section 25C credit covers 30% of qualifying furnace installation cost up to $600 for furnaces meeting the highest efficiency tier defined by the Consortium for Energy Efficiency. Most 96% AFUE and above furnaces qualify. The credit is claimed on your federal tax return for the year of installation; we provide the AHRI certificate and manufacturer documentation required to substantiate the claim.
Installation Day — What to Expect
A standard furnace replacement follows a predictable schedule.
- Pre-arrival. Permit is filed, the unit is ordered, and the install date is confirmed. You receive a confirmation the day before with the arrival window.
- Arrival and protection. Crew arrives, lays floor protection from the entry point to the utility area, and verifies scope with you. Total: 20-30 minutes.
- Removal of existing furnace. Gas is shut off at the meter or shutoff valve. Electrical is disconnected. The old unit is removed, palletized, and staged for disposal.
- New furnace installation. The new unit is set, leveled, and connected to the existing plenum. Sheet metal transitions are fabricated as needed.
- Venting and condensate. PVC venting is run through the sidewall or roof per code, with the required slope and support spacing. Condensate drain is plumbed and trapped.
- Gas, electrical, and thermostat. Gas line is connected and pressure-tested. Electrical disconnect is verified and the service switch is wired. New thermostat is installed and configured.
- Startup and combustion testing. Furnace is energized and run through a full cycle. Combustion analysis verifies CO output, gas pressure, and flue temperature. Documentation printout is provided to you and attached to the unit for inspector reference.
- Cleanup and walkthrough. Floor protection removed, packaging hauled away, and walkthrough covers operation, filter changes, and maintenance schedule.
- Inspection. Inspector visits within 1 to 2 weeks at a separately scheduled appointment.
Brands We Install
We install furnaces from the major American manufacturers. All five lines below produce reliable equipment with strong parts availability and good warranty support. We do not have an exclusive dealer relationship that biases our recommendation — your installation gets the brand that best fits the home, your budget, and the configuration on the day of the quote.
- Carrier and Bryant. Same parent company. Carrier is the premium tier; Bryant is the value tier with substantially the same engineering. Excellent variable-speed and modulating options.
- Trane and American Standard. Also same parent company. Strong reputation for durability. Trane premium models include excellent two-stage and modulating options.
- Lennox. Particularly strong premium modulating product (SLP99V). Parts availability slightly more limited than Carrier or Trane on the Eastside.
- Goodman and Daikin. Daikin owns Goodman; Goodman remains a value tier. Strong choice for budget-constrained projects where reliability matters more than absolute peak efficiency.
Get a Free Furnace Quote
Call our 24/7 dispatch line at 425-900-3610 to schedule a free in-home heating evaluation, or send your project details through the contact form. We provide a side-by-side furnace versus heat pump comparison on every quote so you can make the decision with full information. Written flat-rate quote is provided within 48 hours of the site visit.