What each option is
A heat pump uses the refrigeration cycle to move heat: it cools the house in summer and reverses operation to heat in winter. A gas furnace burns fuel gas, transfers heat through a heat exchanger, and pushes warm air through the duct system. In Washington, both choices need sizing and duct review before price becomes meaningful. ACCA Manual J is the load calculation reference, ACCA Manual S is the equipment-selection reference, and ACCA Manual D is the duct-design reference. Gas furnaces add combustion-air, venting, gas shutoff, drip-leg, and gas-load issues under the fuel-gas code, including IFGC Chapter 3 and Chapter 4 concepts. Heat pumps add refrigerant, defrost, backup heat, condensate, electrical disconnect, and balance-point decisions.
State-specific factors
The state-content seed makes this a Washington comparison, not a generic national one. It lists Seattle, Vancouver, Bellevue as the deepest directory metros, identifies Washington Department of Labor & Industries (L&I) and the local authority having jurisdiction (https://lni.wa.gov/licensing-permits/contractors/) for the hvac licensing path, and summarizes licensing this way: Washington requires all construction contractors to register with the Department of Labor & Industries (L&I) as a General or Specialty contractor. Electricians and plumbers are licensed by L&I trade boards. It also gives the HVAC installation cost band as $5.5K-$18.5K with $10.5K typical. The companion buyer-guide context uses the same state-trade source data to ask who pulls the permit, which credential applies, what insurance proof is required, and what inspections close the job. Standards references are included to frame scope, but the adopted local edition still controls. Where the seed does not publish utility tariffs or local amendments, this guide names that gap rather than filling it with guesses. Use the written bid to connect every cost assumption back to those source facts. Ask bidders to attach model numbers, permit responsibility, warranty labor, and excluded repair work to the same line-item scope. The climate planning lens is marine west-side weather, colder eastern counties, seismic concerns, and electric-heavy housing make load and moisture assumptions local. For HVAC, climate and utility prices change the operating answer more than the equipment label. ACCA Manual J load calculation, Manual S equipment selection, Manual D duct review, and IFGC combustion-air rules are the standards that keep bids comparable. Heat pumps gain value where cooling, shoulder-season heating, and electrification matter; gas furnaces gain value where gas service already exists and deep-cold output is the priority. The seed does not publish local fuel rates, so the contractor should state the electric and gas assumptions used for the comparison.
Cost comparison
Heat Pump
$10.5K-$18.5K
Uses the typical-to-high HVAC band when the project adds outdoor equipment, electrical work, backup heat, controls, or duct corrections.
Gas Furnace
$5.5K-$10.5K
Uses the low-to-typical band when gas service, venting, ducts, and thermostat wiring are already suitable.
Source band: HVAC installation: $5.5K-$18.5K (typical $10.5K)
The state-content costBand for Washington lists HVAC installation at $5.5K-$18.5K with $10.5K typical. A gas furnace replacement tends to use the low-to-typical part when the gas line, vent, return air, supply ducts, condensate, and thermostat wiring already work. A heat pump or dual-fuel conversion tends to use the typical-to-high part when it adds outdoor equipment, line-set changes, electrical work, backup heat, controls, duct corrections, or load-balancing. The low-to-typical spread is $5K; the typical-to-high spread is $8K. The delta narrows when the air conditioner was due for replacement anyway and widens when the electrical service or ducts are not ready.
Permit / inspection differences
Use the Washington licensing primer first: Washington requires all construction contractors to register with the Department of Labor & Industries (L&I) as a General or Specialty contractor. Electricians and plumbers are licensed by L&I trade boards. The trade entry points to Washington Department of Labor & Industries (L&I) and the local authority having jurisdiction (https://lni.wa.gov/licensing-permits/contractors/), with ProFix license slug hvac-license-in-wa. Local permit offices still decide the exact permit type, adopted code edition, and inspection sequence. A heat pump install usually needs mechanical/HVAC inspection and may add electrical disconnect, refrigerant-line, condensate, duct, and backup-heat checks. A gas furnace usually needs mechanical plus fuel-gas or combustion inspection for venting, gas connector, drip leg, combustion air, condensate on condensing units, and startup documentation. Either option should close with permit status, model numbers, commissioning notes, and warranty paperwork before final payment.
Verdict by scenario
Verdict Washington: heat pump Washington versus gas furnace Washington. Choose heat pump Washington when Washington cooling matters, Washington shoulder-season heat matters, Washington ducts are verified, Washington electrical capacity is documented, and Washington utility assumptions support electrification. Choose gas furnace Washington when Washington gas service is sound, Washington venting is sound, Washington envelope repairs are deferred, and Washington cold-weather risk should stay low. Compare Washington Manual J/S math, Washington airflow, Washington backup heat, Washington condensate routing, and Washington commissioning notes before signing.