The vocabulary you'll meet in quotes, spec sheets, and rebate forms — defined the way we'd explain them at your kitchen table, with the Seattle-specific context that actually matters.
The percentage of a furnace's fuel that becomes usable heat over a year. A 95% AFUE furnace turns 95 cents of every fuel dollar into heat; the rest leaves through the vent. Modern high-efficiency (condensing) furnaces run 90–98% AFUE, while many older units run 80% or below.
Seattle note: With Seattle-length heating seasons, the fuel savings from a higher-AFUE furnace add up faster than in milder climates.
The indoor unit that moves conditioned air through your ducts — blower, coil, and filter housing in one cabinet. In a heat pump system, the air handler is the indoor half; it contains no burner.
Seattle note: Heat-pump air handlers in Seattle often include electric strip backup — configured correctly, strips run rarely; misconfigured, they erase the savings the heat pump was bought to deliver.
The outdoor temperature at which a heat pump's output exactly matches your home's heat loss. Below the balance point, supplemental heat (electric strips or a furnace in dual-fuel setups) makes up the difference. Modern cold-climate heat pumps push the balance point low enough that supplemental heat rarely runs in Western Washington.
Seattle note: Seattle's mild winter lows are comfortably inside a modern heat pump's efficient range — the main reason heat pumps pencil out so well here.
The basic unit of heating and cooling energy — the heat needed to raise one pound of water by 1°F. Equipment capacity is stated in BTU/h (BTUs per hour); 12,000 BTU/h equals one ton of cooling.
Seattle note: Seattle's mild design temperatures mean heat pumps are often sized smaller than intuition suggests — oversizing in BTUs causes short-cycling, the comfort killer in our climate.
A small electrical component that gives AC and heat pump motors their starting kick and smooths their running power. It's the part most murdered by heat waves — and the classic symptom is an outdoor unit humming or clicking while its fan stands still.
Seattle note: Capacitors weaken measurably before they die, which is why the spring tune-up's capacitor reading prevents so many first-heat-wave failures in Seattle's repair queues.
AC blowing warm? The suspects in order What a real tune-up includes
A heat pump engineered to keep heating efficiently in sub-freezing weather, using variable-speed compressors and enhanced refrigerant circuits. Certified cold-climate models maintain useful capacity well below the temperatures a standard heat pump handles.
Seattle note: Utility rebates in the Seattle area key off efficiency tiers (see HSPF2) — higher-tier cold-climate equipment earns bigger discounts. PSE's ductless gas-conversion path requires ≥9.5 HSPF2, which cold-climate lines routinely exceed.
The pump at the heart of an AC or heat pump that pressurizes refrigerant so it can move heat. Single-stage compressors are on/off; two-stage and variable-speed compressors modulate output for steadier temperatures, better humidity control, and lower bills.
Seattle note: Inverter compressors in ductless heads are why Seattle homeowners notice the difference immediately — whisper-quiet operation and no temperature sawtooth on mild 40–50°F heating days.
The small line that carries away the water your system produces — condensation from the AC coil in summer, and (on high-efficiency furnaces) acidic condensate from combustion year-round. Clogged condensate paths are the quiet cause of summer water stains and shutdowns.
The outdoor half of an AC or heat pump, where refrigerant releases (or in heating mode, absorbs) heat. It houses the compressor, outdoor coil, and fan. Keeping it clear of leaves and shrubs protects airflow and efficiency.
Seattle note: Seattle's tree canopy and wet climate mean condenser coils clog faster than drier regions — annual coil cleaning is standard maintenance-plan scope on Elite, and worth doing before every cooling season regardless.
A high-efficiency gas furnace (90%+ AFUE) that captures extra heat by condensing water vapor out of its exhaust. It vents through PVC pipe instead of a metal flue and needs a condensate drain — two install details that affect replacement cost.
Seattle note: Most furnace replacements in the Seattle area are now condensing units — WA energy code and the economics of 90%+ AFUE make 80% non-condensing swaps increasingly rare except on tight-budget projects.
A heat pump's routine for melting frost off its outdoor coil: the system briefly reverses into cooling mode, sending hot refrigerant outside until the coil clears. Steam, a whoosh at changeover, and a few minutes of cooler indoor air are all normal defrost behavior.
Seattle note: Puget Sound's damp 30s-and-40s winters are prime frost weather — local heat pumps defrost often, and that's the design working, not failing.
A heat pump paired with a gas furnace. The heat pump handles most of the season efficiently; the furnace takes over on the coldest days. A smart control decides the switchover point automatically.
Seattle note: PSE offers a hybrid heat pump rebate for pairing a heat pump with your existing gas furnace — see the rebate stack on our heat pump cost guide.
Closing the leaks in supply and return ductwork so conditioned air reaches rooms instead of the crawlspace. Leaky ducts can waste a large share of the heating and cooling you pay for, and duct condition is a standard checkpoint before any equipment upgrade.
Seattle note: WA code brings duct testing into HVAC replacements — ~15% leakage is the action threshold. Sealing before a heat pump install reclaims capacity the old furnace never delivered.
A heat pump that skips ductwork entirely: one outdoor unit feeds one or more wall- or ceiling-mounted indoor heads, each heating and cooling its own zone. Ideal for homes without ducts, additions, ADUs, and rooms the ductwork never reached.
Seattle note: A large share of Seattle's older housing stock was built without central ducting — ductless avoids $5,000–$15,000 of duct retrofit work.
Your home's circuit-breaker box and the amperage of its main service — the hidden line item in heat pump retrofits. The main breaker's number (60, 100, 125, 200) is your service size; a heat pump needs a dedicated 240-volt circuit with real headroom.
Seattle note: Pre-war Seattle homes commonly carry 60–100 amp service. Sometimes capacity exists; sometimes a panel upgrade joins the electrification project — regional guidance often lands full electrification at 150–200 amps.
Balanced ventilation systems that exhaust stale indoor air and bring in fresh outdoor air continuously — while transferring most of the heat (HRV) or heat and moisture (ERV) between the two streams. They solve the tight-house stuffiness problem without throwing away the energy you paid for.
Seattle note: In the Puget Sound climate, HRVs are the common choice — our winters are damp enough that recovering humidity (the ERV's specialty) is rarely the goal.
The indoor coil where refrigerant absorbs heat from your home's air in cooling mode. It sits above the furnace or inside the air handler. A frozen or dirty evaporator coil is one of the most common causes of weak cooling.
Seattle note: In heating mode on a heat pump, this same coil reverses roles — it's where heat is delivered to your home's air. Keeping it clean matters year-round in Seattle's year-round heat pump duty cycle.
The sealed metal passage inside a gas furnace that transfers combustion heat to your home's air while keeping exhaust gases separate. A cracked heat exchanger can leak carbon monoxide and usually means the furnace is at end of life — it's the classic replace-don't-repair failure.
Seattle note: Heat exchanger inspections are standard scope on every Glendale tune-up — cracks are the safety finding that turns a repair call into a replacement conversation, especially on furnaces past 15 years.
An all-electric system that moves heat rather than making it — extracting warmth from outdoor air in winter and reversing to cool in summer. One machine replaces both furnace and AC, and because moving heat beats generating it, efficiency is far higher than electric-resistance heating.
Seattle note: Washington's mild winters are ideal heat-pump territory, and active Seattle City Light / PSE rebates take $1,500–$6,000 off qualifying conversions.
Electric resistance coils inside an air handler that back up a heat pump — simple and reliable, but they heat at one-half to one-quarter of the heat pump's efficiency. Well-designed Seattle systems use them rarely; strips running constantly signal a sizing or configuration problem.
Seattle note: The classic 'my new heat pump didn't lower my bill' story here is usually strips engaging on every recovery from a deep nighttime setback — a settings fix, not an equipment failure.
High-Efficiency Particulate Air filtration — captures at least 99.97% of particles at 0.3 microns, the hardest size to catch. Whole-home HEPA systems mount to your ductwork and clean the air in every room, not just one.
Seattle note: During Seattle's late-summer wildfire smoke season, HEPA-grade filtration is what actually clears fine smoke particulate indoors.
The current federal test metric for heat pump heating efficiency — total seasonal heat output divided by electricity used, under a tougher 2023 test procedure than the old HSPF. Higher is better; cold-climate models carry the top ratings.
Seattle note: Seattle City Light's instant heat-pump discounts step up through HSPF2 tiers (8.1 / 8.5 / 9.5) — the rating directly changes your rebate.
A compressor that varies its speed continuously instead of switching between off and full blast — sprinting to temperature, then gliding at a whisper to hold it. It's why modern ductless heads run in the low-20s dB range and why room temperatures stay steady instead of sawtoothing.
Seattle note: Seattle's hundreds of mild heating days are exactly where inverter equipment shines — long, gentle, efficient cycles instead of constant hard starts.
The insulated copper refrigerant lines (plus control wiring and a condensate drain) connecting an outdoor unit to its indoor unit or heads. On ductless installs the bundle needs only a three-inch wall opening — the reason mini-splits retrofit so cleanly into finished homes.
The engineering math that determines how much heating and cooling your specific home needs, from measurements, insulation, windows, air-sealing, and orientation. See Manual J — the industry-standard method. Skipping it is how systems end up over- or undersized.
Seattle note: In Seattle's mild climate, load calculations often produce smaller equipment than homeowners expect — right-sizing is the single biggest comfort and efficiency lever on any install.
The ACCA industry-standard load-calculation procedure for sizing residential HVAC equipment. A real Manual J uses your home's actual measurements and construction details — not square footage alone — to pick capacity. An oversized or undersized system costs comfort and money for its entire 15–20 year life.
Seattle note: Glendale runs load calculations on every install — Seattle's varied housing stock (pre-war to 2000s suburban) makes square-footage guessing especially unreliable here.
Minimum Efficiency Reporting Value — a 1–20 scale for how well a filter captures particles. Household filters typically run MERV 8–13; higher ratings catch finer particles (smoke, allergens) but restrict airflow more, so the right rating depends on your blower and ductwork.
Seattle note: For wildfire smoke season, many Seattle systems can step up to MERV 13 — but airflow should be verified first. We check before recommending.
The sheet-metal box where your ductwork meets the equipment: the supply plenum distributes conditioned air out to the duct runs; the return plenum collects air coming back. The AC or heat pump's indoor coil typically lives in the supply plenum above a furnace.
Seattle note: Custom plenums and transitions are exactly what Glendale's in-house sheet metal shop fabricates — the odd geometries of older Seattle basements rarely fit catalog parts.
One of the new lower-global-warming refrigerants that replaced R-410A in new residential equipment as of 2025's federal transition. It's classified A2L ('mildly flammable'), which drove new handling standards, sensors, and equipment designs — and it's what new systems we install largely run on.
Seattle note: For owners of R-410A systems: nothing changes today — service continues for years. The practical effect is on repair-vs-replace math as R-410A service parts and refrigerant gradually cost more.
The working fluid that carries heat between the indoor and outdoor coils of an AC or heat pump. Modern systems use lower-global-warming refrigerants (the industry moved to A2L blends like R-454B and R-32 in 2025); older R-410A and R-22 systems face rising service costs as supplies tighten.
Seattle note: New equipment installed in 2025 and beyond runs on A2L refrigerants (R-454B, R-32). Existing R-410A systems continue to be serviceable — but repair-vs-replace math shifts as R-410A costs climb over the next decade.
The amount of refrigerant in a system — set precisely at install and unchanged for life unless there's a leak. 'It just needs a recharge' every summer means a leak diagnosis is being deferred annually at full price: systems don't consume refrigerant.
How much moisture the air holds compared to what it could hold at its temperature, as a percentage. The healthy indoor target is 30–50%: above ~55% sustained invites condensation, dust mites, and mold on cool surfaces; below 30% (rare here) brings static and dry skin.
Seattle note: Puget Sound's issue is winter damp — months of moist air meeting cool surfaces in older housing. Two $15 hygrometers beat guessing about it.
The current federal test metric for AC and heat pump cooling efficiency — seasonal cooling output divided by electricity used, measured under the stricter 2023 test procedure. Higher SEER2 costs more up front and less every summer.
Seattle note: Seattle's historically mild summers mean SEER2 tier matters less than HSPF2 for total annual savings — but warming summers and more AC adoption are changing that calculus.
When a system starts and stops in rapid bursts instead of running steady cycles. Causes range from an oversized unit to a clogged filter or failing sensor. It wears parts fast and wrecks efficiency — worth a diagnostic visit, not a wait-and-see.
Seattle note: Short cycling is the most common comfort complaint on oversized systems in Seattle's mild climate — where equipment sized for a colder region never gets a long heating or cooling run.
A connected thermostat that learns schedules, senses occupancy, and optimizes run times — trimming energy use without comfort loss. Correct configuration matters most with heat pumps, where a wrong setting can force expensive supplemental heat.
Seattle note: PSE offers a $75 rebate ($175 income-qualified) on ENERGY STAR smart thermostats with occupancy sensing.
The resistance your blower pushes against to move air through ducts, filter, and coil — HVAC's version of blood pressure. High static pressure (undersized ducts, restrictive filters) strains motors and starves rooms of airflow. It's measured, not guessed, during a proper system evaluation.
Seattle note: Static pressure readings are standard scope on Glendale tune-ups — they're how we determine whether your system can handle a MERV 13 upgrade or needs a media cabinet instead.
A unit of cooling capacity equal to 12,000 BTU/h — roughly the melt rate of a ton of ice per day. Residential systems typically run 1.5–5 tons. The right tonnage comes from a Manual J load calculation, not from matching whatever size was there before.
Seattle note: Seattle's mild summer design temperatures often produce 2–3 ton recommendations for typical homes — smaller than Sun Belt sizing and another reason right-sizing matters here.
Equipment that can run at partial output instead of full-blast on/off. Two-stage units have a low and high setting; variable-speed (modulating) equipment adjusts continuously. The payoff is steadier temperatures, quieter operation, better humidity control, and lower bills.
Seattle note: Seattle's hundreds of mild heating days (40–50°F) are where two-stage furnaces and inverter heat pumps earn their premium — long low-fire cruising instead of constant on/off.
Ultraviolet lamps mounted inside ductwork or at the coil that neutralize mold, bacteria, and viruses as air passes. They work alongside filtration — the filter catches particles; UV addresses the biological growth filters can't.
Seattle note: Coil-mounted UV is especially useful in Seattle's damp climate — evaporator coils stay wet during heating season, and UV prevents the mold growth that thrives on a dark, moist surface.
Dividing a home into independently controlled temperature areas, via motorized duct dampers or multiple ductless heads. Zoning fixes the classic too-hot-upstairs problem and stops paying to condition empty rooms.
Seattle note: Two-story suburban homes in the Seattle area are the #1 zoning use case — upstairs/downstairs dampers with separate thermostats fix stratification without oversizing the furnace.
Call us and a real person will translate it — and if you have a replacement quote in hand, our second opinion is free.
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