Quick answer
In Puget Sound, groundwater arrives cold — roughly 45–50°F much of the year — and cold inlet water is the tankless stress test. A condensing gas unit fires around 199,000 BTU and holds multi-fixture flow through that lift; a whole-home electric unit needs on the order of 100–150 amps to attempt the same, which most panels can't spare. Gas is the standard whole-home answer here; electric tankless shines at point-of-use.
- Tankless output is a flow-rate-at-temperature-rise problem: the colder the inlet, the fewer simultaneous fixtures any unit can hold. Our inlet water is cold most of the year.
- Whole-home electric tankless draws are enormous — commonly 100–150 amps of dedicated capacity — which collides with the same 200A panel budget your heat pump, range, dryer, and EV charger are negotiating over.
- A condensing gas tankless (the Navien class we install) vents in PVC, modulates to demand, and routinely needs a gas line upsized to feed its ~199k BTU fire rate — that's part of a real quote.
- Point-of-use electric tankless is the honest electric win: a small unit at a far bathroom or shop sink, no whole-home pretensions, no panel drama.
- No 2026 rebate favors either: Washington's water-heater incentives point at heat pump water heaters, not tankless of any fuel.
At a glance
| Gas tankless (condensing) | Electric tankless (whole-home) | |
|---|---|---|
| Cold-climate flow | Multi-fixture at 45–50°F inlet | Struggles at our temperature rise — flow drops fast |
| Infrastructure ask | Gas line sizing + PVC venting + condensate | 100–150A of panel capacity most homes don't have |
| Right role | Whole-home on-demand hot water | Point-of-use boosts; small whole-home only in mild-load homes |
| Electrification fit | Keeps a gas appliance in the house | Electric — but the HPWH is the electric option rebates fund |
| 2026 rebates | None | None (heat pump water heaters carry the incentives) |
What does each option cost installed in the Seattle area?
Whole-home tankless pricing below matches our published water-heater cost canon. Electric point-of-use units are a different, much smaller product — priced per install, not per canon range.
| Option | Typical installed range | What that covers |
|---|---|---|
| Gas tankless, installed | $6,500–$10,000 | Condensing unit with venting, condensate handling, gas-line sizing/upsizing as needed, permit, and code items — the whole-home standard. |
| Whole-home electric tankless | Quoted per home — panel capacity decides | Hardware is cheaper than gas; the dedicated 100–150A of circuits (and often a service upgrade at $8,000–$16,000) is where the real number lives. |
| Point-of-use electric tankless | Quoted per install | A small unit and one circuit at the fixture that's far from the main heater. |
What changes the price
- Panel headroom: run the load calculation before falling for electric tankless hardware prices — the service upgrade is the hidden line item.
- Gas line sizing: a 199k BTU appliance often needs a larger gas run than the old tank used; we size it as part of the quote.
- Venting path: condensing units vent in PVC with a condensate drain — routing is usually easy, but it's a real scope item.
- Simultaneous demand: household fixture habits size the unit; PNW inlet temps mean sizing conservatively.
Ranges are representative Seattle / Puget Sound installed prices, not a quote — your home's specifics set the real number. Eco gives you an upfront price before any work begins.
How do they work differently?
How gas tankless handles our cold water
A condensing gas burner modulates up to roughly 199,000 BTU on demand — enough energy to lift 45°F water to shower temperature across multiple simultaneous fixtures, with efficiency in the mid-to-high 90s because a second heat exchanger scavenges the exhaust. The machine's appetite is the install's constraint: the gas line must feed that fire rate, and the venting must carry its cool, acidic exhaust in plastic pipe to the outdoors.
Why electric tankless struggles at whole-home scale here
Electric resistance can absolutely make hot water instantly — the question is amperage. Lifting our cold inlet water at a real multi-fixture flow takes on the order of 25–36 kW, which is 100–150 amps of dedicated capacity at 240V. On a typical 200A service that's most of the panel for one appliance, on wire sized like a small subfeed. At point-of-use scale — one sink, one shower boost — the same technology is modest, cheap, and genuinely useful.
Pros and cons, honestly
Gas tankless
Pros
- Holds multi-fixture flow through PNW temperature rise
- Endless hot water with condensing-class efficiency
- Compact wall-mount frees floor space
- Mature whole-home product category (Navien-class units we install daily)
Cons
- Keeps a gas appliance (and meter) in an otherwise electrifying home
- Gas-line upsizing and venting are real scope items
- No rebate support in 2026
Electric tankless
Pros
- No venting, no gas line, no combustion
- Excellent at point-of-use — remote bathrooms, shops, ADU sinks
- Small physical footprint, simple hardware
Cons
- Whole-home draw of 100–150A collides with panel reality
- Flow drops hard at our cold inlet temperatures
- Often triggers a service upgrade that dwarfs the unit cost
- The electric water heater rebates fund is the HPWH, not this
Which one should you choose?
Choose gas tankless when
You want whole-home endless hot water, gas service already exists, and the mechanical room can host venting and condensate. It's the configuration this product category was built for, and at our inlet temperatures it's the one that actually delivers simultaneous showers in January. Size it to your real fixture habits — that's a conversation, not a catalog lookup.
Choose electric tankless when
The job is point-of-use: the primary bath at the far end of the house, the shop sink, the ADU kitchenette — places where a small unit on one honest circuit beats running hot water lines across the building. For whole-home electric hot water, run the numbers on a heat pump water heater first: it's the electric option that wins on operating cost and carries every 2026 incentive.
Also consider: the heat pump water heater
If the appeal of electric tankless is 'electric,' the heat pump water heater is the stronger version of that argument: a fraction of the operating cost of resistance, WA HEAR point-of-sale support up to $1,750 for income-eligible households plus utility rebates, and no triple-digit amperage demands. It trades 'endless' for 'extremely cheap and rebated' — for many homes, the better trade.
The verdict, by situation
Gas tankless
The whole-home standard here
The only tankless configuration that comfortably serves a full Puget Sound household through winter inlet temperatures.
Electric tankless
A point-of-use specialist
Brilliant at one fixture; a panel-budget crisis at whole-home scale. Buy it for the job it's good at.
HPWH
The electric whole-home answer
If the goal is electric hot water, this is the version Washington's rebates — and the operating-cost math — actually endorse.
Which Washington homes this fits
Gas-served family home, four back-to-back showers
Condensing gas tankless, sized honestly — this is its home turf, endless hot water through the winter inlet chill.
Electrifying home planning heat pump + EV charger
Don't spend 100+ amps on hot water. HPWH for the house; a point-of-use electric unit if one far fixture needs help.
ADU or DADU with a kitchenette and one bath
Small loads change the math — a compact electric unit or small HPWH can serve without gas plumbing at all.
Shop, studio, or far-flung utility sink
Point-of-use electric tankless: one circuit, instant hot water, no 60-foot dead leg of cold pipe to run out.
Ready to compare for your home?
Get honest numbers for both options side by side — an upfront range, the considerations, and the rebates you qualify for, before any work begins.
Continue exploring
- BookTankless water heaters
- BookWater heater services
- BookGas line services
- CompareCondensing vs Standard Tankless: Which Water Heater Should You Buy?
- CompareTankless vs Heat Pump Water Heater: Endless vs Cheapest
- CompareGas vs Electric Water Heater: Which Fuel Should a Washington Home Pick?
- GuideTankless vs tank — the full evaluation
- GuideWater heater cost guide
- GuideWater heater installation code guide
- CompareAll plumbing & water comparisons
Common questions
Why does inlet temperature matter so much for tankless?
Because a tankless unit heats water in real time, its flow rate is set by how far it must lift the temperature. Warm-climate spec sheets assume 60–70°F inlet water; Puget Sound water arrives around 45–50°F much of the year. The same unit that serves three fixtures in Phoenix serves fewer here — which is why we size against winter inlet, not the brochure.
Can my panel run a whole-home electric tankless?
Usually not without major work. Whole-home units commonly want 100–150 amps of dedicated capacity — most of a 200A service for one appliance. We run the NEC load calculation, and in most cases the honest advice is a gas tankless or a heat pump water heater instead of a service upgrade bought for resistance hot water.
Do tankless water heaters get rebates in Washington in 2026?
No — neither fuel. The federal 25C credit expired December 31, 2025, and Washington's live water-heater incentives (WA HEAR up to $1,750 point-of-sale for income-eligible households, plus utility programs) apply to heat pump water heaters only.
Will my existing gas line feed a tankless unit?
Often it needs upsizing. A tankless fires at up to ~199,000 BTU — several times a tank's burner — and the line that fed the old tank may be too small for that draw, especially on longer runs. Gas-line evaluation and sizing is part of our tankless quote, not a surprise afterward.
Last updated: 2026-07-17
Sources & references
Equipment ratings, program details, and industry figures on this page come from manufacturers and primary sources, linked below. Verify program status and requirements for your home where applicable.
Equipment
- Tankless water heater efficiency and performance categories — ENERGY STAR — Water Heaters
- Condensing gas tankless product specifications (fire rates, venting) — Navien (Eco is a Navien-authorized installer)
Electrical & rebates
- Electrical circuit and service changes require permits and inspection in Washington — WA L&I — Electrical permits, fees & inspections
- Washington's water-heater incentives fund heat pump water heaters — WA Commerce — HEAR program