Tankless water heater installation cost in Seattle

Tankless water heater installation cost — FAQ

How much does it cost to install a tankless water heater?

A tankless water heater typically runs $1,100–$5,500 installed, averaging around $3,000. Gas units cost more ($2,100–$5,600) because of venting and gas-line work; electric on-demand units are cheaper ($1,400–$3,000) but may need an electrical upgrade.

Gas vs. electric tankless — which costs more?

Gas tankless units cost more to buy and install (venting and gas-line work), but often cost less to run and suit whole-home demand. Electric tankless units are cheaper to install but can need a significant electrical upgrade for whole-home use.

Is a tankless water heater worth it versus a tank?

Tankless units cost more upfront than a standard tank ($1,200–$2,500) but last longer (often 20+ years), save space, and only heat water on demand. The energy savings are real but modest for most homes; endless hot water and longevity are the bigger draws.

Why is switching from a tank to tankless more expensive?

A first-time conversion usually needs new venting, a larger gas line, or upgraded electrical to support the on-demand unit — work you don't need when simply swapping one tankless for another.

What's the practical difference between gas and electric tankless installs?

A gas unit needs dedicated venting run to the outside, and sometimes a bigger gas line to feed it. An electric unit skips the venting but needs enough spare capacity in your panel — a whole-home electric model typically wants its own high-amperage circuit, which older panels sometimes can't support without an upgrade. In colder climates, gas tends to keep up with whole-house demand more comfortably, since it isn't capped by the same electrical-capacity ceiling.

What does venting a gas tankless water heater involve?

Condensing (high-efficiency) units vent through PVC pipe, which is cheaper to install and easier to route through a wall. Standard non-condensing units need stainless-steel venting, which costs more and is pickier about run length and clearance from windows and doors. If you're converting from a tank, a plumber will check this early, since it can decide whether the new unit can even go where the old one sat.

What size tankless water heater does my household need?

Sizing comes down to two things: how many fixtures might draw hot water at once (a shower running while the dishwasher goes, say) and how cold your incoming water runs in winter, since colder groundwater means the unit works harder to reach the same output temperature. A point-of-use unit under one sink is a different job from a whole-home unit meant to cover several bathrooms, and an undersized whole-home unit is a common source of tankless complaints — not a flaw in the technology itself.

Do I need a permit to install a tankless water heater?

In most jurisdictions, yes — the work touches plumbing and either gas or electrical wiring, and both typically require a permit and inspection. Skipping it can come back to bite you later: unpermitted work has a way of surfacing during a home sale or an insurance claim. A licensed installer usually pulls the permit as part of the job, so if a bid doesn't mention one, ask directly.

How do I compare tankless water heater installation quotes?

Ask each contractor to break out the unit, labor, and any venting, gas-line, or electrical work as separate line items — a single lump sum hides which part of the job is driving the price. Check that the brand, flow capacity, and efficiency tier actually match across bids, since a lower number sometimes just means a smaller unit. If you already have a quote in hand, run it through our quote checker to see where it lands against our published range and what could explain a higher figure.