Tankless Water Heater Installation in Seattle-Tacoma
Gas and electric tankless water heaters, sized for your home, with the gas line, venting, electrical and permits handled by one team. Free install estimates.
Locally-owned since 1977 • Licensed, bonded and insured in Washington (WA Contractor Reg. #HOMECCA785BD) • WA Plumbing Contractor Lic. #HOMECCA751QG (residential) • BBB Accredited Business since 2002
Tankless water heater installation, answered
A tankless water heater heats water only when you open a tap. Installing one means matching the unit to how much hot water your home uses at once, then checking the gas line or electrical circuit, the venting and the permit. Home Comfort Alliance installs gas and electric tankless water heaters for homes across the Seattle-Tacoma area. Every install starts with a free estimate, because the right unit depends on your house.
| Install estimate | Free |
| Tankless flush | $429 |
| Tankless service (no flush) | $230 |
| Plumbing repair visit (dispatch fee) | $99 |
WA Plumbing Contractor Lic. #HOMECCA751QG (residential) and WA Electrical Contractor Lic. #HOMECCA782DC. Call (425) 645-0404 or book online.
Is a tankless water heater right for your home?
A good fit when
- Your home already has natural gas service
- Space is tight and you want the heater on a wall
- Your household uses hot water in long stretches, like back-to-back showers
- You plan to stay in the home and want a heater that takes up less room
Look at other options when
- The home is all electric and the panel is already full
- You want the lowest upfront cost
- A heat pump water heater and its utility rebates fit your home better
What tankless can and cannot do
A tankless heater does not run out the way a tank does, but it can only heat so much water at once. If too many fixtures run together, the water gets cooler. Most units also need a small minimum flow to turn on. Sizing the unit for your peak use is what keeps showers hot. Compare both in tank vs tankless for Seattle homes.
What a tankless installation involves
Gas or electric
| Gas tankless | Electric tankless | |
|---|---|---|
| What it needs | A gas line sized for the unit's high gas input | A large dedicated circuit; most units need 50 to 200 amps at 208 or 240 volts (U.S. Department of Energy) |
| Venting | An approved vent route and termination, using vent parts listed for the unit | No combustion vent |
| Typical fit | Homes with gas service and several fixtures in use at once | Smaller loads, condos, or homes without gas and with panel capacity |
| What we check | Meter, pipe length, other gas appliances, vent path | Panel capacity and circuit; an electrical panel upgrade if needed |
One team handles it all: our plumbers, our licensed electricians and our gas piping work for appliances such as water heaters, furnaces, ranges and generators.
Gas line sizing
Gas tankless units use much more gas at full fire than most tank heaters. A U.S. Department of Energy guide notes the line serving the unit often needs to be 3/4 inch. We size it from the meter, the pipe length and your other gas appliances, following the manufacturer and the code.
Condensing or non-condensing
| Condensing | Non-condensing | |
|---|---|---|
| Heat exchanger | Pulls extra heat from the exhaust | One heat exchanger, hotter exhaust |
| Drain | Needs a condensate drain line | No condensate drain |
| Vent | Vent materials set by the manufacturer | A vent made for hotter exhaust |
| Rebates | Cascade's rebate needs a unit rated 0.95 UEF or higher, so check the unit's UEF rating | |
Sizing for your house
- List the fixtures you use at the same time. A shower is about 2 gallons per minute and a kitchen sink about 1.5.
- Find the temperature rise: your set temperature (120°F covers most homes, per the Department of Energy) minus the coldest water coming into your house in winter. Your water utility can tell you that figure.
- Choose a unit rated for that flow at that rise.
Condos and townhomes
Check with your HOA first. Many buildings limit vent routes, and some do not allow new gas service. Electric units avoid venting but need enough electrical capacity. See our condo tankless planning guide.
Permits
In Seattle and unincorporated King County, plumbing and gas piping permits come from Public Health Seattle and King County. Other cities issue their own. We pull the permits for the work we do and schedule the inspection.
Flushing after the install
Follow the schedule in your unit's manual. The Department of Energy says the interval ranges from twice a year to once every three years, depending on the manufacturer and how you use it. We flush tankless units for $429. See tankless maintenance.
How much does tankless installation cost?
We do not publish install price ranges, because the gas line, venting and electrical work change from house to house. Your estimate is free, and it lists each part of the job. Our fixed prices for tankless service are a $429 flush and a $230 tankless service without a flush.
Why switching from a tank costs more than the heater
- A new or larger gas line
- A new vent route through a wall or roof
- A condensate drain for a condensing unit
- An outlet or dedicated circuit, and possibly a panel upgrade for an electric unit
- Wall mounting and repiping at a new location
- Permits and inspection
- Removing the old tank
More detail: tankless water heater costs.
Third-party benchmark, not our price: Angi lists a Seattle tankless install at $1,925 to $3,500 for natural gas and $550 to $2,900 for electric, with a $2,915 average (read November 2026).
Rebates and financing
| Program | Amount | Requirements |
|---|---|---|
| Cascade Natural Gas | $1,000 | Tankless water heater rated 0.95 UEF or higher, installed on or after March 15, 2026; Cascade residential customer; apply within 90 days (Cascade 2026 to 2027 rebate list, read November 2026) |
| Puget Sound Energy | No tankless rebate listed | PSE offers a heat pump water heater rebate instead (November 2026). See PSE rebates. |
We handle the rebate paperwork for you. The federal 25C tax credit ended for equipment placed in service after December 31, 2025. See all rebates.
Payment plans are available through Salal Credit Union and Synchrony, starting at $179/month*. See financing.
*Subject to credit approval.
Our tankless installation process
- Free estimate. We count the fixtures you use at once and look at the space.
- Utility check. Gas line, venting route, or panel capacity for an electric unit.
- Permit. We pull the permits for our work.
- Install. Mount, pipe and vent the unit, then gas and leak test and start it up.
- Walkthrough. Your flush schedule, how to read the display, and the rebate paperwork.
You can book by phone or online at any time. Our plumbers work Monday to Friday, 8 AM to 5 PM, with same-day service when possible.
A recent tankless job in Bothell
In October 2026 a Bothell homeowner asked us to fix the venting on a condensing tankless water heater. The intake and vent pipes running through the attic were not sloped back toward the unit, which a condensing heater needs so its condensate drains the right way, and the condensate had no proper drain.
Our plumber cut out about 8 inches of each riser in the attic and regraded both pipes back toward the tankless, then ran the condensate drain, and the relief valve drain, to the laundry sink in the garage. The unit worked with no leaks. Vent slope and a condensate drain are two of the details we plan on every tankless install.
Where we install tankless water heaters
We install tankless water heaters in homes across the Seattle-Tacoma area, from our Redmond, Everett and Bremerton branches and our Sumner headquarters. Local pages: tankless installation in Tacoma, tankless installation in Bremerton and water heater replacement in Seattle. See all service areas.
Tankless water heater installation FAQ
Why does switching from a tank to tankless cost more than the heater?
A tank and a tankless heater need different things from your house. A gas tankless unit often needs a larger gas line, a new vent route and a condensate drain. An electric unit may need a large dedicated circuit or a panel upgrade. Permits, mounting and removing the old tank add to the job. We list each item on your free estimate.
How often should a tankless water heater be flushed?
Follow the schedule in your unit's manual. The U.S. Department of Energy says the interval ranges from twice a year to once every three years, depending on the manufacturer and how you use it. Our tankless flush is $429. A tankless service without a flush is $230.
My tankless water heater shows an error code. What should I do?
Write down the code and the model number from the label on the unit. Codes differ by manufacturer, so check the manual first. If the code comes back, call us at (425) 645-0404 and tell us the code when you book. The plumbing dispatch fee is $99.
Can I replace my 40 or 50 gallon tank with a tankless water heater?
Yes, in most homes. The tankless unit is sized by how much hot water you use at the same time, not by gallons stored. We check the gas line or electrical circuit, the venting and the space before we recommend a unit.
Gas or electric tankless: which is better?
Gas units usually serve more fixtures at once and need venting and the right size gas line. Electric units need no vent, but most need 50 to 200 amps, according to the U.S. Department of Energy. If your home has no gas, we check your panel first.
Will I need a bigger gas line?
Often, yes. Gas tankless units use far more gas at full fire than most tank heaters. A Department of Energy guide says the line serving the unit often needs to be 3/4 inch. We size the line from your meter, the pipe length and your other gas appliances. Gas line installation is one of our services.
What size tankless water heater do I need?
Add up the flow of the fixtures you use at the same time. A shower is about 2 gallons per minute. Then find the temperature rise: your set temperature minus the coldest water coming into your house. The unit must deliver that flow at that rise in winter.
Do I need a permit to install a tankless water heater in Seattle?
In Seattle and unincorporated King County, plumbing and gas piping permits come from Public Health Seattle and King County. Other cities issue their own. We pull the permits for the work we do and schedule the inspection.
Are there rebates for tankless water heaters?
Cascade Natural Gas offers $1,000 for a tankless water heater rated 0.95 UEF or higher, for installs on or after March 15, 2026. You must be a Cascade residential customer, and the application is due within 90 days. Puget Sound Energy does not list a tankless rebate as of November 2026.
Does a tankless water heater give endless hot water?
It does not run out like a tank, but it can only heat so much water at once. If too many fixtures run together, the water gets cooler. Sizing the unit for your peak use is what keeps showers hot.
Can I install a tankless water heater in a condo?
Often, but check with your HOA first. Many buildings limit vent routes, and some do not allow new gas service. Electric units avoid venting but need enough electrical capacity. Our condo planning guide covers the questions to ask.
What is the difference between condensing and non-condensing tankless heaters?
A condensing unit pulls extra heat from its exhaust, so it is more efficient. It makes acidic water that needs a drain line. A non-condensing unit has hotter exhaust and needs a vent made for it. Rebates like Cascade's require a high efficiency rating, so check the unit's UEF.
Why Choose Home Comfort Alliance for Tankless Installation?
Your Comfort is Our Promise
Reliable heating, air conditioning, plumbing and electrical service, all from one trusted company.
To educate and guide you through your options so you’ll find the right solution at the right price.
Knowledgeable and respectful workers who ensure both your own comfort during every visit, and lasting comfort from your home systems.
Outstanding service, communication, and follow-up, so your home is comfortable now and for years to come.
Get a free tankless estimate
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