Tankless Water Heater Cost, Installed

1. What a Tankless Water Heater Costs, Installed

Start with the installed number, because it is the only one that matters. A tankless heater replacing a gas tank in an average house costs $3,000 to $6,500 all in. An electric whole-house unit costs $1,500 to $3,500 if your panel can carry it and $3,500 to $7,000 or more if it cannot. A small point-of-use heater under a sink is the cheap end of the category at $300 to $1,200 installed.

Those ranges are wide because the same heater can need almost nothing or almost everything around it. A condensing gas unit going into a basement with a 3/4-inch gas line already in place, a sidewall a few feet away and a floor drain next to it is a one-day job for a plumber. The identical unit going into a house with a 1/2-inch line, a shared chimney and no drain nearby can double the bill before the heater is even hung on the wall.

Compare that with what you would otherwise spend. A like-for-like 40 or 50 gallon gas tank typically installs for roughly $1,500 to $3,000, and an electric tank for a little less. So the honest framing is not what tankless costs but what it costs extra: usually $1,500 to $3,500 more than replacing the tank you have, sometimes more. Everything else in this guide is about where that premium comes from and whether you get it back.

One rule holds across every quote we have seen: compare installed prices, never unit prices. The models in our tested tankless water heater rankings differ by a few hundred dollars on the shelf, while the installation differences between a good and a bad fit for your house run into the thousands.

2. Unit Cost by Type

Electric point-of-use units cost $150 to $500. These are small heaters, typically 3 to 13 kW, that serve one sink or one shower from a cabinet or wall. They are the cheapest way to fix a single slow fixture far from the main heater, and they are not whole-house equipment. The smallest 120-volt models only manage a hand-washing flow; anything that feeds a shower needs a 240-volt circuit.

Electric whole-house units cost $500 to $1,500. The common sizes are 18, 24, 27 and 36 kW. The price gap between them is small; the difference in what they demand from your electrical service is large, which is why the unit price is misleading here more than anywhere. Each kilowatt raises about one gallon per minute by roughly 6.8 degrees, so a 27 kW unit delivers about 3.7 GPM at a 50-degree rise but only around 2.5 GPM at the 75-degree rise a northern winter demands.

Non-condensing gas units cost $700 to $1,500. They are simpler heaters with a single heat exchanger and a UEF of about 0.81 to 0.82. They look like the budget choice, and on the shelf they are. The catch is that their exhaust leaves hot enough that it must go through sealed stainless steel vent pipe, which is where most of the apparent saving goes.

Condensing gas units cost $1,200 to $3,000. A second heat exchanger pulls heat out of the exhaust, pushing UEF to roughly 0.93 to 0.98 depending on model, and leaves the exhaust cool enough to vent through PVC. Units with built-in recirculation pumps and buffer tanks sit at the top of the range. Propane versions cost about the same as natural gas versions, but they are separate models and are not interchangeable without a conversion kit, so order the one that matches your fuel.

Size moves price less than you would expect. A 199,000 BTU gas unit usually costs only a little more than a 150,000 BTU unit from the same line, so the common mistake is not overspending on capacity but buying too little of it. Work out your real requirement first with our guide to what size tankless water heater you need, then price the units that meet it.

3. What Drives Installation Cost

Base labour for a straightforward swap is four to eight hours for a licensed plumber, which at typical rates of $75 to $150 an hour comes to roughly $500 to $1,200. The swap is rarely straightforward, though, and the following items are where quotes diverge.

Gas line upsizing

A 40,000 BTU tank and a 199,000 BTU tankless heater are very different loads. Many houses have a 1/2-inch line to the water heater that cannot carry a full-size tankless unit over any real distance, so the line is upsized to 3/4-inch, sometimes all the way back to the meter. Expect $150 to $500 for a short run and $500 to $2,000 or more for a long or awkward one through finished space. Occasionally the utility also has to swap the meter or regulator for a higher-capacity one, which can add cost and delay.

Venting conversion

The old tank's flue cannot be reused. Condensing units vent through PVC or polypropylene, typically $200 to $600 installed for a simple sidewall run. Non-condensing units need Category III stainless steel, commonly $600 to $1,500 and more for a long or vertical route. That gap is why a condensing unit that costs $600 more on the shelf often produces the cheaper project.

Electrical work

Gas units only need a standard 120-volt outlet nearby, often under $300 if one is not already there. Whole-house electric is a different scale entirely. A 24 kW unit draws about 100 amps across two dedicated 240-volt circuits, and a 36 kW unit about 150 amps across three, on heavy copper wire. That is why manufacturers specify 150 to 300 amps of total service. New circuits run roughly $500 to $1,500; a service upgrade to 200 amps or more typically costs $1,500 to $4,000 and sometimes more where the utility has to replace the drop.

Permits, removal and the small parts

Permits and inspection usually cost $50 to $500 depending on your jurisdiction. Hauling away the old tank adds $100 to $500. Isolation valves for descaling add $100 to $200 and are worth every cent. A condensing unit needs a drain for its acidic condensate, and many areas require a neutraliser kit at $50 to $150. Put together, these small items routinely add $400 to $1,000 to a quote that looked complete.

4. Retrofit vs New Construction

Almost every cost driver above is a retrofit cost. In new construction the gas line is sized for the tankless load from the start, the vent is planned through the wall before it is finished, and the electrician sizes the service with the heater in mind. The incremental cost of choosing tankless over a tank in a new build can be a few hundred dollars to roughly $1,500, which makes it a much easier decision than converting an existing home.

Retrofits also carry a hidden chimney problem. If your old gas tank shared a masonry chimney with a furnace, removing the tank can leave the furnace venting alone into a flue now too large for it, which can cause condensation and draft problems. Codes often require a liner when that happens, and a lining job can add $1,000 or more. Ask any installer whether your furnace will be orphaned before you sign.

Location is the other big variable. Mounting the tankless unit exactly where the tank stood is cheapest, because the water lines are already there. Moving it to an exterior wall to shorten the vent, or closer to the bathrooms to cut the wait for hot water, is often worth doing, but every extra foot of gas line, water line and wiring is billed.

The practical lesson is timing. If you are already renovating a bathroom, finishing a basement or upgrading the electrical service for a heat pump or EV charger, much of the tankless retrofit premium disappears into work you are paying for anyway. If your tank fails on a Sunday and you need hot water by Tuesday, a like-for-like replacement is usually the sensible call, and tankless can wait for a planned project.

5. Operating Cost: Tankless vs a Tank

Tankless saves money by eliminating standby loss, the energy a tank spends keeping 40 to 80 gallons hot around the clock. The Department of Energy puts the saving at 24 to 34 percent for homes using 41 gallons or less a day, falling to 8 to 14 percent for heavy users around 86 gallons a day. ENERGY STAR estimates a certified gas tankless unit saves a family of four about $95 a year against a standard gas tank.

Our own rough model agrees. We assumed a family of four using about 64 gallons a day with a 70-degree temperature rise, natural gas at $1.50 a therm and electricity at 17 cents a kWh, and applied each heater's rated UEF. Your rates will differ, so treat this as a shape rather than a quote.

Two things jump out. First, gas tankless saves roughly $80 to $115 a year against a gas tank, which is real money but not life-changing. Rated UEF also flatters tankless slightly, because frequent short draws waste some heat in warm-up, and a recirculation pump adds its own running cost. Second, electric tankless barely beats an electric tank at all, since an electric tank is already efficient at converting power to heat; it only loses to standby, which is a small slice of its bill.

The heat pump line is the one most electric-home owners should notice. A heat pump water heater moves heat rather than making it, and in our model it costs about a quarter of what either electric option does to run. If you heat water with electricity and want lower bills, our heat pump water heater picks are the better place to spend the money.

6. The Payback Math, Done Honestly

Take the most common case: a 12-year-old gas tank is due for replacement and you are weighing a condensing tankless. A new gas tank installs for roughly $2,000 to $3,000. The condensing tankless retrofit installs for roughly $4,000 to $6,000. The premium is about $2,000 to $3,000, and the energy saving is about $100 a year. On energy alone, that is a 20 to 30 year payback on an appliance rated to last about 20.

That is not the whole picture, though, because lifespan changes the arithmetic. A tank typically lasts 8 to 12 years and a well-maintained tankless 20 or more, so over two decades you would probably buy two tanks to one tankless. Counting the avoided second tank, the lifecycle costs come out roughly even, with tankless slightly ahead if you descale it yourself and slightly behind if you pay a plumber every year.

Electric homes look worse. Swapping an electric tank for an electric tankless saves about $50 a year in our model, and if it needs new circuits or a service upgrade it will never pay back. The same budget spent on a heat pump water heater saves several hundred dollars a year and typically pays back in three to six years. On cost alone, there is no contest.

So who should buy tankless on cost? Households that will stay 15 years or more, already have adequate gas supply and a good venting route, and value endless hot water and the freed-up floor space. If you only want the cheapest hot water over the next decade, a new tank from our best gas water heater guide is usually the better spend, and our tankless pros and cons breakdown covers the non-financial reasons to choose either.

7. Rebates and Tax Credits in 2026

The federal tax credit most buyers remember is gone for new installs. The Energy Efficient Home Improvement Credit, section 25C, used to pay 30 percent of the cost of a qualifying high-efficiency gas tankless heater, up to $600. The One Big Beautiful Bill Act, signed in July 2025, ended it for property placed in service after December 31, 2025, and the IRS confirms it cannot be claimed for anything installed in 2026.

If your heater was installed and running by the end of 2025, you can still claim the credit on your 2025 return using Form 5695. Tax law changes, so check the current position at IRS.gov or with a tax preparer before you count on any federal credit, either way.

Utility rebates are now the main incentive for gas tankless. Many gas utilities pay roughly $100 to $400 for an ENERGY STAR certified unit, which for gas tankless means a UEF of at least 0.95, in practice a condensing model. Search the ENERGY STAR rebate finder and your utility's website before you buy, because some programmes require pre-approval or a participating contractor.

The larger federal money now goes to heat pumps instead. The state-run Home Electrification and Appliance Rebate programmes pay up to $1,750 toward a heat pump water heater for income-qualified households, but they do not cover gas tankless, and rollout varies widely by state. If you qualify, that rebate can make a heat pump unit far cheaper than any tankless project.

8. Maintenance Cost Over the Life of the Heater

Tankless heaters need descaling, usually once a year and more often in hard water, because calcium builds up inside the heat exchanger and eventually makes it overheat and fail. A plumber typically charges $150 to $350 for the service. Doing it yourself costs a one-time $60 to $120 for a small submersible pump, hoses and a bucket, plus a few dollars of descaling solution or white vinegar each year, and our guide on how to flush a tankless water heater walks through the job.

Over 20 years, that difference is real. Paying for annual professional service adds roughly $3,000 to $7,000, which is enough to wipe out the energy saving of a gas tankless entirely. DIY descaling keeps the lifetime maintenance bill to a few hundred dollars. This is the single biggest swing factor in whether tankless works out cheaper than a tank in your house.

Hard water raises the cost further. Once water passes roughly 7 grains per gallon, annual descaling may not be enough, and Rinnai, for one, publishes a hardness limit of 200 mg/L, about 12 grains per gallon, and a scale-inhibiting filter or a whole-house softener becomes a sensible part of the budget. A softener costs more up front but protects every appliance in the house; our water softener rankings cover the options. Condensing units also need the condensate neutraliser media replaced every few years, typically $20 to $60.

Repairs after warranty are the last line item. Igniters, flow sensors, fans and control boards on gas units usually cost $150 to $600 to replace with labour, and heat exchanger warranties commonly run 10 to 15 years on residential models. Budget for one or two minor repairs over the heater's life, then compare finalists on warranty terms in our best tankless water heater guide before you buy.