Tankless Water Heater Installation Cost Calculator
Converting a gas storage tank to a tankless water heater runs about $3,914 in Atlanta for a 4 gpm condensing unit — $2,722 to $5,106 — against $1,751 to fit another tank. The appliance is the small part. What you are really buying is a bigger gas pipe, a sealed flue that cannot share the old chimney, a dedicated electrical circuit and a condensate drain. And the size you need depends on how cold your water arrives: 140,000 BTU/h in the north against 80,000 in the south, for the same shower.
Estimate the cost for your home
Estimated cost of converting to a tankless water heater
$4,001
typical · range $2,806 to $5,196 · 4 gpm at a 55°F rise · 110,000 BTU/h of output · 120,000 BTU/h unit · 17 trade hours
Labour priced at national wages. Enter a ZIP code to price it for your area. 74% of this figure comes from modelled material prices — each line shows its own uncertainty.
Priced from bls.gov Aug 2026how every line is sourced
The one input that changes the answer for you.
The normal choice, and the one where the sizing arithmetic on this page matters most. What decides the job is not the appliance price but whether the existing gas pipe can deliver the flow — and at these inputs it frequently cannot.
The common conversion, and the one with the hidden cost: a domestic gas tank draws around 40,000 BTU/h and a tankless is by federal definition above 50,000 — in practice three to five times the tank. The pipe that fed the old one very often cannot feed the new one.
The middle of the range. Note that incoming temperature is a winter figure rather than an annual average: the unit has to work in January, not in June, and a heater sized on a summer measurement will disappoint exactly once a year for three months.
A shower and a sink at the same time. This is the number that sizes the appliance, and the one people get wrong in both directions — sized on the tank it replaces, which stores rather than heats, or sized on a summer measurement. Count the outlets that genuinely run together on a January morning, not the ones that could.
The common answer: the main run is adequate but the branch feeding the old tank is not. New pipe from a suitable point in the existing system to the new location, priced by the foot.
Cheapest and most common. Sealed pipe straight out, short run. What limits it is the termination: it cannot sit under a window, near an air intake, or where the plume will ice a path in winter.
From where the new pipe starts to the heater. A run from the meter is priced with an allowance for the extra fittings and drilling it takes to cross a house.
1 / 4
The figure above is already calculated. Each step just makes it more yours, and you can stop at any of them.
The same flow needs a different heater in a different climate
A tank stores hot water and does not care where the cold comes from. A tankless heats it as it passes, so the incoming temperature decides everything.
| Incoming water | Rise | Output needed | Unit size | Cost |
|---|---|---|---|---|
| 40°F | 70°F | 140,000 | 150,000 | $4,316 |
| 55°F | 55°F | 110,000 | 120,000 | $4,001 |
| 70°F | 40°F | 80,000 | 120,000 | $4,001 |
4 gallons a minute needs 140,000 BTU/h in the north and 80,000 in the south — the same shower, the same appliance, 75% more heat. The arithmetic is one line: flow × 500 × temperature rise, where 500 comes from a gallon of water weighing 8.33 pounds and a BTU raising one pound by one degree. ⚠️ It is a winter figure, not an annual average. A heater sized on summer groundwater disappoints once a year, for three months. This is the single most common reason somebody spends thousands and ends up with lukewarm water in January, and no part of the buying process mentions it. Where two rows share a price, they share an appliance: the requirement has fallen below the smallest unit that is made, so the warmer one is not cheaper — it simply gets more hot water out of the same machine.
Converting, against replacing the tank with a tank
| What you do | Trade hours | Cost |
|---|---|---|
| Another storage tank | — | $1,772 |
| Convert to tankless | 17 | $4,001 |
Converting costs 226% of a like-for-like tank swap — $2,229 more. Both figures come from models on this site at the same BLS wage for your area, which is the only reason the ratio is worth anything. ⚠️ What it does not include is the running cost, and we will not pretend to know it: what you save afterwards depends on your gas price, your electricity price and how much hot water the house uses, and none of the three is national or stable. The honest way to read this page is that the conversion has to be worth it for reasons other than the bill — endless hot water, twenty years instead of twelve, or the floor space the tank was standing on.
| Line item | Qty | Cost | Source |
|---|---|---|---|
| Condensing gas tankless heaterinput BTU ÷ 1,000, condensing | 1201,000 BTU/h input | $900–$1,620 | estimated±29% |
| Upsized natural gas pipe and fittingsfeet of new gas pipe, 1.6× when run from the meter | 25linear ft | $300–$750 | estimated±43% |
| Gas fitting, pressure test and purge1.5, 5 or 8 hours depending on how much gas pipe is run | 5hour | $298–$320 | sourced |
| Sealed plastic intake and exhaust1 on a condensing unit | 1each | $140–$380 | estimated±46% |
| Running the vent and making the penetration3 hours through a wall, 6 through the roof | 3hour | $179–$192 | sourced |
| Condensate drain and neutraliser1 on a condensing unit | 1each | $60–$180 | estimated±50% |
| Water connections and pressure relief1 per installation | 1each | $90–$240 | estimated±45% |
| Isolation valves for descaling1 when service valves are fitted | 1each | $70–$190 | estimated±46% |
| Dedicated circuit for the heater1 on a gas unit with a dedicated circuit | 1each | $70–$200 | estimated±48% |
| Electrical work2 hours on a gas unit, 7 on an electric one | 2hour | $118–$127 | sourced |
| Removal, mounting and commissioning7 trade hours, 5 when there is no old tank to remove | 7hour | $417–$448 | sourced |
| Old tank removal and disposal1 when the old tank is taken away | 1each | $45–$130 | estimated±49% |
| Plumbing, gas and mechanical permits1 when the job is permitted | 1each | $120–$420 | estimated±56% |
| Total | $2,806–$5,196 | ±30% |
Where these numbers come from
- The number nobody asks you for
- A storage tank keeps forty or fifty gallons hot and does not care where the cold water comes from. A tankless heats water as it flows past, so what it can deliver is set entirely by how far it has to raise the temperature. The arithmetic is one line — flow in gallons per minute × 500 × the rise in degrees — where the 500 is a gallon of water weighing 8.33 pounds times sixty minutes. The same 4 gpm needs 140,000 BTU/h where groundwater arrives near 40 °F and 80,000 where it arrives near 70 °F — 75% more heat for an identical shower. ⚠️ And it is a winter number, not an annual average: a heater sized on summer water works beautifully for nine months and disappoints for three. This is the most common reason somebody spends thousands and ends up with lukewarm water in January, and nothing in the buying process mentions it.
- Why the electric version is usually impossible
- Electricity is close to perfectly efficient at making heat, which is precisely the problem: the power has to arrive as amps. 4 gpm in a cold climate is 41 kW, or 171 amps at 240 volts. Compare that with the whole service into a typical house — 100, 150 or 200 amps for everything, heating, cooking, the dryer and increasingly the car. An electric whole-house tankless of that size is not an appliance you add; it is a reason to upgrade the service, and that job is priced on our electrical panel page rather than here. It is why electric tankless heaters are common as small point-of-use units and rare as whole-house ones anywhere cold. The calculator computes the amps for whatever you enter, so you can see the wall before you hit it.
- What the federal rules actually fix, and what they do not
- 10 CFR 430.32(d) defines this product class as Instantaneous Gas-fired Water Heater <2 gal and >50,000 Btu/h and sets its minimum uniform energy factor at 0.81. Two useful things fall out of that definition. First, the efficiency floor is high enough that a cheap tankless is not an inefficient one — the differences between models are features and durability, not fuel. Second, and more practically: the class begins above 50,000 BTU/h, while a domestic storage tank draws around 40,000. The appliance you are replacing burns a third of what the new one wants at full output. That single fact is why the gas pipe is the real question on this page and why it is the item most often missing from a quote given over the phone. Read the rule at 10 CFR 430.32, Energy and water conservation standards and their compliance dates, retrieved 2026-08-23, and the efficiency criteria at ENERGY STAR, Residential Water Heaters Key Product Criteria.
- Hard water, annual flushing, and wages
- A tankless heats water in a narrow passage at high intensity, which is exactly the condition that deposits scale. Where the water is hard, manufacturers expect an annual flush, and whether that is a twenty-minute job or a plumbing visit is decided at installation by two small valves. USGS Water Science School, Hardness of Water maps where that applies, retrieved 2026-08-23; if you are in a hard-water area, a softener changes the maintenance story for this appliance more than any feature on the box, and it is priced on our water softener page. Wages come from BLS OEWS, May 2025, for plumbers and pipefitters and for electricians, retrieved 2026-08-20, with benefit load from BLS ECEC.
- Material prices
- Modelled estimates, not sourced prices. No public, machine-readable source of US residential material prices exists, and we would rather say so than pretend otherwise. Each line carries its own uncertainty band. How we estimate them.
Contractor overhead and profit applied at 33–43% over direct cost. Data last reviewed 2026-08-23.
What this figure does not include
- An electrical service upgrade
- Every figure assumes the panel has room and capacity. For an electric tankless at these currents that is a strong assumption, and where it fails the upgrade is priced on our electrical panel page and is often larger than this whole job.
- A larger gas meter
- If the meter itself cannot deliver the total load, the utility replaces it, on their schedule and sometimes with their own charge. Worth one phone call before collecting quotes.
- A water softener
- In hard water a softener extends the life of a tankless heater considerably, and it is a separate appliance with its own price. It is on our water softener page.
- A recirculation loop
- The pump and return pipe that make hot water arrive quickly at a distant tap. Frequently wanted alongside a tankless and priced separately, because in an existing house the return pipe is the expensive part.
- Annual descaling
- Not in the figure and not optional in hard water. The isolation valves priced here are what make it a cheap job rather than an expensive one.
- A like-for-like tank replacement
- If you are replacing a tank with a tank, this is the wrong page — that is priced on our water heater page, and it is a fraction of anything here.
Questions people actually ask
Is it worth converting to a tankless water heater?
On price alone, usually not: converting is $3,914 in Atlanta against $1,751 for another storage tank — 224%, or $2,163 more. Both figures come from models on this site at the same BLS wage, which is the only reason the ratio means anything. We will not tell you what you save afterwards, because it depends on your gas price, your electricity price and how much hot water the house uses, and none of those is national or stable. The reasons that hold up are the other ones: hot water that does not run out, roughly twenty years of life instead of twelve, and the floor the tank was standing on. If the honest answer to "why" is the monthly bill, the arithmetic is doing less work than the sales pitch suggests.
What is the average labor cost to install a tankless water heater?
About $961 of the $3,914 total on this model — 17 trade hours at Atlanta rates for plumbers and electricians, benefit-loaded and with contractor markup. That is over half the job, which is the point of this page: you are not buying an appliance swap. The hours go into gas pipe, a sealed flue that cannot share the old chimney, a dedicated electrical circuit the gas tank never needed, a condensate drain, and isolation valves. Change one assumption and it moves: with the existing gas pipe reused the whole job is $3,191, and with a new line from the meter $4,398. A labour figure quoted before anybody has looked at the gas pipe is a guess.
How much does it cost to install a tankless water heater at Home Depot?
We do not have their price and will not invent one. What is worth knowing is the shape of a big-box quote: it is a flat rate, delivered by a local subcontractor, and it covers a defined scope — the appliance, the connection and the removal of the old one. The items that make a conversion expensive sit outside that scope and arrive as change orders after the survey. On this model they are the gas line ($1,207 between reusing the existing pipe and running a new one from the meter), the flue, the dedicated circuit and the condensate drain. Compare a flat rate against this breakdown line by line and ask which of them it includes, in writing, before the day.
How much does Lowe's charge to install a tankless hot water heater?
Same answer and the same advice: we do not publish other companies' prices, and a single national number for this job would be misleading anyway. The variation is not retail margin, it is your house. On this model the same 4 gpm heater is $3,191 where the gas pipe is already big enough and $4,398 where it has to come from the meter, $3,914 condensing and $4,021 not. What any flat-rate quote is really telling you is which of those cases it has assumed. Get the survey first, then compare — and if the meter itself cannot carry the extra load, that is the utility's work, on the utility's schedule, and nobody's installation price includes it.
Taken from Google’s “people also ask” results for this search on 2026-08-23, not invented.
Other cost calculators
The first of these are the jobs closest to this one — the ones that turn up in the same quote, or instead of it.
- Water softener installation cost
Sizes the unit from your actual water hardness and household size, and shows why a house without a softener loop costs twice the plumbing labour.
- Well pump replacement cost
Prices a replacement from the depth of your well, which drives the bill through three separate lines and one hard threshold at 250 feet.
- Interior painting cost
Converts your floor area into the wall area that actually gets painted, and then into gallons, which is the one line on a painting quote you can check afterwards.
- EV charger installation cost
Prices a charger by the route the cable takes, and compares load management against a service upgrade when the panel has no capacity.
- The full tankless water heater installation cost dataset
Every unit price, every quantity rule and the reasoning behind each estimate, as a plain table.
- How we calculate
The formula, the sources, and an honest account of which parts of the model are weak.