Polly Plumbing | 1762 Keller Pkwy, Keller, TX | (817) 286-3446. Written by Haven Brady, Co-Founder. Locally owned, not a franchise. Every diagnosis on our trucks gets reviewed by a licensed master plumber. Texas License RMP-42199. Serving Keller, Southlake, North Richland Hills, Grapevine, Flower Mound, Fort Worth, Arlington, Trophy Club, Roanoke, and all of Tarrant County.
In one June stretch we installed three tankless water heaters around Keller. Three houses, three invoices, and the largest bill was more than double the smallest. Nobody got overcharged and nobody got a favor. The three jobs were simply not the same project wearing the same name.
That is the thing the internet will not tell you about tankless water heater cost. Search it and you will find confident numbers from under two thousand dollars to well past ten, all presented as the price of the same thing. They are not describing the same thing. Some mean the box on the wall. Some mean swapping a tankless for a tankless. Some mean the real project: converting a tank home to tankless for the first time, gas line and all.
This guide sorts those apart. If you are still deciding whether tankless belongs in your house at all, start with our tankless vs tank guide for Keller TX, which runs the honest fifteen-year math. This article is for the next step: you are pricing the project, and you want to know what actually moves the number.
Tankless Water Heater Cost in Keller: The Honest Bands
We keep pricing in broad strokes on purpose, because two identical units can land in two very different projects. The shape of it:
Replacing an existing tankless with a new one is the friendly version. The gas line, venting, and condensate path already exist, so the job is mostly the unit and a day of skilled labor. These land in the mid four figures for most homes.
Converting from a tank to tankless for the first time is a different animal. The unit is the smallest line on that quote. Gas line upsizing, new venting, a condensate path, isolation valves, relocation, permit, and inspection stack on top. First-time conversions climb well past the swap price, into five-figure territory for plenty of Keller homes.
Installing a unit you bought yourself trims the equipment margin but changes the warranty picture, which gets its own honest section below.
Whichever version yours is, the rules do not move: the written quote is the invoice, the $89 dispatch fee is waived for PollyCare members, and there is no emergency surcharge. For the tank-side comparison, our water heater replacement cost guide covers that half of the decision.
Swap or Conversion: The Fork That Sets the Price
Every tankless quote starts with one question: has this house done this before?
A house that already runs tankless has paid its infrastructure dues. The gas line was sized for it years ago. The vent penetration exists. The condensate drain exists. Replacing the unit is real work, but it is contained work.
A tank house has none of that. A tank sips gas all day and stores the result. A tankless unit gulps gas on demand, needs a vent built for its exhaust, and, if it is a condensing model, produces water that has to drain somewhere. Converting means building all three systems, which is why the same unit that swaps affordably in one house becomes a five-figure project two streets over. Neither quote is wrong. They are different projects.
The Gas Line Nobody Mentions
Here is the line item that surprises almost everyone, and the reason we assess it before quoting anything.
A typical tank water heater burns like a large stovetop burner. A whole-home tankless unit burns like a small furnace, several times the fuel demand, all at once, on top of everything else your gas system feeds. The half-inch gas line that fed your tank for twenty years often cannot feed a tankless at full fire, especially at the end of a long run from the meter.
An undersized line does not fail loudly. It starves the unit quietly: error codes in January, lukewarm water when two showers run, a system that never quite delivers what the brochure promised. The fix is upsizing the line, sometimes from the meter itself, and when the meter is the bottleneck, that upgrade runs through Atmos Energy, which we coordinate as part of the job.
This matters double around here. As our tankless vs tank guide covers, the outdoor kitchen and generator boom across Keller and Southlake has pushed plenty of gas systems near capacity already. A tankless added to a crowded line inherits every one of those problems. Gas work is licensed, permitted, pressure-tested work, and our gas line repair guide for Keller TX covers that side of the house. Any tankless quote that never mentions your gas line is not a complete quote. It is a down payment on a callback.
Venting, Condensate, and the Quiet Line Items
Two more systems ride along on every conversion.
Venting. Tankless exhaust does not use your old tank’s flue. Non-condensing units run hot exhaust through sealed stainless venting. Condensing units run cool enough for PVC, which is cheaper to route, and recover so much heat that they sip noticeably less gas doing the same work. Either way, a new penetration gets built, flashed, and inspected.
Condensate. Condensing units wring extra heat out of the exhaust, and the byproduct is a steady drip of acidic water that needs a proper drain path and a neutralizer cartridge. If that sounds familiar, it should. It is the same discipline as the AC condensate lines we spend every July clearing, and our AC drain line guide shows what happens when a condensate path gets treated as an afterthought. We route them right the first time.
Small items finish the list: isolation valves for future service, a drain pan where location demands one, haul-off of the old tank, the permit, and the city inspection. Individually small. Collectively, the difference between bids.
What Size Tankless Water Heater for a Keller Home
Tankless sizing is a flow budget, measured in gallons per minute, and the honest version has a season attached.
Add up what runs at once on your worst morning. Two showers and a kitchen tap is a very different budget than one shower and patience. Then remember that a tankless unit does not make hot water, it makes a temperature rise, and the rise it must produce depends on the water coming in. North Texas incoming water runs warm in summer and meaningfully colder in January, which is exactly when long showers happen. Size for January, not July. A unit that flexes in winter is the number one source of tankless regret, and it is a sizing mistake, not a technology failure.
Big floor plans get one more honest note: a garage-mounted unit sixty feet of pipe from the far bathroom will make that bathroom wait for its hot water, tankless or not. Recirculation options fix it and belong in the conversation up front, not as a surprise later.
Hard Water and Tankless: The 15 to 25 Grain Problem
The City of Keller’s water quality reports put local hardness at 15 to 25 grains per gallon, among the hardest water in Texas. Inside a tankless heat exchanger, that mineral load plates onto the very surfaces doing the heating. Scale insulates, efficiency drops, the unit works harder, and an unmaintained heat exchanger in our water can cut the famous tankless lifespan down toward ordinary.
Two habits protect the investment. Isolation valves installed on day one, which make the annual descaling flush a simple service instead of a plumbing project. And the flush itself, every year, no skipping. One of those June installs bundled the unit with its first descale service on the same visit, which is exactly the rhythm we recommend. A water softener changes the math further, slowing scale in every appliance in the house at once, and our water softener guide for Keller TX runs that decision honestly. When a tankless unit does start acting up, our tankless water heater repair guide covers the repair-or-replace call.
Polly Plumbing is a locally owned shop on Keller Parkway. We install, service, and repair tankless systems across Keller and Tarrant County, and every quote comes in writing with the gas line assessment included.
Brands We Install and the Ones We Will Not
Opinion, stated plainly. We install Rinnai and Navien, because both build serious heat exchangers and both keep parts flowing through professional supply houses. That means a repair in year twelve is a part order instead of a scavenger hunt.
We do not install the box-store house brands, and we would rather lose that job than attend its service calls. A tankless unit is a twenty-year relationship with a machine that fires like a small furnace. The brand question is really a parts-and-support question, and the answer shows up in year eight, long after the sticker price stopped mattering.
Buying Your Own Unit: The Honest Take
One of those June installs was an owner-supplied unit, so let’s talk about it without the usual defensiveness.
Buying your own tankless and paying for professional installation can make sense, especially on a straightforward swap where you found a genuinely good price on a brand we would install anyway. Labor-only pricing is smaller, and we will quote it honestly.
Go in with eyes open on three points. First, sizing risk moves to you: if the unit cannot cover your January flow budget, the install was perfect and the showers are still lukewarm. Second, warranty terms change. Manufacturers commonly require professional installation and registration for full coverage, and with an owner-supplied unit, the equipment warranty runs through your purchase, not our supplier relationship. We warranty our workmanship either way; the box is your relationship with the manufacturer. Third, the infrastructure math does not care who bought the box. The gas line, venting, and condensate work cost the same, which is why owner-supplying saves real money on swaps and surprisingly little on first conversions.
Why Two Tankless Quotes Differ by Thousands
Same house, same unit, quotes thousands apart. Before assuming anyone is a crook, read the scopes side by side.
The lowest bid is very often the least complete one. Check every quote for these lines: gas line assessment and any upsizing, venting scope, condensate routing and neutralizer, isolation valves, drain pan, old unit haul-off, the permit and inspection, and the first descale or a maintenance plan. A quote missing three of those is not cheaper. It is unfinished, and the missing lines return as change orders or as January error codes.
Then the usual business realities apply, licensed labor, insurance, warranty backing, overhead, same as any trade. Two complete quotes from real companies will still differ. Two quotes thousands apart usually differ in what they include, and the scope tells you which one respected you.
Install Day, Hour by Hour
A swap usually finishes in a day: old unit out, connections made, unit mounted and commissioned, hot water back by dinner. A conversion runs longer, sometimes two days, because the gas, venting, and condensate systems get built before the unit ever fires. Either way the city inspects the work, you get a walkthrough of the valves and settings, and a written summary lands with you the same day, like every Polly visit. Plan around a day without hot water for a swap and a bit more for a conversion, and we tell you which before anything is scheduled.
Around the Area
The project changes shape by neighborhood. The large floor plans across Southlake and Colleyville push sizing and recirculation to the front of the conversation, and their loaded gas systems make the line assessment non-negotiable. North Richland Hills’ older homes carry the area’s smallest original gas systems, so conversions there lean hardest on the upsizing question. Flower Mound permits through the Town, which we handle like Keller’s. And everywhere, the newer the house, the more likely the happy surprise: some newer builds were plumbed with tankless in mind, and those conversions land gentler than their owners feared.
We Are Close By
Polly Plumbing installs and services tankless water heaters from our shop on Keller Parkway, serving Keller, Southlake, North Richland Hills, Flower Mound, Fort Worth, Arlington, Trophy Club, Roanoke, and all of Tarrant County.
Pricing a tankless project, or holding a quote that never mentioned your gas line? Call (817) 286-3446. Live agents answer 24/7, the assessment comes before the number, and the written quote is the invoice.
Frequently Asked Questions About Tankless Water Heater Cost in Keller
How much does a tankless water heater cost installed in Keller TX?
It depends on which project yours is, and the spread is real. Replacing an existing tankless, where the gas line, venting, and condensate path already exist, lands in the mid four figures for most homes. Converting a tank home to tankless for the first time adds gas line upsizing, new venting, condensate routing, valves, permit, and inspection. That climbs well past the swap price, into five-figure territory for plenty of Keller homes. The unit is usually the smallest line on a conversion quote. Call Polly Plumbing at (817) 286-3446 for a written number after the assessment.
Why do tankless installation quotes vary so much?
Two reasons. First, quotes describe different projects: a swap and a first-time conversion can differ by multiples, honestly. Second, quotes include different scopes. The lowest bid is very often missing lines: the gas assessment, venting, condensate routing and neutralizer, isolation valves, haul-off, permit, or the first descale. Those missing lines return later as change orders or error codes. Read scopes side by side before comparing numbers, and treat a quote that never mentions your gas line as incomplete. Call (817) 286-3446 and we will put the full scope in writing.
Do I need a bigger gas line for a tankless water heater?
Very possibly, and it is the most commonly skipped line item in the trade. A tankless unit demands several times the fuel of the tank it replaces, all at once, on top of everything else on your gas system. The half-inch line that fed a tank for decades often starves a tankless, producing winter error codes and lukewarm water rather than obvious failure. The fix is upsizing the run, sometimes from the meter, and meter upgrades coordinate through Atmos Energy. Every Polly Plumbing tankless quote includes the gas assessment. Call (817) 286-3446.
How long does a tankless water heater last in hard water?
The twenty-year reputation is earned, but it is conditional in Keller’s 15 to 25 grain water. Scale plates onto the heat exchanger, and an unmaintained unit in our water can lose much of its lifespan advantage. Two habits protect it: isolation valves installed on day one, and an annual descaling flush, no exceptions. A water softener slows scale across the whole house and changes the math further. Maintained properly, tankless outlasts tank units by roughly double around here. Neglected, the gap closes fast.
What size tankless water heater does my house need?
Size to your worst winter morning, not a brochure. Add up the fixtures that genuinely run at once, then remember the unit produces a temperature rise, and January’s colder incoming water demands a bigger one than July’s. Undersizing is the number one source of tankless regret, and it is a planning mistake, not a technology failure. Large floor plans should also talk recirculation up front, because a distant bathroom waits on pipe length regardless of how the water gets heated. Call Polly Plumbing at (817) 286-3446 for a sizing visit before anyone quotes a model number.
Can I buy my own tankless unit and just pay for installation?
Yes, and sometimes it makes sense, especially on a straightforward swap with a good price on a brand worth installing. Know three things going in. Sizing risk moves to you, and an undersized unit performs poorly no matter how well it is installed. Manufacturer warranties commonly require professional installation and registration, and with an owner-supplied unit the equipment warranty runs through your purchase. And the infrastructure work, gas, venting, condensate, costs the same regardless of who bought the box, so owner-supplying saves the most on swaps and the least on conversions. We quote labor-only honestly. Call (817) 286-3446.
Does a tankless water heater need annual maintenance?
In Keller water, yes, without negotiation. An annual descaling flush clears the mineral scale off the heat exchanger before it insulates the unit into early aging. Isolation valves installed at the start turn that flush into a quick service call instead of a project. Skipping the flush in 15 to 25 grain water is how a twenty-year unit becomes a twelve-year unit. Bundle the first descale with the install, put the next one on the calendar, and the lifespan math that justified the project stays true. Call Polly Plumbing at (817) 286-3446.