Tankless water heater installation in Knoxville, TN.
Endless hot water, lower energy bills, and a unit that lasts twice as long as a tank. Hard Knox Plumbing installs, repairs, and maintains tankless (on-demand) water heaters for homes across Knoxville and everywhere within 25 miles — Farragut, Hardin Valley, Oak Ridge, Maryville, and beyond.
Every installation is done by a licensed, insured technician, sized correctly for your household, and backed by our warranty. Financing is available, and we answer the phone 24/7.
Tired of Cold Showers?
Hot water that never runs out — heated only when you need it.
A traditional tank heater keeps 40–50 gallons hot around the clock, whether you use it or not — and when it's empty, you wait. A tankless (on-demand) water heater heats water the instant a tap opens, so the third shower of the morning is as hot as the first.
Because it only runs when you're using hot water, a tankless unit typically cuts water-heating energy use significantly — and it hangs on a wall, freeing up the floor space a bulky tank used to claim. Most quality units last 20+ years, roughly double the life of a standard tank.
The catch: sizing and installation matter. A unit rated too small for your household's peak demand will disappoint, and gas lines, venting, and Knoxville's hard water all need to be handled correctly. That's exactly what we do — we assess your home, recommend the right unit, and install it to code the first time.
Repairs and maintenance too. Already have a tankless unit? We service all major brands — including the annual flush and descale that Knoxville's hard water makes essential.
Why Go Tankless
What Knoxville homeowners get out of the upgrade.
Endless hot water
Back-to-back showers, laundry, and dishes at the same time — the water stays hot because it's heated on demand, not stored.
Lower energy bills
No energy wasted keeping a tank of water hot 24/7. Heating on demand trims water-heating costs month after month.
Space-saving design
About the size of a suitcase and wall-mounted — reclaim the closet, garage corner, or utility space a 50-gallon tank occupied.
20+ year lifespan
Roughly double the life of a standard tank, with no tank to rust through and flood your home when it fails.
What to Expect
How a tankless installation works with us.
Most installations are completed in a single day. Here's the process from first call to hot water.
In-home assessment
We measure your household's peak hot water demand, check your gas line, electrical, and venting, and recommend the right unit — with a clear, upfront price.
Removal & prep
We drain and haul away your old tank, then run any gas, venting, or water line upgrades the new unit needs — all to current code.
Install & test
We mount the unit, make every connection, then test flow, temperature, and safety at every fixture before we call it done.
Walkthrough & warranty
We show you how to use and maintain the unit, register your manufacturer warranty, and back the whole job with our own workmanship warranty.
Upfront pricing. Flexible financing.
A tankless unit costs more upfront than a tank, then pays you back in energy savings and a longer life. We quote the full installed price before work begins — no surprises — and financing lets you spread the cost into easy monthly payments.
Common Questions
Tankless water heater FAQs.
How much does a tankless water heater cost in Knoxville?
Total installed cost depends on the unit's capacity, fuel type (gas or electric), and whether your home needs gas line, venting, or electrical upgrades. Because those variables matter, we give every homeowner a firm, written quote after a free in-home assessment — and the price we quote is the price you pay. Financing is available to spread the cost into monthly payments.
How long does installation take?
Most tankless installations are finished in one day, including removing your old tank. If your home needs a gas line upsize or new venting, we'll tell you at the assessment and schedule accordingly — you'll never be left without hot water overnight unexpectedly.
Do tankless heaters work with Knoxville's hard water?
Yes — but East Tennessee's mineral-heavy water causes scale buildup inside the heat exchanger over time. An annual professional flush and descale keeps the unit at peak efficiency and protects the manufacturer warranty. We offer this as a standalone service, and it's included for Hard Knox Home Club members. Pairing the unit with a water filtration or softening system helps too.
Gas or electric — which should I choose?
Gas units deliver higher flow rates and usually cost less to run, making them the common pick for whole-home use — but they need proper venting and an adequately sized gas line. Electric units are simpler to install and great for smaller demands or point-of-use spots. We'll assess your home's existing systems and give you a straight recommendation, not an upsell.
What size tankless unit does my home need?
Tankless units are rated by flow rate (gallons per minute) at a given temperature rise. We total up your realistic peak demand — say, two showers plus a dishwasher running at once — and match a unit that handles it with headroom. An undersized unit is the #1 cause of tankless disappointment, and it's entirely avoidable with correct sizing.
Is the work warrantied?
Yes. Every installation carries the manufacturer's warranty on the unit plus Hard Knox Plumbing's own workmanship warranty — our promise that you'll never call us twice for the same issue. We're licensed and insured, and we install to code so your warranty and your home inspection both hold up.
Recommended by your neighbors.
“My cost was exactly what he told me over the phone. He was on time, cleaned up after the repair and was very courteous. Hard Knox Plumbing will always be my first call.”
“As I expected, my call was answered by someone who actually knew what my problem was. Danny was able to work me in today.”
“It was an amazing service. They were on time, on budget and great to work with. Very knowledgeable, very friendly, and a reasonable price.”
From the blog
Straight answers on water heaters.
Related Services
More ways we keep your water working.
Standard Water Heaters
Not ready for tankless? We repair and replace traditional tanks too, sized right for your household.
Learn more →Water Filtration Systems
Soften hard water to protect your new tankless unit — and get cleaner water at every tap.
Learn more →Hard Knox Home Club
Members get the annual tankless flush included, plus priority scheduling and repair discounts.
Learn more →Your Local Tankless Experts
Serving Knoxville and everywhere within 25 miles.
Hard Knox Plumbing is a locally owned company based at 3414 Henson Rd C, Knoxville, TN 37921 — owned by Danny Ferris and Jarrett Mohn. We install tankless water heaters across Knoxville, Farragut, Hardin Valley, Lenoir City, Oak Ridge, Loudon, Alcoa, and Maryville.
Call 865.765.8946 any time — a real person answers 24/7, including nights, weekends, and holidays.
No hot water right now?
We're open 24/7. Call us right now.
A failed water heater can't wait for Monday. A Hard Knox plumber answers around the clock — nights, weekends, and holidays.