$1,000 to $8,000 installed. Where you land is decided less by the heater than by what is already in the house. Swapping a tankless unit for another tankless unit in the same location is the bottom of that range. Converting from a tank heater — where the gas line, the venting and the water connections all have to change — is the top of it.
An electric unit is a different conversation again, and usually a smaller one, but it is limited in what it can supply and it is not a straight substitute for gas in a whole house.
Why we publish a range and not a price. Nobody can price this job from a web page, and any site that gives you one number is guessing. What we can do is tell you the band our own jobs actually land in, what pushes a job to each end of it, and what we would need to see to give you a real number. That is what this page does.
Why does converting from a tank cost so much more than the heater?
Because a tankless heater is not a heater swap. It is a heater, a gas job, a venting job and a plumbing job at once.
- Gas supply. A tankless unit fires much harder than a tank while it is running. The existing gas line is frequently undersized for that demand and has to be upsized, sometimes all the way back to the meter. This is the item that most often surprises people, and it is the one that most moves the price.
- Venting. Different from a tank, and it has to be run correctly to the outside.
- Water connections and mounting. The unit hangs on a wall. The lines move to meet it, and service valves go on so it can actually be flushed later.
- Where it is going. An attic install is more work than a garage wall, and it needs a pan and a drain done properly.
A tankless conversion is a heater, a gas job, a venting job and a plumbing job at once. The heater is the part everybody prices.
Is it actually worth it?
Straight answer: sometimes, and not always for the reason people expect.
It is worth it if you genuinely run out of hot water, if you want the floor space back, or if you are replacing a heater in an attic and would rather not have eighty gallons of water up there over your ceiling. Those are real reasons and we install a lot of them.
It is a weaker argument as a pure money-saving swap. It costs more up front than a tank, and the running savings arrive slowly. If a salesman tells you it pays for itself quickly, ask him to show you the arithmetic on your gas bill, not a brochure.
How long does a tank heater last here anyway?
Around ten to twelve years on our water. Box-store brands tend to go sooner. If yours is at that age and still working, you have time to decide properly rather than at seven in the morning with cold water and a flooded closet — which is when most of these decisions actually get made.
Which brands, and does it matter?
We sell and install State, Navien and Noritz. It matters for one practical reason: parts availability. We can generally get parts for what we stock inside a day. We are happy to service a Rinnai that somebody else installed, but parts for it come from further out — around three days — and three days is a long time without hot water.
That is worth knowing before you buy a unit online because it was cheaper, and it is worth asking any installer.
What does it cost to own, not just to install?
This is the part that gets left out of the sales conversation. A tankless heater needs descaling roughly once a year on our water. Skip it and the heat exchanger scales up, the unit starts short-cycling, and eventually you are paying for a repair or a replacement that annual maintenance would have avoided.
It is a job a confident homeowner can do with the right kit — we wrote the whole sequence out in how to flush a tankless water heater rather than keeping it to ourselves. If you would rather we did it, we do that too. Either way, budget for it.
What would you need to see to quote it?
The existing heater and where it lives, the gas meter and the line running to it, and where the unit would go. The gas supply question is the one that decides the number, and it cannot be answered over the phone.
See tankless water heaters, tank water heaters and gas line services. Ask for a quote and financing will be on it.
Common questions
How much is a tankless water heater installed?
Between $1,000 and $8,000 installed, and the spread is mostly about what is already there. Replacing a tankless unit with another tankless unit in the same spot is at the bottom. Converting from a tank heater, where gas line, venting and water lines all have to change, is at the top.
Why is converting from a tank so much more expensive?
Because a tankless unit fires far harder than a tank when it runs, so the existing gas line is often undersized for it and has to be upsized back to the meter. The venting is different, the mounting is different, and the water connections move. The heater is only part of what you are paying for.
Is a tankless heater worth it over a tank?
Sometimes. It is worth it if you actually run out of hot water, if you want the floor space back, or if you are replacing a heater in an attic and want to stop worrying about a tank up there. It is not automatically worth it as a straight money-saving swap - it costs more up front and the savings arrive slowly.
Which brands do you install?
State, Navien and Noritz. We will service a Rinnai somebody else installed, but be aware parts for it come from further out - about three days rather than one - which matters when you have no hot water.
Does it need servicing?
Yes, and this is the part people are not told at the point of sale. A tankless unit needs descaling roughly annually on our water, or the heat exchanger scales up and the unit starts short-cycling and eventually failing. Budget for it as an owning cost, not a surprise.
Can I finance it?
Yes. Financing is an option on the quote we send you rather than an application on this website. Ask for a quote and it will be on there.
Last updated · written by a licensed master plumber, MPL 38224