WHAT A WATER HEATER INSTALLATION REALLY COSTS IN SOUTHERN NEW HAMPSHIRE (2026) — FROM THE CREW THAT INSTALLS THEM EVERY WEEK
After 22 years installing water heaters across southern New Hampshire, we can tell you the honest answer to “what’s it going to cost?” is: it depends on your house — but it depends in predictable ways. Here’s how we actually price a water heater install, what makes one Derry home $3,000 and the next one more, and when tankless is worth it here (and when it isn’t).
QUICK ANSWER
A standard tank water heater installation with Paul the Plumber typically runs $3,725-$8,944 installed. A tankless system typically runs $5,915-$8,442 installed, depending on fuel type and what your home’s gas, venting, and electrical can support. Financing is available, and every install carries our 2-year parts and labor warranty (3-year for Paul’s Promise Plan members).
Our Pricing — Paul the Plumber
| Installation | Our range | What it covers |
| Tank water heater (replace like-for-like) | $3,725-$8,944 | New tank, code-required fittings (expansion tank, pan, valves as needed), haul-away, permit |
| Tankless water heater | $5,915-$8,442 | Unit, venting, condensate, descale-ready isolation valves, permit |
| Gas line / venting / electrical upgrades | Quoted with the job | Some homes need them, some don’t — we tell you before any work starts |
| These are our real ranges once confirmed — not scraped web numbers. Your exact price comes from looking at your actual mechanical room. |
WHAT ACTUALLY MOVES THE PRICE — FROM THE JOBS WE SEE
These run in parallel; a straightforward swap touches none of them, a conversion touches several.
Like-for-like vs. conversion. Swapping a tank for a tank is the friendly end of the range. Converting tank → tankless means venting, gas line sizing, and sometimes electrical — that’s the wide part.
Your gas line and venting. Tankless units pull a lot of BTUs on demand. Plenty of southern NH homes have gas lines sized for the old tank, not for a tankless — upsizing is real money and we check it before quoting, not after.
Where the heater lives. A walk-up basement in Londonderry prices different than a crawlspace or a closet install with tight venting runs.
New Hampshire’s cold groundwater — the spec nobody talks about. Incoming water here runs cold much of the year, and a tankless unit’s flow rating drops as the temperature rise increases. A unit that delivers plenty of hot water in a mild climate can come up short in an NH January — so we size for winter, not for the brochure. That’s an experience lesson, not a spec-sheet one.
Well water. A large share of NH homes run on private wells; sediment and hard water shorten heater life and can steer the tank-vs-tankless decision (more on that in our maintenance and filtration guides).
Recently, a customer was surprised that they had to upsize their gas line. They had a large tank style unit, and figured it would work for a tankless as well. It turns out that the gas line they currently had was actually undersized for the existing tank. These are things that are important to take care of, and it’s why all of our technicians make sure they do everything to code. Those code updates are also verified because we pull permits and get inspections on all of our jobs that involve gas. That ensures the job is done right, and our customer’s homes and families are safe.
TANK OR TANKLESS IN NH? OUR HONEST TAKE
Tankless wins on lifespan (~20 years vs. 8–12 for tanks, per HomeAdvisor) and efficiency (24–34% for typical households), and it frees up floor space.
A tank still makes sense when the budget is tight, the home’s gas/venting would need major upgrades, or recovery demand is modest.
In our service area specifically: hard well water scales tankless heat exchangers — if you go tankless on a well, plan on the annual descale (see our maintenance guide). We’ll tell you straight if your water needs treatment first.
SIGNS YOUR WATER HEATER IS ON ITS WAY OUT
8–12+ years old (check the serial plate — we’ll decode it for you)
Rusty or rotten-egg-smelling hot water
Rumbling/popping (sediment boiling in the tank)
Moisture or weeping around the base — replace before it lets go in the finished basement
GET A STRAIGHT ANSWER ON YOUR WATER HEATER
Paul the Plumber is family-owned and has served southern New Hampshire for over 22 years — Derry, Londonderry, Nashua, Merrimack, Hudson, Salem, the Seacoast, and greater Concord. Licensed (NH Master Plumber #3853), rated 4.8 on Google with 2,900+ reviews, with a 2-year parts & labor warranty on every install and financing available. *We treat our customers like family.*
Call (603) 437-7039 or book at paultheplumbernh.com.
FREQUENTLY ASKED QUESTIONS
How much does a water heater installation cost in southern NH?
With Paul the Plumber, a tank installation typically runs $3,725-$8,944 and tankless $5,915-$8,442 installed — the exact price depends on fuel, venting, and your home’s setup, confirmed before any work starts.
Is tankless worth it in New Hampshire?
Often, yes — roughly 20-year lifespan and better efficiency — but NH’s cold incoming water means sizing matters more here than in mild climates, and hard well water needs a treatment plan. We size for winter and tell you honestly if a tank is the smarter buy.
Do you handle the permit?
Yes — permits and inspections are part of the job.
What warranty do I get?
2-year parts and labor on every installation — 3-year for Paul’s Promise Plan members.
