Tankless Water Heaters for New Hampshire Homes
A tankless (on-demand) water heater heats water only when there is a hot water demand, instead of keeping a 40 to 80 gallon tank hot around the clock. Modern condensing tankless units approach 96 percent efficiency and can supply endless hot water as long as the unit is sized to the home's peak demand. For many southern New Hampshire homes, the upgrade pays back in lower operating cost, longer equipment life, and recovered floor space.
At A.J. LeBlanc Heating, our licensed plumbers install and service tankless water heaters across NH. Below is what we tell customers thinking about the switch.
How tankless water heaters work
When you open a hot water tap, water begins flowing through the unit. A flow sensor fires the gas burner, which heats the water passing through a heat exchanger on its way to the tap. The unit modulates burner output to maintain a steady outlet temperature as flow rate changes. When the tap closes, the burner shuts off.
There is no storage tank, no standby losses, and no recovery time. The trade-off is that the unit must be sized to the home's peak simultaneous demand, the gallons per minute (GPM) needed when the most fixtures are running at once.
Efficiency and operating cost
Modern condensing tankless units typically achieve 0.92 to 0.96 UEF (Uniform Energy Factor), compared to 0.60 to 0.70 for traditional gas storage tanks. The combination of higher burner efficiency and zero standby losses produces meaningful operating cost savings, especially for households with moderate or low hot water use (where standby losses dominate).
Households with very high hot water use see proportionally smaller savings because the burner runtime dominates, but they still benefit from the efficiency improvement and the unlimited supply.
Sizing matters more than brand
The most common reason a tankless installation disappoints is undersizing. A unit that is too small for the home's peak demand will deliver lukewarm water when two showers run at the same time, or fail to keep up with a soaking tub.
Sizing depends on:
- Number of simultaneous hot water uses likely at peak (showers, kitchen sink, dishwasher, clothes washer)
- Incoming groundwater temperature (lower in NH winter, which reduces effective capacity)
- Desired output temperature at the fixtures
A licensed plumber sizes the unit using actual fixture flow rates and NH-specific winter groundwater temperatures, not the manufacturer's nominal GPM rating. A unit rated 11 GPM at a 35°F temperature rise may only deliver 6 GPM at the 75°F rise needed in a NH January.
Brands we install
Navien
Navien's NPE series is one of the most popular condensing tankless lines installed in NH homes. Strong build quality, very high efficiency, and a built-in recirculation option on some models that delivers near-instant hot water at distant fixtures.
Rinnai
Rinnai has a long track record in tankless and a very broad product lineup. Their condensing models are robust and widely supported. Older Rinnai units in NH homes are often still going strong after 15+ years.
Combi-boiler tankless
For homes with hydronic heat, some tankless units (most notably the Navien NCB combi-boiler) provide both space heat and domestic hot water from one wall-mounted unit. This can simplify mechanical room layout in NH retrofits.
Maintenance: descaling is not optional
The heat exchanger in a tankless water heater is sensitive to scale buildup. Hard water shortens unit life and reduces efficiency if descaling is skipped.
- Annual descaling is recommended for most installations.
- Homes on well water or with high mineral content may need it more often.
- Installation should include isolation valves on the hot and cold sides specifically to make descaling straightforward.
- A whole-home water softener significantly extends the time between required descalings.
Is tankless right for your home?
Tankless typically wins when:
- The existing water heater is past 10 years old and needs replacement
- The home has gas service (natural gas or propane) and adequate venting
- Peak hot water demand is moderate (2 to 3 simultaneous uses)
- The household values endless hot water and recovered floor space
A traditional storage tank may be the better choice when:
- The home's gas service or vent location makes tankless installation cost-prohibitive
- Peak simultaneous demand is very high and would require a large, expensive unit
- The home is all-electric (a heat pump water heater is usually better than electric tankless in NH)
Schedule a consultation
If you are evaluating tankless for your New Hampshire home, or your existing water heater is near the end of its life, contact A.J. LeBlanc Heating. Serving NH families since 1928.
Frequently Asked Questions
How long does a tankless water heater last?
15 to 20 years with annual descaling. Hard water shortens that significantly if descaling is skipped.
Can I run two showers at once with a tankless?
Yes, if the unit is sized for it. A correctly sized residential condensing tankless typically supports two simultaneous showers plus a kitchen sink in NH winter conditions. Undersized units cannot.
How much does tankless cost compared to a tank?
Installed cost is typically 1.5 to 2 times the cost of a comparable gas storage tank, driven by the unit, the gas line, and the venting. The lower operating cost and longer expected lifespan often close that gap over the life of the unit.
Do tankless units work in cold New Hampshire winters?
Yes. Incoming groundwater temperatures in NH winter drop to about 40°F, which means a tankless unit needs a larger temperature rise to deliver 120°F water than it would in a warmer climate. Sizing the unit for this is essential.
How often does a tankless need maintenance?
Annual descaling and a yearly inspection. Both are straightforward for a licensed plumber.