Is a Tankless Water Heater Worth It? Pros, Cons & Cost Savings

A gas tankless water heater can be a strong fit when the home values continuous hot water, wall-mounted equipment, and reduced standby loss. It is not automatically the best replacement for every gas-fired tank. A.J. LeBlanc Heating compares peak hot-water demand, incoming-water temperature, gas capacity, venting, installation cost, water quality, maintenance, and available alternatives before recommending one.

What "tankless" actually means

A tankless (or on-demand) water heater heats water as it flows through the unit, rather than keeping a 40 to 80 gallon tank hot around the clock. When you open a hot water tap, the unit fires and heats water on its way to the tap. When the tap closes, the unit shuts off. No standby tank, no continuous heat loss, no fixed gallons-per-recovery limit.

The honest pros

Continuous hot water when properly sized

As long as the unit is sized for the home's peak simultaneous demand, you cannot run out of hot water. Long showers, multiple back-to-back showers, and large soaking tubs all work fine. For families with teenagers or homes with high simultaneous hot water demand, this alone justifies the switch.

Potential for long service life

Service life depends on the model, water quality, maintenance, installation, use, and repair history. Tankless equipment can have a long service life when maintained according to its manual, but it should not be sold by assuming one unit always outlasts two storage tanks.

Compact, wall-mounted design

A tankless unit mounts on the wall and recovers the floor space a 40 to 80 gallon tank would have occupied. For NH homes with small mechanical rooms, this matters.

Lower operating cost

No standby losses from a stored tank means lower fuel use for water heating, especially for homes with moderate or low hot water use where standby losses dominate. Modern condensing tankless units reach 95+ percent efficiency.

Cleaner water at the tap

No tank means no sediment accumulating at the bottom of a stored tank for years, eventually finding its way to fixtures.

The honest cons

Higher upfront cost

Installed cost is typically 1.5 to 2x the cost of a comparable tank water heater. The price difference comes from the unit itself, the gas line (tankless units often need a larger gas supply line than a tank), and the venting (typically PVC sidewall venting for condensing units).

Gas line upgrade may be required

A tankless unit fires at high BTU input during use (typically 180,000 to 199,000 BTU/hr) compared to a tank's 35,000 to 75,000 BTU/hr. The existing gas line may not be sized for the higher instantaneous demand and may need to be upgraded.

Sized to peak simultaneous demand

If the unit is undersized for the home's peak hot water demand, the result is lukewarm water during high simultaneous use. Sizing matters more than for a tank, where storage capacity absorbs short demand spikes.

Cold-water sandwich on some models

The brief slug of cooled water between hot water draws can be noticeable at fixtures with intermittent use. Some manufacturers (notably Navien) include a built-in recirculation feature that minimizes this.

Model- and water-specific maintenance

Tankless units need maintenance based on the model and water quality. That may include inlet-filter cleaning, condensate inspection, and heat-exchanger flushing or descaling. Follow the selected unit's manual rather than assigning every home one interval.

Power requirement (electric ignition)

Tankless units require continuous electrical power for the ignition and electronics. During a power outage, even gas-fired tankless units stop producing hot water. A standby generator addresses this.

Where tankless wins

• NH homes with natural gas or propane service
• Families with moderate to high hot water demand (multiple bathrooms, teenagers, soaking tubs)
• Homes where mechanical room floor space is at a premium
• Replacing an aging tank that is already at end of life
• Owners planning to stay in the home long enough to capture the lifespan benefit

Where tankless does not win

• All-electric homes (a heat pump water heater is usually the better fit)
• Homes with very low hot water demand (the efficiency advantage is small relative to a small standard tank)
• Homes where the existing gas service cannot support the higher instantaneous demand without expensive upgrades
• Homeowners with short ownership horizons (the upfront premium does not have time to pay back)

Compare the complete ownership cost

Compare the installed proposals, current fuel rate, estimated hot-water use, equipment efficiency, maintenance, and expected ownership period. Reduced standby loss can lower fuel use, especially in lower-use homes, but the installation premium and gas or venting changes vary too much for one statewide payback calculation.

The alternative: heat pump water heater

In an all-electric home, a heat pump water heater is often worth comparing. It can use substantially less electricity than a standard electric-resistance tank, but space, temperature, noise, condensate, electrical capacity, hot-water use, and current rebate eligibility all affect the choice.

Schedule a water heater consultation

If your current water heater is approaching end of life, or you are considering an upgrade, contact A.J. LeBlanc Heating or call 603-623-0412. Our licensed plumbers will walk through which option fits your specific home, fuel, and demand pattern. Serving New Hampshire families since 1928.

Frequently Asked Questions

Is a tankless water heater really cheaper to run?

Reduced standby loss can lower fuel use, especially in lower-use homes. Actual savings depend on hot-water use, equipment efficiency, fuel rates, installation, and maintenance.

How long does a tankless water heater last?

Service life depends on the model, water quality, maintenance, installation, use, and repair history. Follow the selected unit's manual and compare its written warranty.

Can I run two showers at once with a tankless?

A tankless unit can provide continuous hot water as long as the home's simultaneous demand stays within the unit's rated capacity. It is not literally unlimited, because incoming-water temperature and simultaneous fixture flow determine how much hot water the unit can deliver.

Do I need a gas line upgrade for a tankless?

Often, yes. Tankless units fire at much higher BTU input than tank water heaters during use. A licensed plumber sizes the gas line as part of the install assessment.

Is a tankless or heat pump water heater better?

Both can be good choices. Fuel, peak hot-water demand, available space, electrical and gas capacity, venting, water quality, installation cost, and current incentives determine the better fit.