Condensing vs Non Condensing Tankless Water Heater: Full Comparison

When selecting an energy-efficient tankless water heater, homeowners face an important decision between condensing and non-condensing models. While both eliminate bulk storage tanks heating water continually, condensing heaters recover extra warmth from exhaust gases using an additional heat exchanger.

Weighing efficiency gains against higher condensing unit costs informs investments, saving energy and cutting bills long-term. This guide compares critical performance factors to help determine the optimal system that matches household needs and budgets.

What is a Tankless Water Heater?

A tankless water heater delivers hot water on demand without needing to store pre-heated water in a tank. Tankless systems heat water only as it flows through heating elements or burners in compact units mounted on walls. This on-demand design conserves energy since no standby heat gets wasted verses traditional tank heaters.

What is a Condensing Tankless Water Heater?

A condensing tankless water heater represents the most energy-efficient design thanks to an extra internal heat exchanger that recovers additional heat from expelled exhaust gases. This recovered thermal energy preheats incoming cold water, so the main heating elements don’t work as hard. Condensing technology can achieve 98% efficiency ratings for maximum energy savings.

What is a Non-Condensing Tankless Water Heater?

Non-condensing tankless water heaters lack secondary exhaust gas heat exchangers, so they cannot reclaim extra heat energy being lost through ventilation. But they still heat water on demand without bulky storage tanks. While not as efficient as condensing units, non-condensing tankless models cost less upfront and remain simpler in design.

How Condensing Tankless Operation Differs

Condensing tankless heaters extract additional thermal energy from expelled exhaust gases, which standard-vented non-condensing types of waste by losing outflow directly outside. This extra-efficient condenser connects a secondary stainless heat exchanger, transferring exhaust warmth into incoming cold water and preheating it slightly before the main heating elements activate.

Some condensing models claim up to 98% efficiency ratings thanks to this dual exhaust heat capture process. However, their advanced internal components do add purchase and professional installation costs. Evaluate projected energy savings against initial price investments below.

Energy Efficiency and Cost Differences

With exhaust warmth recovery transferring up to an extra 8–10 degrees into cold water preheating alone, condensing models conservatively save around 20–30% over non-condensing tankless units costing the same otherwise. These percentages translate into over $100 annually conserved for average homes.

Factor regional energy rates and existing heat source comparisons like gas prices replacing electric tanks to confirm actual savings expectations. Condensing tankless water heaters shine brightest in northern climates using high-efficiency gas heating, meeting thermal demands. Paybacks are slow in temperate southern zones lacking substantial climate differentials.

Longevity and Durability Considerations

Well-installed premium condensing tankless water heaters last 20–25 years, thanks to stainless components enduring hot exhaust gases with minimal corrosion or failures in their secondary heat exchangers relative to non-condensing copper heat sinks degrading faster.

Non-condensing units average lifespans of around 15-20 years, however, when maintained. Weigh longer-term reliability expectations against any installation price differences in your area.

Flow Rate Performance Factors

With additional heat-transferring components condensing recaptured warmth, maximum flow rates for condensing tankless models tend to measure around 8–11 GPM versus some non-condensing types exceeding 11 GPM outfitted with more heating elements directly instead of pre-heating subsystems.

Evaluate peak showering or simultaneous sink demands dropping flow pressures in your specific home to determine adequate GPM ratings before purchase. Know your limits.

Installation and Venting Considerations

Due to stainless flue requirements for safely venting acidic exhaust gases externally, condensing tankless water heater installations cost $300+ on average greater than non-condensing models simply connecting standard plastic Category 3 vents directly through walls instead.

Weigh hiring professional installers who meet manufacturer specifications against DIY capabilities too. Getting condensing venting positions wrong risks dangerous flue gases entering homes. Don’t cut corners; use qualified technicians.

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Verdict: Are Condensing Upgrades Worth Costs?

In northern zones lacking natural gas lines where electricity costs exceed 12 cents per kWh, condensing tankless water heaters make excellent financial sense, recouping upgrades within 5 years on average thanks to their 20–40% heating efficiency improvements that convert fuel into hot water instead of waste gases.

Regions with lower energy costs may balance reliability gains against moderating fuel inflation and better-sustaining household budgets in the long run. Evaluate both initial price investment tradeoffs against projected energy savings specific to your situation. When unsure, contact installers directly, seeking professional payback guidance. Thorough data cuts guesswork.


Can you install condensing tankless models outdoors?

Yes. Condensing tankless water heaters prove ideal for outdoor installations. Actually, thanks to their reliance on stainless exhaust venting, they built enduring temperature swings without failures, cracking plastic pipes prone indoors. Just ensure adequate freeze protection.

Do condensing tankless heaters need bigger gas lines?

Sometimes. Their higher BTU heating capacities demand around 150-200kBtu gas connections over 100-150kBtu non-condensing units. Consult sizing guides factoring households needing bursts above 20+ GPM flows to determine infrastructure requirements before installing either system type upgrading flows.

Which is easier to maintain long-term?
While both last over 15 years with basic flush cleansing, condensing tankless water heaters demand professional servicing, ensuring secondary heat exchanger integrity and optimizing efficiency and lifespans, according to manufacturers. Expect moderate annual upkeep fees. DIY non-condensing units, if handy capable of self-flushing instead.