Navien NPE-240A Premium Condensing Tankless Water Heater (Legacy)

The Navien NPE-240A is Navien's flagship 199,000 BTU residential condensing tankless water heater, sized for households with 3+ bathrooms or significant overlapping hot-water demand. The defining feature is ComfortFlow — a built-in 0.5-gallon buffer tank plus an integrated recirculation pump — that addresses the two limitations of standard tankless: the cold-water sandwich at restart, and the wait-time for hot water to reach a distant tap.

Specs: 199,000 BTU input, UEF 0.93, full stainless steel dual heat exchanger (resists hard-water scaling), up to 11.2 GPM at a 35°F rise or 5.4 GPM at a 70°F rise. The full-stainless construction is Navien's distinguishing engineering choice versus Rinnai's mixed copper-and-stainless approach; tradeoffs are similar to the Rinnai RX series — slightly less thermally efficient but materially better hard-water tolerance.

The ComfortFlow buffer-and-recirc combination is the real differentiator at the install. With ComfortFlow active, the cold-water sandwich that plagues most tankless installs (cold burst when restarting flow within 30–60 seconds of stopping) becomes a 1–2 second blip rather than a 10–15 second cold flow. The integrated recirc pump can be programmed for time-of-day operation, on-demand activation via a button at the sink, or smart-pattern learning. The buffer eliminates the need for an external recirc system that would otherwise add $400–$1,200 to the install on retrofit projects.

Warranty: 15 years on the heat exchanger, 5 years on parts, 1 year on labor. Service network is smaller than Rinnai's but has been expanding rapidly since 2020. The right buyer is a household where the cold-water sandwich is the dealbreaker complaint — Navien solves that problem more comprehensively than any other major tankless brand. Installed cost typically $4,150 including the gas-line upsize and PVC venting.

This is the "Legacy" generation of the NPE-240A; Navien's newer NPE-2 series (NPE-240A2 and NPE-S2 variants) supersedes it in current production. The Legacy units remain widely available through wholesale channels and parts support is committed through 2032. Buying a Legacy unit today saves $200–$400 over the equivalent NPE-2 with identical performance for residential applications.