DoesTheMath

LAARS KGWH-150JFN vs NAVIEN NPE-180S2: which uses less energy?

At the high draw pattern the LAARS KGWH-150JFN uses 173 therms a year and the NAVIEN NPE-180S2 176 — 4 therms (2%) less, about 36 therms over ten years. Both are filed as a gas tankless unit, so the comparison holds. Enter your ZIP below to price the difference.

Side by side

Compared within one class only: models filed as a gas tankless unit at the high draw pattern.

Filed and computed figures
LAARS KGWH-150JFN NAVIEN NPE-180S2
UEF (Uniform Energy Factor) 0.98 (better) 0.96
Energy use per year (therms) 173 (better) 176
Max flow (GPM) 4.3 4.4
Installed cost range $2,499–$3,570 $2,405–$3,460
ENERGY STAR certified yes yes
Sound level (dB) 44 not filed
On the market since 2026-02-01 2021-01-01
DOE CCD · 2026-09-19

What it costs to run

LAARS KGWH-150JFN: 173 therms a year NAVIEN NPE-180S2: 176 therms a year

LAARS KGWH-150JFN — 173 therms a year NAVIEN NPE-180S2 — 176 therms a year

LAARS KGWH-150JFN is 3 therms a year lower than NAVIEN NPE-180S2.

DOE CCD · 2026-09-19

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Enter your ZIP to price both units on the same rate where you live.

Reliability

Not published: Reliability, failure rates and each model’s actual warranty term.

The registries these figures come from certify energy performance under a federal test; none of them records how long a unit lasts or how often it fails, so this page does not rank the two on reliability.

What is here instead:

  • The filed efficiency, capacity and tank size of both models, side by side below.
  • Both are ENERGY STAR certified, which requires a manufacturer warranty of at least six years; the actual term for each model is not published.
  • Time on the market, as filed with ENERGY STAR: the LAARS KGWH-150JFN since 2026-02-01, the NAVIEN NPE-180S2 since 2021-01-01. A sale date, not a lifespan.

Which should you pick?

  • Pick the LAARS KGWH-150JFN if running cost matters most: it uses 4 therms less a year on the same test.
  • Pick the NAVIEN NPE-180S2 if you run more fixtures at once: it lists 4.4 GPM against 4.3.
  • Neither if you need more than 4.4 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.

Each model on its own

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