DoesTheMath

Fogatti FDG420IN-CS120-NG vs Westinghouse HW120: which uses less energy?

At the medium draw pattern the Westinghouse HW120 uses 132 therms a year and the Fogatti FDG420IN-CS120-NG 135 — 3 therms (2%) less, about 32 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 medium draw pattern.

Filed and computed figures
Figure Fogatti FDG420IN-CS120-NG Westinghouse HW120
UEF (Uniform Energy Factor) 0.82 0.84 (better)
Energy use per year (therms) 135 132 (better)
Max flow (GPM) 2.9 3
Installed cost range $1,745–$2,687 $1,839–$2,798
ENERGY STAR certified not matched not matched
DOE CCD · 2026-09-19

What it costs to run

Fogatti FDG420IN-CS120-NG: 135 therms a year Westinghouse HW120: 132 therms a year

Fogatti FDG420IN-CS120-NG — 135 therms a year Westinghouse HW120 — 132 therms a year

Westinghouse HW120 is 3 therms a year lower than Fogatti FDG420IN-CS120-NG.

DOE CCD · 2026-09-19

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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.
  • The actual warranty term is printed in each model’s documentation, not in any registry.

Which should you pick?

  • Pick the Westinghouse HW120 if running cost matters most: it uses 3 therms less a year on the same test.
  • Pick the Fogatti FDG420IN-CS120-NG if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the Westinghouse HW120.
  • Neither if you need more than 3 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.

Each model on its own