DoesTheMath

EEMAX ECO POU 3.5 vs Westinghouse ET003: which uses less energy?

At the very small draw pattern the EEMAX ECO POU 3.5 uses 622 kWh a year and the Westinghouse ET003 635 — 13 kWh (2%) less, about 134 kWh over ten years. Both are filed as an electric 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 an electric tankless unit at the very small draw pattern.

Filed and computed figures
Figure EEMAX ECO POU 3.5 Westinghouse ET003
UEF (Uniform Energy Factor) 0.95 (better) 0.93
Energy use per year (kWh) 622 (better) 635
Max flow (GPM) 0.3 0.3
Installed cost range $1,303–$1,814 $1,297–$1,766
ENERGY STAR certified not matched not matched
DOE CCD · 2026-09-19

What it costs to run

EEMAX ECO POU 3.5: 622 kWh a year Westinghouse ET003: 635 kWh a year

EEMAX ECO POU 3.5 — 622 kWh a year Westinghouse ET003 — 635 kWh a year

EEMAX ECO POU 3.5 is 13 kWh a year lower than Westinghouse ET003.

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 EEMAX ECO POU 3.5 if running cost matters most: it uses 13 kWh less a year on the same test.
  • Pick the Westinghouse ET003 if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the EEMAX ECO POU 3.5.
  • Neither if you need more than 0.3 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.

Each model on its own