DoesTheMath

EEMAX SPEX4208 vs Stiebel Eltron Mini-E 3.5-1: which uses less energy?

At the very small draw pattern the EEMAX SPEX4208 uses 609 kWh a year and the Stiebel Eltron Mini-E 3.5-1 615 — 6 kWh (1%) less, about 63 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
EEMAX SPEX4208 Stiebel Eltron Mini-E 3.5-1
UEF (Uniform Energy Factor) 0.97 (better) 0.96
Energy use per year (kWh) 609 (better) 615
Max flow (GPM) 0.4 0.4
Installed cost range $1,309–$1,862 $1,306–$1,838
ENERGY STAR certified not matched not matched
DOE CCD · 2026-09-19

What it costs to run

EEMAX SPEX4208: 609 kWh a year Stiebel Eltron Mini-E 3.5-1: 615 kWh a year

EEMAX SPEX4208 — 609 kWh a year Stiebel Eltron Mini-E 3.5-1 — 615 kWh a year

EEMAX SPEX4208 is 6 kWh a year lower than Stiebel Eltron Mini-E 3.5-1.

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 SPEX4208 if running cost matters most: it uses 6 kWh less a year on the same test.
  • Pick the Stiebel Eltron Mini-E 3.5-1 if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the EEMAX SPEX4208.
  • Neither if you need more than 0.4 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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