DoesTheMath

A. O. SMITH MHE6-40RW-035D-1** vs ARISTON ENS40LUB 240V-3500W: which uses less energy?

At the low draw pattern the ARISTON ENS40LUB 240V-3500W uses 2,439 kWh a year and the A. O. SMITH MHE6-40RW-035D-1** 2,466 — 27 kWh (1%) less, about 268 kWh over ten years. Both are filed as an electric tank, 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 tank at the low draw pattern.

Filed and computed figures
A. O. SMITH MHE6-40RW-035D-1** ARISTON ENS40LUB 240V-3500W
UEF (Uniform Energy Factor) 0.91 0.92 (better)
Energy use per year (kWh) 2,466 2,439 (better)
First hour rating (gal) 40 39
Rated storage volume (gal) 36 36
Installed cost range not published $1,591–$1,802
ENERGY STAR certified not matched not matched
DOE CCD · 2026-09-19

What it costs to run

A. O. SMITH MHE6-40RW-035D-1**: 2,466 kWh a year ARISTON ENS40LUB 240V-3500W: 2,439 kWh a year

A. O. SMITH MHE6-40RW-035D-1** — 2,466 kWh a year ARISTON ENS40LUB 240V-3500W — 2,439 kWh a year

ARISTON ENS40LUB 240V-3500W is 27 kWh a year lower than A. O. SMITH MHE6-40RW-035D-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 ARISTON ENS40LUB 240V-3500W if running cost matters most: it uses 27 kWh less a year on the same test.
  • Pick the A. O. SMITH MHE6-40RW-035D-1** if you need more hot water in your busiest hour: it lists a first hour rating of 40 gallons against 39.
  • Neither if your household's busiest hour needs more than 40 gallons of hot water — neither lists more. Check whether a 40-gallon heater is enough.

Each model on its own

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