DoesTheMath

A. O. SMITH HESF-40 1** vs ARISTON ARIHPWH-40-T: which uses less energy?

At the medium draw pattern the ARISTON ARIHPWH-40-T uses 915 kWh a year and the A. O. SMITH HESF-40 1** 3,531 — 2,616 kWh (74%) less, about 26,157 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 medium draw pattern.

Filed and computed figures
A. O. SMITH HESF-40 1** ARISTON ARIHPWH-40-T
UEF (Uniform Energy Factor) 0.92 3.55 (better)
Energy use per year (kWh) 3,531 915 (better)
First hour rating (gal) 64 65
Rated storage volume (gal) 37 37
Installed cost range $1,605–$1,828 not published
ENERGY STAR certified not matched yes
Refrigerant not filed R-513A, GWP 630
On the market since not filed 2025-09-01
DOE CCD · 2026-09-19

What it costs to run

A. O. SMITH HESF-40 1**: 3,531 kWh a year ARISTON ARIHPWH-40-T: 915 kWh a year

A. O. SMITH HESF-40 1** — 3,531 kWh a year ARISTON ARIHPWH-40-T — 915 kWh a year

ARISTON ARIHPWH-40-T is 2,616 kWh a year lower than A. O. SMITH HESF-40 1**.

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

Which should you pick?

  • Pick the ARISTON ARIHPWH-40-T if running cost matters most: it uses 2,616 kWh less a year on the same test.
  • Pick the A. O. SMITH HESF-40 1** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the ARISTON ARIHPWH-40-T.
  • Neither if your household's busiest hour needs more than 65 gallons of hot water — neither lists more. Check whether a 40-gallon heater is enough.

Each model on its own

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