DoesTheMath

ARISTON ARIHPWH-40-T vs RELIANCE WATER HEATERS PESX-40 1**: which uses less energy?

At the medium draw pattern the ARISTON ARIHPWH-40-T uses 915 kWh a year and the RELIANCE WATER HEATERS PESX-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
ARISTON ARIHPWH-40-T RELIANCE WATER HEATERS PESX-40 1**
UEF (Uniform Energy Factor) 3.55 (better) 0.92
Energy use per year (kWh) 915 (better) 3,531
First hour rating (gal) 65 66
Rated storage volume (gal) 37 37
Installed cost range not published $1,605–$1,828
ENERGY STAR certified yes not matched
Refrigerant R-513A, GWP 630 not filed
On the market since 2025-09-01 not filed
DOE CCD · 2026-09-19

What it costs to run

ARISTON ARIHPWH-40-T: 915 kWh a year RELIANCE WATER HEATERS PESX-40 1**: 3,531 kWh a year

ARISTON ARIHPWH-40-T — 915 kWh a year RELIANCE WATER HEATERS PESX-40 1** — 3,531 kWh a year

ARISTON ARIHPWH-40-T is 2,616 kWh a year lower than RELIANCE WATER HEATERS PESX-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 RELIANCE WATER HEATERS PESX-40 1** if you need more hot water in your busiest hour: it lists a first hour rating of 66 gallons against 65.
  • Neither if your household's busiest hour needs more than 66 gallons of hot water — neither lists more. Check whether a 40-gallon heater is enough.

Each model on its own

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