DoesTheMath

AMERICAN STANDARD WATER HEATERS ENS50L-* vs ARISTON ENS40LUB*: which uses less energy?

At the low draw pattern the AMERICAN STANDARD WATER HEATERS ENS50L-* uses 2,362 kWh a year and the ARISTON ENS40LUB* 2,439 — 77 kWh (3%) less, about 770 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
AMERICAN STANDARD WATER HEATERS ENS50L-* ARISTON ENS40LUB*
UEF (Uniform Energy Factor) 0.95 (better) 0.92
Energy use per year (kWh) 2,362 (better) 2,439
First hour rating (gal) 55 50
Rated storage volume (gal) 41 36
Installed cost range $1,683–$2,577 $1,591–$1,802
ENERGY STAR certified not matched not matched
DOE CCD · 2026-09-19

What it costs to run

AMERICAN STANDARD WATER HEATERS ENS50L-*: 2,362 kWh a year ARISTON ENS40LUB*: 2,439 kWh a year

AMERICAN STANDARD WATER HEATERS ENS50L-* — 2,362 kWh a year ARISTON ENS40LUB* — 2,439 kWh a year

AMERICAN STANDARD WATER HEATERS ENS50L-* is 77 kWh a year lower than ARISTON ENS40LUB*.

DOE CCD · 2026-09-19

Report an issue with this number

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 AMERICAN STANDARD WATER HEATERS ENS50L-* if running cost matters most: it uses 77 kWh less a year on the same test.
  • Pick the ARISTON ENS40LUB* if the installed price matters more than the running cost: its modeled installed range is $1,591–$1,802 against $1,683–$2,577.
  • Neither if your household's busiest hour needs more than 55 gallons of hot water — neither lists more. Check whether a 40-gallon heater is enough.

Each model on its own

Analytics cookies

We count page views without cookies for everyone, and that counter is what we use to decide what to build. Google Analytics is separate: it uses cookies to record how a page was used, and it loads only if you allow it. Decline and the site works exactly the same. What we collect.