DoesTheMath

A. O. SMITH ENS-40W 1** vs Ruud MSR50245 C: which uses less energy?

At the low draw pattern the Ruud MSR50245 C uses 2,494 kWh a year and the A. O. SMITH ENS-40W 1** 2,550 — 57 kWh (2%) less, about 567 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 ENS-40W 1** Ruud MSR50245 C
UEF (Uniform Energy Factor) 0.88 0.9 (better)
Energy use per year (kWh) 2,550 2,494 (better)
First hour rating (gal) 41 41
Rated storage volume (gal) 37 48
Installed cost range not published not published
ENERGY STAR certified not matched not matched
DOE CCD · 2026-09-19

What it costs to run

A. O. SMITH ENS-40W 1**: 2,550 kWh a year Ruud MSR50245 C: 2,494 kWh a year

A. O. SMITH ENS-40W 1** — 2,550 kWh a year Ruud MSR50245 C — 2,494 kWh a year

Ruud MSR50245 C is 56 kWh a year lower than A. O. SMITH ENS-40W 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 Ruud MSR50245 C if running cost matters most: it uses 57 kWh less a year on the same test.
  • Pick the A. O. SMITH ENS-40W 1** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the Ruud MSR50245 C.
  • Neither if your household's busiest hour needs more than 41 gallons of hot water — neither lists more. Check whether a 50-gallon heater is enough.

Each model on its own

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