DoesTheMath

A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1** vs AMERICAN HPACO-45 1**+AXST-50S 1**: which uses less energy?

At the medium draw pattern the A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1** uses 915 kWh a year and the AMERICAN HPACO-45 1**+AXST-50S 1** 923 — 8 kWh (1%) less, about 78 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 HPACO-45 1**+AXST-50LBTTP 1** AMERICAN HPACO-45 1**+AXST-50S 1**
UEF (Uniform Energy Factor) 3.55 (better) 3.52
Energy use per year (kWh) 915 (better) 923
First hour rating (gal) 72 70
Rated storage volume (gal) 48 46
Installed cost range $3,099–$4,228 $3,030–$4,180
ENERGY STAR certified yes yes
Refrigerant R-744 (CO2), GWP 1 R-744 (CO2), GWP 1
On the market since 2026-02-13 2026-02-13
DOE CCD · 2026-09-19

What it costs to run

A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1**: 915 kWh a year AMERICAN HPACO-45 1**+AXST-50S 1**: 923 kWh a year

A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1** — 915 kWh a year AMERICAN HPACO-45 1**+AXST-50S 1** — 923 kWh a year

A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1** is 8 kWh a year lower than AMERICAN HPACO-45 1**+AXST-50S 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.
  • Both are ENERGY STAR certified, which requires a manufacturer warranty of at least six years; the actual term for each model is not published.
  • Time on the market, as filed with ENERGY STAR: the A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1** since 2026-02-13, the AMERICAN HPACO-45 1**+AXST-50S 1** since 2026-02-13. A sale date, not a lifespan.

Which should you pick?

  • Pick the A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1** if running cost matters most: it uses 8 kWh less a year on the same test.
  • Pick the AMERICAN HPACO-45 1**+AXST-50S 1** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1**.
  • Neither if your household's busiest hour needs more than 72 gallons of hot water — neither lists more. Check whether a 50-gallon heater is enough.

Each model on its own

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