DoesTheMath

A. O. SMITH HPTU-50N 1** vs LOCHINVAR HPACO-45 1**+AXST-50T 1**: which uses less energy?

At the medium draw pattern the LOCHINVAR HPACO-45 1**+AXST-50T 1** uses 923 kWh a year and the A. O. SMITH HPTU-50N 1** 942 — 19 kWh (2%) less, about 187 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 HPTU-50N 1** LOCHINVAR HPACO-45 1**+AXST-50T 1**
UEF (Uniform Energy Factor) 3.45 3.52 (better)
Energy use per year (kWh) 942 923 (better)
First hour rating (gal) 66 67
Rated storage volume (gal) 46 45
Installed cost range $3,022–$4,110 $2,998–$4,170
ENERGY STAR certified yes yes
Refrigerant R-134a, GWP 1430 R-744 (CO2), GWP 1
On the market since 2019-04-05 2026-02-13
DOE CCD · 2026-09-19

What it costs to run

A. O. SMITH HPTU-50N 1**: 942 kWh a year LOCHINVAR HPACO-45 1**+AXST-50T 1**: 923 kWh a year

A. O. SMITH HPTU-50N 1** — 942 kWh a year LOCHINVAR HPACO-45 1**+AXST-50T 1** — 923 kWh a year

LOCHINVAR HPACO-45 1**+AXST-50T 1** is 19 kWh a year lower than A. O. SMITH HPTU-50N 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 HPTU-50N 1** since 2019-04-05, the LOCHINVAR HPACO-45 1**+AXST-50T 1** since 2026-02-13. A sale date, not a lifespan.

Which should you pick?

  • Pick the LOCHINVAR HPACO-45 1**+AXST-50T 1** if running cost matters most: it uses 19 kWh less a year on the same test.
  • Pick the A. O. SMITH HPTU-50N 1** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the LOCHINVAR HPACO-45 1**+AXST-50T 1**.
  • Neither if your household's busiest hour needs more than 67 gallons of hot water — neither lists more. Check whether a 40-gallon heater is enough.

Each model on its own

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