DoesTheMath

A. O. SMITH HPACO-45 1**+AXST-66 1** vs LG APHWC501M: which uses less energy?

At the high draw pattern the LG APHWC501M uses 1,262 kWh a year and the A. O. SMITH HPACO-45 1**+AXST-66 1** 1,341 — 78 kWh (6%) less, about 785 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 high draw pattern.

Filed and computed figures
A. O. SMITH HPACO-45 1**+AXST-66 1** LG APHWC501M
UEF (Uniform Energy Factor) 3.7 3.93 (better)
Energy use per year (kWh) 1,341 1,262 (better)
First hour rating (gal) 82 76
Rated storage volume (gal) 60 53
Installed cost range $3,505–$4,492 $3,304–$4,656
ENERGY STAR certified yes yes
Refrigerant R-744 (CO2), GWP 1 R-134a, GWP 1430
On the market since 2026-02-13 2024-03-01
DOE CCD · 2026-09-19

What it costs to run

A. O. SMITH HPACO-45 1**+AXST-66 1**: 1,341 kWh a year LG APHWC501M: 1,262 kWh a year

A. O. SMITH HPACO-45 1**+AXST-66 1** — 1,341 kWh a year LG APHWC501M — 1,262 kWh a year

LG APHWC501M is 79 kWh a year lower than A. O. SMITH HPACO-45 1**+AXST-66 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.
  • 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-66 1** since 2026-02-13, the LG APHWC501M since 2024-03-01. A sale date, not a lifespan.

Which should you pick?

  • Pick the LG APHWC501M if running cost matters most: it uses 78 kWh less a year on the same test.
  • Pick the A. O. SMITH HPACO-45 1**+AXST-66 1** if you need more hot water in your busiest hour: it lists a first hour rating of 82 gallons against 76.
  • Neither if your household's busiest hour needs more than 82 gallons of hot water — neither lists more. Check whether a 50-gallon heater is enough.

Each model on its own

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