A. O. SMITH HPACO-45 1**+AXST-66 1** vs ECO-AIR HPWH - 65G: which uses less energy?
At the high draw pattern the ECO-AIR HPWH - 65G uses 1,272 kWh a year and the A. O. SMITH HPACO-45 1**+AXST-66 1** 1,341 — 69 kWh (5%) less, about 688 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.
| Figure | A. O. SMITH HPACO-45 1**+AXST-66 1** | ECO-AIR HPWH - 65G |
|---|---|---|
| UEF (Uniform Energy Factor) | 3.7 | 3.9 (better) |
| Energy use per year (kWh) | 1,341 | 1,272 (better) |
| First hour rating (gal) | 82 | 80 |
| Rated storage volume (gal) | 60 | 60 |
| Installed cost range | $3,505–$4,492 | $3,528–$4,692 |
| ENERGY STAR certified | yes | yes |
| Sound level (dB) | not filed | 49 |
| Refrigerant | R-744 (CO2), GWP 1 | R-134a, GWP 1430 |
| On the market since | 2026-02-13 | 2024-11-10 |
What it costs to run
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 ECO-AIR HPWH - 65G since 2024-11-10. A sale date, not a lifespan.
Which should you pick?
- Pick the ECO-AIR HPWH - 65G if running cost matters most: it uses 69 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 80.
- Neither if your household's busiest hour needs more than 82 gallons of hot water — neither lists more. Check whether a 65-gallon heater is enough.
Each model on its own
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A. O. SMITH HPACO-45 1**+AXST-66 1**
Its filed figures, class position and running cost on your ZIP.
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ECO-AIR HPWH - 65G
Its filed figures, class position and running cost on your ZIP.