A. O. SMITH ATO-140B-N 1** vs THERMALUX NR662-OD-NG: which uses less energy?
At the medium draw pattern the THERMALUX NR662-OD-NG uses 135 therms a year and the A. O. SMITH ATO-140B-N 1** 137 — 2 therms (1%) less, about 17 therms over ten years. Both are filed as a gas tankless unit, so the comparison holds. Enter your ZIP below to price the difference.
Side by side
Compared within one class only: models filed as a gas tankless unit at the medium draw pattern.
| Figure | A. O. SMITH ATO-140B-N 1** | THERMALUX NR662-OD-NG |
|---|---|---|
| UEF (Uniform Energy Factor) | 0.81 | 0.82 (better) |
| Energy use per year (therms) | 137 | 135 (better) |
| Max flow (GPM) | 3.6 | 3.6 |
| Installed cost range | $1,698–$2,632 | $1,745–$2,687 |
| ENERGY STAR certified | not matched | not matched |
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.
- The actual warranty term is printed in each model’s documentation, not in any registry.
Which should you pick?
- Pick the THERMALUX NR662-OD-NG if running cost matters most: it uses 2 therms less a year on the same test.
- Pick the A. O. SMITH ATO-140B-N 1** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the THERMALUX NR662-OD-NG.
- Neither if you need more than 3.6 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.
Each model on its own
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A. O. SMITH ATO-140B-N 1**
Its filed figures, class position and running cost on your ZIP.
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THERMALUX NR662-OD-NG
Its filed figures, class position and running cost on your ZIP.