A. O. SMITH T-H3S-OS-N 1** vs Ruud SFT 199-1: which uses less energy?
At the high draw pattern the A. O. SMITH T-H3S-OS-N 1** uses 180 therms a year and the Ruud SFT 199-1 188 — 8 therms (4%) less, about 80 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 high draw pattern.
| Figure | A. O. SMITH T-H3S-OS-N 1** | Ruud SFT 199-1 |
|---|---|---|
| UEF (Uniform Energy Factor) | 0.94 (better) | 0.9 |
| Energy use per year (therms) | 180 (better) | 188 |
| Max flow (GPM) | 5.3 | 5.3 |
| Installed cost range | $2,311–$3,350 | $2,122–$3,129 |
| 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 A. O. SMITH T-H3S-OS-N 1** if running cost matters most: it uses 8 therms less a year on the same test.
- Pick the Ruud SFT 199-1 if the installed price matters more than the running cost: its modeled installed range is $2,122–$3,129 against $2,311–$3,350.
- Neither if you need more than 5.3 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 T-H3S-OS-N 1**
Its filed figures, class position and running cost on your ZIP.
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Ruud SFT 199-1
Its filed figures, class position and running cost on your ZIP.