GSW WATER HEATERS ATM-180M-N 1** vs JOHN WOOD ATHR-180M 1**: which uses less energy?
At the high draw pattern the GSW WATER HEATERS ATM-180M-N 1** and the JOHN WOOD ATHR-180M 1** use the same energy, 178 therms a year each, on the same federal test. Both are filed as a gas tankless unit, so the comparison holds; what separates them is below. Enter your ZIP to price either one on your own rate.
Side by side
Compared within one class only: models filed as a gas tankless unit at the high draw pattern.
| Figure | GSW WATER HEATERS ATM-180M-N 1** | JOHN WOOD ATHR-180M 1** |
|---|---|---|
| UEF (Uniform Energy Factor) | 0.95 | 0.95 |
| Energy use per year (therms) | 178 | 178 |
| Max flow (GPM) | 5.4 | 5.3 |
| Installed cost range | $2,358–$3,405 | $2,358–$3,405 |
| ENERGY STAR certified | yes | yes |
| On the market since | 2025-05-15 | 2024-02-01 |
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 GSW WATER HEATERS ATM-180M-N 1** since 2025-05-15, the JOHN WOOD ATHR-180M 1** since 2024-02-01. A sale date, not a lifespan.
Which should you pick?
- Pick the GSW WATER HEATERS ATM-180M-N 1** if its price or availability suits you — on energy the two are level.
- Pick the JOHN WOOD ATHR-180M 1** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the GSW WATER HEATERS ATM-180M-N 1**.
- Neither if you need more than 5.4 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.
Each model on its own
-
GSW WATER HEATERS ATM-180M-N 1**
Its filed figures, class position and running cost on your ZIP.
-
JOHN WOOD ATHR-180M 1**
Its filed figures, class position and running cost on your ZIP.