Navien NPE-180S2 vs Richmond RTGH-S84I: which uses less energy?
At the high draw pattern the Navien NPE-180S2 and the Richmond RTGH-S84I use the same energy, 176 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 | Navien NPE-180S2 | Richmond RTGH-S84I |
|---|---|---|
| UEF (Uniform Energy Factor) | 0.96 | 0.96 |
| Energy use per year (therms) | 176 | 176 |
| Max flow (GPM) | 4.4 | 4.6 |
| Installed cost range NLR REMDB | $2,405–$3,460 | $2,405–$3,460 |
| ENERGY STAR certified ENERGY STAR | yes | yes |
| On the market since ENERGY STAR | 2021-01-01 | 2024-09-01 |
| CPSC recall naming it CPSC | none on file | none on file |
DOE CCD · 2026-09-19 NLR REMDB · 2026-04-01 ENERGY STAR · 2026-09-19 CPSC · 2026-09-24
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 above.
- No CPSC recall on file names either model (list checked 2026-09-24).
- 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 Navien NPE-180S2 since 2021-01-01, the Richmond RTGH-S84I since 2024-09-01. A sale date, not a lifespan.
Which should you pick?
- Pick the Richmond RTGH-S84I if you run more fixtures at once: it lists 4.6 GPM against 4.4.
- Neither if you need more than 4.6 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.
Each model on its own
- Navien NPE-180S2 176 therms a year
- Richmond RTGH-S84I 176 therms a year