Navien NPE-180S2 vs Rinnai CX199I REU-NB3237FFC-US
The Rinnai CX199I REU-NB3237FFC-US is the more efficient unit: UEF 0.98 versus 0.96 — about 2% less energy for the same hot water. At national average rates that works out to about $251/year for the Rinnai CX199I REU-NB3237FFC-US against $255/year for the Navien NPE-180S2 — a $4 annual difference. The Rinnai CX199I REU-NB3237FFC-US sustains the higher flow (5.8 GPM vs 4.4 GPM under the DOE test).
| Navien NPE-180S2 | Rinnai CX199I REU-NB3237FFC-US | |
|---|---|---|
| Uniform Energy Factor (UEF) | 0.96 | 0.98 |
| Fuel | Natural Gas, Propane | Natural Gas, Propane |
| Max flow rate | 4.4 GPM | 5.8 GPM |
| Draw pattern | High | High |
| Annual gas use (natural gas) | 176 therms/yr | 173 therms/yr |
| Gas input rate | 150 kBTU/h | 199 kBTU/h |
| Max current draw | 5 A | 4 A |
| Vent type | Power Direct Vent | Power Direct Vent |
| Recovery efficiency | — | 99 % |
| Smart / connected capable | No | No |
| Minimum activation flow | 1 GPM | 0.1 GPM |
| Annual propane use | 192.35 gal/yr | 189.07 gal/yr |
| Vent size | 2 | 2 |
| Height | 27 in | 25.8 in |
| Diameter | — | 11.4 in |
| Width | 17 in | 18.5 in |
| Depth | 13 in | 11.4 in |
| ENERGY STAR certified | Yes | Yes |
Frequently asked questions
Which costs less to run, the Navien NPE-180S2 or the Rinnai CX199I REU-NB3237FFC-US?
The Rinnai CX199I REU-NB3237FFC-US: about $251/year versus $255/year for the Navien NPE-180S2 at national average rates — a $4 annual difference.
Are the Navien NPE-180S2 and Rinnai CX199I REU-NB3237FFC-US both ENERGY STAR certified?
Yes — every water heater in this database is drawn from the U.S. EPA ENERGY STAR certified water heater datasets.