Rinnai RX199I REU-NB3237FF-US
Rinnai RX199I REU-NB3237FF-US is a gas tankless water heater from Rinnai rated 5.8 GPM at a 0.98 UEF.
| Uniform Energy Factor (UEF) | 0.98 |
|---|---|
| Annual gas use (natural gas) | 173 therms/yr |
| Recovery efficiency | 99 % |
| Annual propane use | 189.07 gal/yr |
| Fuel | Natural Gas, Propane |
|---|
| Max flow rate | 5.8 GPM |
|---|---|
| Draw pattern | High |
| Minimum activation flow | 0.1 GPM |
| Gas input rate | 199 kBTU/h |
|---|
| Max current draw | 4 A |
|---|---|
| Vent type | Power Direct Vent |
| Vent size | 2 |
| Smart / connected capable | No |
|---|
| Height | 25.8 in |
|---|---|
| Diameter | 11.4 in |
| Width | 18.5 in |
| Depth | 11.4 in |
| ENERGY STAR certified | Yes |
|---|
Real flow rate by climate
A tankless heater's usable flow depends on how far it must raise incoming water temperature. Sustained hot-water flow of the Rinnai RX199I REU-NB3237FF-US at common temperature rises (a typical shower uses about 2 GPM of mixed water):
| Temperature rise | Climate | Sustained flow | Simultaneous showers |
|---|---|---|---|
| 45 °F | Warm climate (~75 °F groundwater) | 5.8 GPM | 2 |
| 55 °F | Mild climate (~65 °F groundwater) | 5.8 GPM | 2 |
| 70 °F | Cold climate (~50 °F groundwater) | 5.6 GPM | 2 |
| 77 °F | DOE test condition | 5.1 GPM | 2 |
Similar water heaters
- A. O. Smith ACTH-199M-(N,P) 1 (UEF 0.95)
- A. O. Smith T-H3-OS-N 1 (ACT-199O-N 1) (UEF 0.95)
- A. O. Smith T-H3-OS-N 1 (ACT-199O-P 1-1) (UEF 0.95)
- A. O. Smith T-H3-OS-N 1 (ATO-540H 1) (UEF 0.95)
- A. O. Smith T-H3-OS-N 1 (ATO-540H 1-1) (UEF 0.95)
- A. O. Smith T-H3-OS-N 1 (ATO-540HX3-N 1) (UEF 0.95)
Frequently asked questions
Is the Rinnai RX199I REU-NB3237FF-US ENERGY STAR certified?
Yes, the Rinnai RX199I REU-NB3237FF-US holds a current ENERGY STAR certification for water heating efficiency (UEF 0.98).
How much does the Rinnai RX199I REU-NB3237FF-US cost to run per year?
About $251 per year at national average energy rates, based on its certified annual energy use under the DOE test draw pattern. Your rate and usage change this figure.
What venting does the Rinnai RX199I REU-NB3237FF-US use?
The Rinnai RX199I REU-NB3237FF-US uses Power Direct Vent venting with 2 in vent connections. Matching the existing vent type is usually the cheapest replacement path.
Is the Rinnai RX199I REU-NB3237FF-US a smart water heater?
No, the Rinnai RX199I REU-NB3237FF-US is not connected-capable — it has no app connectivity or demand-response support.
Sources
- data.energystar.gov (retrieved 2026-07-17)