Rinnai CX199I vs Rinnai RX199I
Two of the gas tankless water heaters in our best gas tankless water heaters comparison, lined up spec by spec. Every figure comes from the manufacturer pages linked below, and the scores use the same published formula as the full ranking.
Affiliate disclosure: We earn a commission if you buy through links on this page, at no extra cost to you. It never affects our rankings, which come from the published scoring formula. As an Amazon Associate I earn from qualifying purchases. Learn more.
Best for: Official UEF 0.98, maximum 5.8 GPM, minimum activation 0.1 GPM
Check price at AmazonBest for: Official UEF 0.98, maximum 5.8 GPM, minimum activation 0.1 GPM
Check price at AmazonSpec-by-spec comparison
Green marks the better published figure. "Not listed" means the manufacturer doesn't publish it.
| Spec | Rinnai CX199I | Rinnai RX199I | Weight |
|---|---|---|---|
| Uniform energy factorOfficial ENERGY STAR uniform energy factor. Higher means more hot water delivered per unit of fuel. Missing values take the category minimum. | 0.98 | 0.98 | 34% |
| Maximum flowOfficial ENERGY STAR maximum gallons per minute. This is a lab rating, not a guarantee at your incoming water temperature. Missing values take the category minimum. | 5.8 GPM | 5.8 GPM | 32% |
| Minimum activation flowOfficial ENERGY STAR minimum gallons per minute needed to start the heater. Lower is better for low-flow fixtures. Missing values take the category minimum (the highest minimum flow in the set). | 0.1 GPM | 0.1 GPM | 18% |
| Connected capableYes when the official ENERGY STAR record lists the model as connected-capable. Unstated counts as no. | No | No | 16% |
| Uniform energy factor (ENERGY STAR UEF) | 0.98 | 0.98 | info |
| Maximum flow (ENERGY STAR) | 5.8 GPM | 5.8 GPM | info |
| Minimum activation flow (ENERGY STAR) | 0.1 GPM | 0.1 GPM | info |
| Fuel (ENERGY STAR) | Natural Gas, Propane | Natural Gas, Propane | info |
| Vent type (ENERGY STAR) | Power Direct Vent | Power Direct Vent | info |
| Input rate (ENERGY STAR) | 199,000 BTU/h | 199,000 BTU/h | info |
| Annual natural-gas use (ENERGY STAR) | 173 therms/year | 173 therms/year | info |
| Maximum GPM per 10,000 BTU/h (computed) | 0.29 GPM per 10,000 BTU/h, computed as certified maximum GPM ÷ certified input rate | 0.29 GPM per 10,000 BTU/h, computed as certified maximum GPM ÷ certified input rate | info |
| Connected capable (ENERGY STAR) | No | No | info |
| Draw pattern (ENERGY STAR) | High-Usage | High-Usage | info |
| Recovery efficiency (ENERGY STAR) | 99% | 99% | info |
| Dimensions (ENERGY STAR) | 25.8 × 18.5 × 11.4 in (H × W × D) | 25.8 × 18.5 × 11.4 in (H × W × D) | info |
| Certified model number | (CX199I) REU-NB3237FFC-US | (RX199I) REU-NB3237FF-US | info |
| Official brand name on the ENERGY STAR record | Rinnai | Rinnai | info |
| HeatPick score | 8.1/10 | 8.1/10 | 100% |
Where each one comes out ahead
Rinnai CX199I
No scored spec where it is strictly ahead; its case rests on the strengths below.
What we like
- Highest official uniform energy factor in this comparison (0.98)
- High official maximum flow (5.8 GPM)
- Lowest official minimum activation flow in this comparison (0.1 GPM)
Watch out for
- ENERGY STAR does not list this model as connected-capable
Rinnai RX199I
No scored spec where it is strictly ahead; its case rests on the strengths below.
What we like
- Highest official uniform energy factor in this comparison (0.98)
- High official maximum flow (5.8 GPM)
- Lowest official minimum activation flow in this comparison (0.1 GPM)
Watch out for
- ENERGY STAR does not list this model as connected-capable
Verdict
Two official Rinnai 199,000 BTU/h-class records. The CX199I record lists a 0.98 UEF, 5.8 GPM maximum flow and 0.1 GPM minimum activation flow. The RX199I record lists the same official UEF, maximum flow and minimum activation flow. ENERGY STAR does not list either as connected-capable. The certified model numbers differ (REU-NB3237FFC-US on the CX199I and REU-NB3237FF-US on the RX199I). We do not infer a recirculation or other hardware difference from the letters alone, because those features are not in the ENERGY STAR fields we used.
- Rinnai CX199I: ENERGY STAR Product Finder: CX199I
- Rinnai CX199I: ENERGY STAR certified water heaters dataset
- Rinnai RX199I: ENERGY STAR Product Finder: RX199I
- Rinnai RX199I: ENERGY STAR certified water heaters dataset