Rinnai RX180I REU-NB2934FF-US is a gas tankless water heater from Rinnai rated 5.3 GPM at a 0.98 UEF — 173 therms/yr certified use, 180k BTU/h input.
MSRP: $1,789
Our take
Three class-leading numbers converge in Rinnai's RX180I: a 0.98 UEF that ties the 180 kBTU cohort ceiling (about $251 a year on natural gas), a 0.1 GPM activation flow — the lowest in this entire tankless database, meaning even a trickle fires the burner — and an 11.4-inch depth that makes it the slimmest cabinet in the class. Sustained flow reaches 5.0 GPM at a 70 °F rise. Dual-fuel certified, power-direct vented over 2-inch pipe, 98% recovery efficiency. Rinnai badge only; no rebrands exist in the certified data.
Best for: The spec-sheet pick of the 180 kBTU class, full stop.
Trade-off: Nothing in the certified data — rivals compete on price, not numbers.
Efficiency
Uniform Energy Factor (UEF)
0.98
Annual gas use (natural gas)
173 therms/yr
Recovery efficiency
98 %
Annual propane use
189.07 gal/yr
General
Fuel
Natural Gas, Propane
Capacity
Max flow rate
5.3 GPM
Draw pattern
High
Minimum activation flow
0.1 GPM
Performance
Gas input rate
180 kBTU/h
Installation
Max current draw
4 A
Vent type
Power Direct Vent
Vent size
2
Smart features
Smart / connected capable
No
Dimensions
Height
25.8 in
Diameter
11.4 in
Width
18.5 in
Depth
11.4 in
Certification
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 RX180I REU-NB2934FF-US at common temperature
rises (a typical shower uses about 2 GPM of mixed water):
Is the Rinnai RX180I REU-NB2934FF-US ENERGY STAR certified?
Yes, the Rinnai RX180I REU-NB2934FF-US holds a current ENERGY STAR certification for water heating efficiency (UEF 0.98).
How much does the Rinnai RX180I REU-NB2934FF-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 RX180I REU-NB2934FF-US use?
The Rinnai RX180I REU-NB2934FF-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 RX180I REU-NB2934FF-US a smart water heater?
No, the Rinnai RX180I REU-NB2934FF-US is not connected-capable — it has no app connectivity or demand-response support.
