Rheem RTGH-S11I is a gas tankless water heater from Rheem rated 5.8 GPM at a 0.96 UEF — 176 therms/yr certified use, 199k BTU/h input.
Also sold as the Friedrich FDTGH-S11I. This model is the same certified
hardware as the Friedrich FDTGH-S11I, published under a
different brand — full details, comparisons, and pricing live on that page. The
certified figures below are identical.
Efficiency
Uniform Energy Factor (UEF)
0.96
Annual gas use (natural gas)
176 therms/yr
Recovery efficiency
98 %
Annual propane use
192.35 gal/yr
General
Fuel
Natural Gas, Propane
Capacity
Max flow rate
5.8 GPM
Draw pattern
High
Minimum activation flow
0.4 GPM
Performance
Gas input rate
199 kBTU/h
Installation
Max current draw
2 A
Vent type
Direct Vent
Vent size
2
Smart features
Smart / connected capable
No
Dimensions
Width
18.1 in
Depth
13.6 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 Rheem RTGH-S11I at common temperature
rises (a typical shower uses about 2 GPM of mixed water):
Yes, the Rheem RTGH-S11I holds a current ENERGY STAR certification for water heating efficiency (UEF 0.96).
How much does the Rheem RTGH-S11I cost to run per year?
About $255 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 Rheem RTGH-S11I use?
The Rheem RTGH-S11I uses Direct Vent venting with 2 in vent connections. Matching the existing vent type is usually the cheapest replacement path.
Is the Rheem RTGH-S11I a smart water heater?
No, the Rheem RTGH-S11I is not connected-capable — it has no app connectivity or demand-response support.
