Friedrich FDTGH-S11I is a gas tankless water heater from Friedrich rated 5.8 GPM at a 0.96 UEF — 176 therms/yr certified use, 199k BTU/h input.
Our take
The 199 kBTU sibling of Friedrich's well-specced tankless line hits the class median or better everywhere: 0.96 UEF (93rd percentile, about $255 a year on natural gas), 98% recovery efficiency, 5.8 GPM rated with ~5.5 GPM sustained at a cold-climate rise, and a sensitive 0.4 GPM activation flow. Plain direct venting over 2-inch pipe keeps the flue simple. Ten catalog listings across 3 brand names — Friedrich, Rheem, Ruud — are this same certified hardware, so the cheapest badge is the rational buy. Dual-fuel certified.
Best for: Low-activation whole-house duty on either fuel.
Trade-off: Ties rather than leads the class — the 0.98-UEF units run ~$4/yr cheaper.
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 Friedrich FDTGH-S11I at common temperature
rises (a typical shower uses about 2 GPM of mixed water):
The Friedrich FDTGH-S11I is certified hardware that Friedrich and its partner brands
publish under 10 names. The same specifications apply to every
variant:
Is the Friedrich FDTGH-S11I ENERGY STAR certified?
Yes, the Friedrich FDTGH-S11I holds a current ENERGY STAR certification for water heating efficiency (UEF 0.96).
How much does the Friedrich FDTGH-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 Friedrich FDTGH-S11I use?
The Friedrich FDTGH-S11I uses Direct Vent venting with 2 in vent connections. Matching the existing vent type is usually the cheapest replacement path.
Is the Friedrich FDTGH-S11I a smart water heater?
No, the Friedrich FDTGH-S11I is not connected-capable — it has no app connectivity or demand-response support.
