Rheem IKONIC S11i

Last updated: October 31, 2026

Rheem IKONIC S11i
4.1/5#7 of 20 in gas tankless water heaters
4.1

A premium condensing heater for a large home that wants top efficiency and app control from one unit.

  • 199,900 BTU/hHeating power
  • 11.2 GPMMax flow
  • 0.96UEF
  • 15 yearsHeat exchanger warranty
Check price at Amazon$1,847.43Check price at Amazon$1,859.99

Price checked October 31, 2026. As an Amazon Associate we earn from qualifying purchases.

Pros
  • A 0.96 UEF is near the top of the class, so gas bills stay low
  • Built in Wi-Fi lets you set temperature and get alerts from a phone
  • Highest flow of the Rheem line for three or four showers at once
  • Field convertible between natural gas and propane
Cons
  • At 77.6 lb it is heavy to hang and may need extra wall support
  • Expensive next to non condensing whole home units
  • Amazon lists it with a lead time rather than in stock

How it scores

The rating comes from 4 measured or published factors, each scored 0-100 against fixed reference points for its fuel. How we rank explains each one.

Specifications

Model numberRECTGH-S11iN
Heating
FuelGas
Gas typeNatural gas or propane
Gas input11,000 to 199,900 BTU/h
Max flow11.2 GPM
UEF0.96
CondensingYes
ENERGY STARYes
Installation
VentingBoth
Vent type2 in or 3 in PVC/CPVC/PP
Weight77.6 lb
Features
Built-in recirculationNo
Wi-FiYes
Heat exchanger warranty15 years
Parts warranty5 years

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