Rheem IKONIC 8.4 GPM Natural Gas Tankless Water Heater Indoor
Rheem's top condensing indoor gas tankless -- 157,000 BTU, ultra-low NOx, and 0.96 UEF efficiency -- for buyers who want the highest-efficiency gas option regardless of install complexity.
Updated
- 0.96 UEF -- among the highest efficiency ratings in gas tankless
- 8.4 GPM flow rate at 157,000 BTU input
- Condensing design extracts heat from exhaust for maximum efficiency
- Ultra-low NOx certified for California and other regulated markets
Best For / Not For
Best for
- High-usage households where maximum efficiency justifies the install premium over a non-condensing unit
- Buyers in California and other low-NOx regulated markets where ultra-low NOx certification is required
- Homeowners who want indoor installation with the highest possible efficiency rating
Not for
- Buyers who want simplicity -- condensing venting and condensate drain add cost and complexity
- Most buyers comparing the IKONIC to the Rheem RTG outdoor -- the simpler non-condensing outdoor unit achieves the same GPM output with lower install cost
- Buyers without a location to route PVC vent pipes and a floor drain or condensate pump for drainage
Key Details
Condensing vs Non-Condensing: What It Means for Your Wallet
A condensing gas tankless heater recovers heat from the exhaust gases that a non-condensing unit exhausts to the atmosphere. That recovered heat pushes efficiency from roughly 80-82% in non-condensing units to 94-96% in condensing units. On paper, this looks like a significant efficiency gain. In practice, the math depends on how much gas you burn through and what gas costs in your area.
For a family of four using a tankless as a primary water heater, the annual gas cost difference between a 0.82 UEF and 0.96 UEF unit typically runs to a modest amount per year depending on local gas rates. The condensing installation adds cost upfront. Whether the payback period makes sense depends on your usage and how long you plan to stay in the home. For high-usage households or buyers making a long-term investment, the IKONIC's efficiency premium can justify the cost. For average users, the simpler Rheem RTG outdoor or Rinnai V53DeP provides equivalent hot water at lower total installation cost.
Installation Complexity Is the Real Decision Factor
Condensing units use PVC vent pipes instead of stainless steel, which is cheaper per linear foot -- but they also produce acidic condensate that must drain to a floor drain, utility sink, or condensate pump. In a finished basement or mechanical room without a floor drain nearby, adding condensate drainage can cost as much as the venting savings. Factor both into your install estimate before choosing the IKONIC over a non-condensing alternative.
If indoor installation is the priority and you have a suitable drain location, the IKONIC is a strong choice. If you have outdoor wall space and want to avoid the venting question entirely, the Rheem RTG outdoor achieves the same GPM output with simpler installation at a lower system cost. Choose based on your specific home, not on the efficiency spec alone.
Pros and Cons
Pros
- 0.96 UEF -- the highest efficiency tier in residential gas tankless
- Ultra-low NOx certification works in California and other restricted markets
- Condensing technology recovers heat that non-condensing units waste
- Indoor installation keeps the unit protected from weather
- Smart diagnostics and remote monitoring capable
Cons
- Condensing installation requires PVC venting and condensate drainage -- adds cost and complexity
- Higher purchase price than comparable non-condensing units with the same GPM output
- The efficiency gains over a non-condensing unit have a long payback period for most households
Bottom Line
Rheem IKONIC Indoor is a Consider. It is the right choice for high-usage households that need indoor installation and want the highest efficiency rating in the category. For most buyers, the Rheem RTG outdoor or Rinnai V53DeP achieves equivalent hot water output with lower installation complexity. Do the install-cost math before committing to the condensing route.
Check current price