Demand Duo presents the best of tank and tankless water heaters

Demand Duo™ Hybrid Commercial Water Heating System

Get the Best of Both with Rinnai’s Demand Duo™ 

Rinnai’s Demand Duo™ Commercial Hybrid Water Heating System is the smart choice when it’s time to replace a standard tank. Featuring a part-tank, part-tankless design, the Demand Duo offers the best of both technologies in a quick and easy upgrade that delivers an endless supply of hot water.

The Rinnai Demand Duo pairs a durable, energy-efficient 119-gallon storage tank with a Rinnai C199 tankless unit, creating a direct replacement solution with connections similar to most high-efficiency tanks that provides continuous hot water. This means the Demand Duo is simple to install and keeps pace with an establishment’s hot water needs – from brief, high-spike draws to a supply that is ready to go the distance, day in and day out. 

Greater Capacity + Longer Lifespan

Because the Demand Duo’s heat source is placed outside the tank, it actually offers more water heating capacity than traditional units. Furthermore, the removal of the heating element from inside the tank eliminates thermal stress on the tank itself, lengthening the life of the unit and its ability to consistently output hot water. In fact, Rinnai’s warranty on the Demand Duo is twice that of traditional commercial tanks (6-year heat exchanger and tank, 5-year parts, 2-year labor), and it is backed with a No Risk Satisfaction Guarantee.*

Key Features: 

  • Built standard with 199,000 BTU C199 commercial tankless water heater
  • Ultra low NOx compliant
  • Commercial ENERGY STAR® certified
  • Multiple venting options (PVC/CPVC, Room Air, Concentric, Common Vent)
  • System weight up to 250 lbs. lighter than competitive units


Get the Best of Both Worlds


Demand Duo

Why Choose Rinnai® Demand Duo™ ?

  • Longer life vs. traditional tank
  • 2X the warranty
  • 6-year heat exchanger and tank/ 5-year parts/ 2-year labor
  • Saves money with less energy cost vs. standard- efficiency water heater
  • Performs better by combining best of tank and tankless technologies
  • Ease of repair – all parts are replaceable

View Models & Specifications (80 gallon storage tank) >

View Models & Specifications (100 gallon storage tank) >


Don’t Just Swap Out, Swap Up
Rinnai’s Demand Duo™ commercial hybrid heating system is the smart choice when it’s time to replace a standard tank. Our unique “best of both” system lets your business quickly and easily upgrade to a unit that offers an on-demand and continuous supply of hot water.


Why Choose Rinnai® Demand Duo™ 80-gallon ?


Introducing the newest member of the Demand Duo Family of Product. The Demand Duo 80-gallon.

Featuring a durable energy-efficient 80-gallon tank storage tank paired with a RL94 tankless unit

As the heat source, the RL94 tankless unit eliminates thermal stress on the tank, lengthening the life and maximizing the performance of the unit

Ideal for emergency replacement situations

Efficient tank recovery methods deliver consistent hot water even during re-heat cycles

Easy cost-effective maintenance with readily available parts