The I- Series i090CN model features Rinnai's exclusive self-cleaning stainless-steel heat exchanger coupled with a secondary flat plate heat exchanger. Our combi models can deliver whole house heating and simultaneous domestic hot water. This model provides an input rating of 90K Btu. Fueled with either Natural Gas or Propane this Rinnai condensing gas boiler has obtained one of the highest AFUEs (Annual Fuel Utilization Efficiency) in the industry. Plus, the compact wall-mounted design saves space over traditional boilers.