Gas Water Heater Ratings 2015 More Regulation The Final Rule Water Heater Efficiency Energy Factor Ef Energy Factor Is The Ratio Of Useful Energy Output From The Water Heater To The Total Amount Of Energy Delivered To The Water Heater
gas water heater ratings 2015 more regulation the final rule water heater efficiency energy factor ef energy factor is the ratio of useful energy output from the water heater to the total amount of energy delivered to the water heater.