I cut my teeth in the heating industry during the height of the “solar era.” During this period the word “efficiency” must have received many nominations for the “Buzz Word Of The Year” award. Even today customers ask us about the efficiency of hydronic floor heating systems compared to other heating systems.
It’s hard to compare the efficiency of two processes, however, unless you define the word. The simplest definition is:
For example, suppose a boiler uses one gallon of No. 2 fuel oil to yield 98,000 Btus of heat. How efficient was this conversion? Well, the output quantity is 98,000 Btus of heat. The necessary input quantity was one gallon of No. 2 oil. To make the formula work the input and output quantities must be expressed in the same units. It’s easy to convert gallons of No. 2 oil to energy, just multiply by 140,000 Btu/gallon. The efficiency of the process is thus: