Before considering energy sources, the building needs to be sealed for maximum efficiency. At little to no cost, most buildings of a certain age can be upgraded to burn fewer watts. The point of an energy audit is to decrease the number of watts needs to use the building.
Lighting is a major consumer of watts. Heating is another area of concern followed by windows, doors and ducts. An energy audit covers every system in the building.
One congregation put a measuring meter on their commercial refrigerator and learned that a significant portion of their electric bill was used for a box that was designed to be opened 100 to 150 times a day and maintain a steady cold temperature. By swapping out the commercial model for two high efficiency home models, they cut their bill by fifteen percent (15%). Even on their busiest feast day, they do not open their refrigerators that often – unless you count the kids sneaking into the kitchen.