The devil is in the data collection!

May 10 – We are saving electricity once or twice weekly at River Oaks Academy thanks to the Eco-Footprint Challenge. But showing that savings has been harder than we thought!
We have turned off many classroom lights in the mornings or the afternoon or both for about 40 minutes. Students have plenty of sunlight for reading and other classroom work. We thought all we would need to do is write down the electric-meter reading each day to show our savings. But we have discovered that the meter reading only tells some of the story, because lights are not the only things that use electricity in our building.
For one thing, we know that on hotter days our building may start running the air conditioner. We also use power for running office equipment, kitchen stoves and dish washers, and our many computers. Each of those uses may change from day to day. And the biggest one, the air conditioning, can really make our electricity usage soar. Also, there may be special activities at the school that require more electricity for lights and heating or cooling.
Those are a lot of uses to try to keep track of when we measure how much electricity we save by turning off the lights. We have been averaging 2,400 kilowatt hours per day for the last couple weeks. yet for some reason, our electricity usage soared between May 1 and May 3, even though we turned off the lights for 40 minutes on May 3.