Power, Energy and the Loads List

"The Wattage of light bulbs and CFLs is easy to obtain: look at the labels on the devices."

How much energy is in a kWh?

To give you an idea, imagine that the 15-Watt CFL mentioned above was left on for 66 hours and 40 minutes. In that time, it would consume 1 kWh of energy. We know this because 1,000 (a kWh) divided by 15 (the power needed by the CFL) equals 66.67, which, in our equation, must be the hours figure.

Remember: Power x Time = Energy.

To complete a loads list, you will need to know the Wattage needed by every electrical device that will be used. The Wattage of light bulbs and CFLs is easy to obtain: look at the labels on the devices. Not all appliances list their power need on the label. That's often due to the fact that the device uses power differently at different times; an example is an electric range and oven. The power needed to operate it—and, consequently, how much energy it consumes over time—depends on how many burners are turned on, and to what settings, and whether the oven is on as well. Similarly, a refrigerator does not consume a steady amount of energy but actually cycles on and off throughout the day. (On average, a refrigerator "runs" about 13-15 hours per 24 hour day.) The only way to measure such devices' energy consumption is to track them over time and figure out a daily or monthly average.