How to Calculate Load
- 1). Locate the electrical meter for your home. This is located at the point where the electric company provides power to you. The meters resemble a glass bubble with a face plate that indicates power usage on dials and a rotating disk.
- 2). Schedule various times during the next few days to go out and take meter readings. These should include times when your electric usage is at a minimum, at a maximum and at a time when usage is average.
- 3). Record the wheel multiplier for use in the calculations. Every revolution of the wheel is equal to a particular number of watts of energy. The value of each revolution is printed on the face of the meter. It is designated by the symbol Kh printed on the right side of the face plate.
- 4). Take your reading by watching the spinning wheel in the meter. Count how many times the wheel goes around during the amount of time measured by the stopwatch. To get a good estimate of the usage, especially during peak times when the wheel is moving fast, choose a time period that includes as many revolutions of the wheel that you want to count, between 6 and 10 is a safe number. Begin the stopwatch as the black mark on the wheel passes the middle point of the visible region of the wheel. Count the revolutions until you reach between 6 and 10 revolutions and then stop the stopwatch when the wheel returns to the middle part of the visible region again.
- 5). Calculate the energy usage for each time when you measured the wheel over the past few days. Use the equation, watts = (Kh * Rev * 3600) / T, where T = time in seconds, Rev = number of revolutions of the wheel, Kh is read from the meter and 3600 is number of seconds in 1 hour. For example, assume that the meter took 13 seconds to go around 6 times on a meter that had a multiplier value of 3.6. Insert the values that were collected into the equation and calculate the answer.
Watts = (3.6 * 6 * 3600) / 13 = 5,981.5 watts. If this data was for the period of most usage, then a 6 kW generator would work, but not if anything else was added to the home.
Source...