Line regulation is defined as the percent of voltage variation derived from the voltage output of a given circuit or current. Currents and circuits should be measured around a house from time to time to determine whether the line regulation is too high for a given section. This can cause malfunctioning of appliances or even short circuiting. The formula for line regulation is very simple, and you will need a voltage output measuring meter to make the necessary calculations. Start by measuring the initial voltage output for a given circuit, then write down the largest deviation from this initial voltage over the next 10 measurements.
Things You'll Need
 Calculator
 Voltage output meter

Find the difference between the initial voltage and the maximum fluctuation. For example, if the initial voltage was 25 and the maximum measurement was 28, then the difference in voltage would be 3 volts.

Divide the change in voltage by the initial voltage. Using the above example, 3/25= .12

Multiply the number obtained in Step 2 by 100. This will give you the line regulation percentage for the circuit or current you are measuring. Ex: .12 x 100 = 12%