What is RMS voltage?

Root mean square voltage is a statistical measure of how much alternating current power is needed to produce a similar heating effect to an equal direct current power. Root mean square can be found by taking the square root of the average of the squares of the measure values.

Alternating current, when graphed, is shown as a continuous sine wave of equal "hills" and "valleys." If, for example, an alternating current is measured over four peaks and four troughs, and the current at each peak is 10 amperes while the current at each trough is -10 amperes, then by adding the squares of each peak and trough, dividing the total by 8, and taking the square root, the root mean square voltage is exactly 10.