Starting motors under high loads also causes voltage drop which is often evidenced by flickering lights. Such voltage drop associated with motors is called voltage flicker.

This flicker is objectionable only when the magnitude and frequency of occurrence of the voltage drop exceed certain thresholds. The threshold of objection is shown on a Voltage-Flicker curve. If the magnitude of the voltage drop and the frequency of occurrence lie below the threshold of perception, people generally do not notice any flicker.