Do energy saving bulbs flicker when you turn them on?

With the newer more modern high quality LED bulbs and CFL’s they generally offer instant illumination, some flickering may occur but it is normally on the older, lower quality bulbs.

Compact fluorescent lamps (CFL’s)

CFL’s are generally phased out now but many of them are still in use. These bulbs often have noticeable flickering when first turned on.

Initial flickering - A CFL contains inert gas and a small amount of mercury vapour and when switched on an it initiates a high voltage charge from the ballast to excite the mercury vapour, which then emits ultraviolet light (UV).  This UV light hits a phosphor coating on the inside of the glass tube causing it to glow .  This start up process is not instantaneous.

Ongoing flickering (during operation) - CFL’s that are powered by magnetic ballasts normally flicker at twice the mains frequency (100 or 120 times per second),  a rate which is generally imperceptible to the human eyes but there are some people who are sensitive to it.

Light emitting diodes (LED’s)

LED’s are new technology and they do not rely on a gas or warm up periods which makes them an instant light up with no flickering.

Occasional turn on flickering - If a LED bulb does flicker when turning on it is usually one of two reasons

1. Driver instability - LED’s require a driver to convert the mains voltage to low voltage and a driver that is poorly designed or is failing could lead to a slight flicker or a delay in lighting up.
2. Dimmer switch incompatibility - If a LED is installed on a circuit with the old incandescent dimmer switch it could cause issues when turning on, to remedy this the switch should be changed on one that is designed specifically LED’s

Do cheap LED light bulbs flicker

A cheap LED saves money by omitting components required to produce a constant current for the LED’s which results in poor quality of light and a chance of flickering.