Why Do Light Bulbs Glow When Switched Off?

Have you ever noticed your light bulbs glowing even after you turn them off? Worry not; there’s absolutely nothing wrong with them. This phenomenon of light bulbs glowing even after you turn them off is called the “Afterglow Of Bulbs.” It is utterly common in LEDs, CFLs, and incandescent bulbs.

There are different reasons for a glowing light bulb even after turning it off. Some include poor insulation, lacking earthing wire, and more. Moreover, sometimes, using poor-quality light bulbs also lead to problem. If you’re concerned about your glowing light bulb despite turning it off, you’re at the right place.

This article deals with various reasons that lead to the glow of light bulbs even after it is turned off. Then you’ll see read remedies to stop this.

Reasons Behind Glowing Light Bulb When Switched Off

In this section, you’ll learn about a few top reasons that lead to a glowing light bulb.

  1. LED Drivers Store Energy

LEDs have an electric circuit called an LED driver. It contains a capacitor and an inductor to store electric current. So when the input voltage is switched off, it will begin to discharge the current from its peak value to zero.

Due to the high efficiency of LEDs, they operate on residual electricity. It gives a faint glow after it is switched off. LEDs continue to emit dim light till all the current is discharged. The time taken for the glow to fade may vary from seconds to minutes. That depends on the different light bulbs used.

  1. Problems With Electrical Wiring

Sometimes bulbs keep glowing due to some problems with electrical wiring. Problems include faults in wiring or high resistance. If not appropriately earthed, the neutral wire will carry electrical currents. As a result, the neutral wire will power up the bulb even after you turn off the light.

Also, you must insulate the wirings properly. Poor insulation, damaged insulators, or electromagnetic induction can cause faint glow in bulbs. A small electric current keeps passing due to poor insulation, resulting in a faint glow. Even some faults in cable routing can cause bulbs to glow after turning off.

Sometimes short circuits damage the electrical fitting. Short circuits don’t wear out the wire, so people keep using faulty wires. The faulty wire in your electrical fitting can also be the reason behind your glowing bulb.

  1. Poor Quality of Bulbs

There are a variety of light bulbs available in the market. They can be highly expensive than cheap products. To reduce production costs, manufacturers use inferior raw materials in production. Low-quality bulbs won’t last much longer and may develop issues. Unusual dimming, flickering, or glowing of the bulbs in a while, even when it is turned off, are common issues.

  1. High Operating Temperature

Incandescent bulbs produce hot white light due to their extremely hot filament. Switching off the light takes a few seconds for the filament inside the bulb to cool down completely. Hence the bulb continues to glow a little while the filament cools down.

In the case of LEDs, the diodes and drivers are stressed at higher operating temperatures. Higher junction temperatures result from higher operating temperatures. It can increase the degradation rate of LED junction elements. This potentially causes LEDs light output to decline irreversibly over time.

  1. Use Of Fancy Switch or Dimmers

Nowadays, many electric switches are available with more features than the usual ones. They come with motion detectors, timers, and indication lights.

Fancy switches require a small current to remain on standby. LEDs draw some current from these switches when switched off, shining faintly.

A similar problem arises when you connect electronic dimmers to your light bulbs. Electronic dimmers require adequate current to function properly. The bulb draws current from the dimmers to keep glowing even after the power cut-off. However, incorrect installation of the switch or dimmers can also cause such problems.

  1. Vaporizing Inside The Bulb

It’s a common issue for afterglow, found in CFL. Mercury vapor and phosphorous coating inside the tube react, producing light in CFLs.

When switched off, the current flow stops immediately. But the gases inside the bulb take a while to settle down. The electrons continue to release energy for a short time. Phosphorus interacts with the ionized mercury, producing leftover photons of visible white light.

light bulbs 2

Remedies To Stop Glowing Of Bulbs When Switched Off

Now let’s look at what you must do to stop your light bulbs from glowing after the switch is turned off.

  1. Check Your Electric Wiring

Seek help from an electrician who can test the whole electric wiring for you. If you know how to test the electric circuits of the light bulb, you can check each of the circuit wires by yourself. Always avoid using poor-quality wires in your primary electrical fitting. Moreover, avoid using faulty wires, which have experienced short circuits. Sometimes bugs and pests chew out electrical wires, which you must avoid using.

  1. Install A Zener Diode

The Zener diode helps in regulating the voltage in your electrical circuit. It is well capable of handling voltage breakdowns. A Zener diode in a protection circuit helps restrict glowing bulbs after you turn them off. If the bulb still glows, install another Zener diode in the circuit. 

  1. Replace Your Bulb

If you’re using a poor-quality light bulb, upgrade to a higher-quality one to solve this issue. Good quality LEDs or incandescent bulbs are quite long-lasting. They’re more efficient in avoiding the problems of glowing bulbs when you turn off the switch. Manufacturers back quality bulbs with a warranty, which indicates quality assurance.

  1. Install A Bypass Capacitor

Make sure you install a bypass capacitor near your power supply pin. Capacitors restrict current from traveling far from the supply pin in two-way connections. Thus, place extra capacitors if 2+ conductors are in a parallel connection. You should call an electrician for bypass capacitor installation, though.


So it is very important to identify what is causing your bulb to emit faint light. After identifying the issue, get it checked by an electrician to stop the bulbs from glowing.

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