LED bulbs that glow when switched off

An LED needs almost nothing to produce a visible glow. A fraction of a watt reaching the driver is enough to light the room's darkness, which is why a problem that would have been invisible with a 60W incandescent is obvious with an LED.

On a dimmer, the cause is documented. Lutron states that when the lights are turned off, a small amount of electricity may still flow through the dimmer and the LED lights, which may cause the lights to glow or flicker even though they were turned off.

On a smart switch it is deliberate. Lutron again: a smart dimmer or digital switch must receive a small amount of power even when it is turned off. Where there is no neutral to carry that current, it goes through the bulb - the same mechanism described in smart switches when you have no neutral wire.

1. Check compatibility first. Lutron's first recommendation is to make sure the dimmer and the bulbs are compatible, using its own compatibility tool. This costs nothing and it is the most common cause of a mismatch. The general principle is in dimmer and bulb compatibility.
2. Fit a bypass capacitor at the fixture. Lutron's LUT-MLC is published for switches controlling CFL, LED and fluorescent lighting without a neutral connection available. Its instruction sheet says only one is required per switch, wired at the fixture between the switched hot and the load. It also carries the only safety warning in this whole topic: turn off power at the circuit breaker before installing.
3. Move to a neutral-required dimmer. If there is a neutral in the box and you are using a two-wire dimmer anyway, this removes the leak at its source rather than absorbing it.
4. Add one incandescent or halogen bulb to the circuit. Lutron offers this as a last resort: if you do not want to change all of your LED lamps, inserting an incandescent or halogen bulb can help stabilize the other lamps and improve dimming performance. It works because the filament gives the leakage somewhere harmless to go.

Lutron Maestro LED+ dimmer - the mainstream fix. A dimmer designed around modern LED loads, from the manufacturer whose support pages document this problem and publish the compatibility tool that resolves most of it.

Lutron Caseta dimmer - if you are going smart anyway. It is the best-documented no-neutral smart dimmer, with published minimum loads - and the same maker sells the bypass capacitor if your fixture needs one.

Philips Ultra Definition A19 - a bulb worth testing with. When you are checking a compatibility list, it helps to have one well-specified, widely-listed dimmable bulb to test against rather than a mixed handful of unknowns.

None of this is urgent if the glow does not bother you. It is a small current and the bulb will not wear out noticeably faster for it. The reason to fix it is usually that it is in a bedroom.

Note what is on the wall. A plain toggle, a dimmer, or a smart switch. That single fact narrows the cause more than anything else, because the documented explanation is specific to dimmers and digital switches.

Count the bulbs on the circuit. A single bulb is the hardest load for a dimmer to behave with, and glow is one of the symptoms.

Swap one bulb for a known compatible model and watch overnight. If the glow follows the fixture rather than the bulb, the control is the cause.

If the light also flickers while on, treat that as the same investigation - the diagnosis is in why dimmable LED bulbs flicker.