Has this ever happened to you: you’re using your hairdryer and suddenly the lights in the bathroom start dimming? Or you’re reading in the living room and for no apparent reason the recessed lights start flickering. Flickering or dimming lights can be a cause for concern—a possible sign that something big or small is on the fritz. But what causes flickering, what causes dimming, and what’s the difference? For homeowners, they are both little hints from your house that you need to pay attention to.
Lights flickering in house? The difference between flickering vs. dimming lights
First, we need to differentiate between lights flickering in house and lights that are dimming.
“A flicker refers to the specific situation where lights are brightening and dimming rapidly—more than once per second,” says John A. Orr, professor emeritus of electrical and computer engineering at Worcester Polytechnic Institute in Massachusetts. “This is different from the situation where the lights dim, and stay at the lower brightness for some time.”
Lights flickering in house: harmless reasons why it happens
Lights can flicker for a number of reasons, some of which are harmless and others that are hazardous. A lamp or light fixture that’s flickering most likely has a loose lightbulb—and that’s no big deal. You can easily test it by giving the bulb another turn and seeing if the flickering goes away. If the light still flickers, unplug it and plug it in again—the second most common reason that a light fixture flickers.
Another situation that’s not very dangerous, though very annoying, is when a ceiling fixture that’s on a dimmer flickers when set on low. This usually indicates that you’re using an incompatible lightbulb for the fixture—for example, maybe you’re using LED bulbs in a fixture not wired for LED.
“The solution is to try a different type or brand of lightbulb, or change the dimmer itself,” suggests Orr.
Another, very rare, reason for flickering lights has to do with having some large electrical load outside the house, such as in a factory operating nearby, Orr says. “This is not generally dangerous to the household, but can reduce the life of appliances and should be reported.”
If the flickering is not isolated to one particular light fixture—for example, if all the recessed lights in the room are flickering—that is the most dangerous flickering, and indicates that “there is a loose connection in the house somewhere between where the electrical service enters the house and the light,” Orr says. This should be addressed by a professional electrician ASAP.
Lights flickering in house or dimming when an appliance is running
Some people may observe flickering or dimming activity only when a certain appliance or pair of appliances is running.
“If the lights dim when an appliance starts (and perhaps brighten after a second or so), the most likely explanation is that the wiring is inadequate from the service entrance to the appliance,” Orr says.
“If it is a flicker, not a dimming, then either the appliance is drawing a large and varying current, which is quite unusual in households, or the appliance is literally causing something to vibrate and loosen a connection,” he adds. “Or if the lights are on dimmers, the dimmers are being interfered with by the characteristics of the appliance,” Orr says.
This type of interference is unusual, but the prevalence of Wi-Fi and electronics in general are making it more common than before.
Should you fix lights flickering in house yourself or call an expert?
Some level of DIY troubleshooting can be effective. If a dimmer switch is suspected, try replacing an LED bulb with a traditional incandescent bulb to see if that solves the problem.
However, if the problem requires more than a simple fix like changing a lightbulb, consult a professional electrician.
“Other signs of electrical problems include blown fuses or tripped circuit breakers, unusual sounds (such as sizzling or cracking), and burning smells emitting from an appliance,” says Raymond Williams, battalion chief of the Birmingham Fire and Rescue Service Department in Birmingham, AL. These situations all require the intervention of an electrician.
Since overloaded circuits can cause flickering, Williams warns against plugging washing machines, dryers, wall air conditioners, and microwaves into extension cords or power strips.
“These appliances should be plugged directly into the outlet,” he says, “and if you don’t have enough, an electrician can add additional outlets or circuits.”
When in doubt, Williams says it’s always better to be safe than sorry.
“You don’t want to become a fire statistic,” he says. “If you notice erratic behavior, unplug the appliance until you can contact a qualified professional to diagnose the problem.”