Flickering lights can indicate electrical problems ranging in severity from annoying to ominous. Because your lights are powered by your home's electrical system, the cause of flickering may be the lights themselves or it may be more of an electrical-system-wide issue. Diagnoses and solutions range from screwing in a light bulb to reaching out to a professional electrician.
The Simple Stuff
If the light from one fixture flickers, turn the light off and allow it to cool down, then tighten the bulb or switch out the existing bulb with a fresh one. If you have a compact fluorescent lamp bulb -- the spiral-shaped, energy-saving type -- in a socket connected to a dimmer switch, blinking may occur as these bulbs are not generally compatible with most types of dimmers.
Sometimes, starting a large appliance -- typically one that draws 100 amps or more, such as a heating or cooling unit or a clothes dryer -- may cause your home's lights to flicker. In this case, move the appliance to an outlet on a dedicated circuit to remedy the issue. If heating and cooling appliances cause your lights to flicker upon starting, contact a certified climate-control technician to install a soft start kit, which helps reduce the amount of power needed to start the appliance. Do not neglect power-draw problems, as long-term increased current draw may heat breakers or connectors and eventually lead to house fire.
Calling for Help
Consistent flickering in one or more areas that persists after you have changed the light bulb may indicate loose wiring, as can the dimming of lights. Because a single circuit can reside in places ranging from your junction box to your light switch, and because each circuit may have up to 50 connections, you'll need to enlist the help of a licensed electrician to identify and remedy the fault. If multiple lights flicker, this may indicate loose service conductors in your main electrical panel or meter base, typically caused by normal wear and tear as your conductors heat up and cool down each time you use them. Other causes of flickering lights that call for professional attention include faulty connectors, corroded wiring or a mixture of copper and aluminum wires that have not been properly connected.
More to Consider
Neglecting wiring or connection issues can increase your chances of a house fire, cause electric shock and compromise safety features such as breakers. If simple troubleshooting doesn't do the trick, don't hesitate to call a licensed electrician. Electric issues from outside your home may also cause flickering lights; if the wire that connects your home's electrical supply to your power company's transformer is too small, for instance, your lights may flicker. Contact your power company to investigate and address this issue.