Let’s start with the simplest problems and their solutions first, then ramp up to more complicated issues:

1) A single light blinking - This most likely causes are a bulb that is loose in the socket, a defective bulb, or a deteriorated connection inside the wall switch. Try tightening the bulb connection (it might be too hot to touch if recently on, so wait a minute before checking). If that doesn’t fix it, then turn the wall switch on and off several times to observe any flickering when turned on and off, or an arcing sound at the switch. Replace the wall switch if this is the problem. 

2) Bulb is energy-saver compact fluorescent (spiral bulb) connected to a  dimmer switch - Older CFL bulbs don’t function properly when connected to a dimmer switch and may blink. Change out the dimmer for a regular switch or get one of the newer CFL bulbs that are rated for use with a dimmer. We don’t see to many CFL bulbs anymore.

3) Bulb is an LED (light-emitting diode) connected to a dimmer switch for incandescent lights - Not all LED bulbs are designed for use with a dimmer. If it doesn’t say so on the packaging, it probably isn’t. Some bulbs simply shut off as the dimmer reduces the current flow, others will dim but flicker at certain points in the range, or flicker intermittently at random when dimmed. Changing out the dimmer for a standard on/off switch is a cheap solution, or get an LED bulb that is rated for a dimmer. Better yet, also change out an incandescent-rated dimmer for one specifically made to be paired with LED bulbs.

4) Lights dim briefly when air conditioner kicks on - The surge of electricity necessary to start a air conditioning compressor moving can momentarily starve the rest of a home’s electric system of voltage, causing split-second dimming.

5) Lights on only one circuit blink - The problem is likely at a the circuit breaker or neutral wire connection in the panel. The heat generated by a bad connection may be enough to discolor or even melt the adjacent wire insulation and darken the area of exposed wire. Then again, the bad connection may not get hot enough for any visible signs, plus you have to remove the panel’s dead front to check this—which is not recommended unless you have electrical wiring experience. “There’s a good reason they call it a ‘dead’ front,” one electrician we know likes to ominously tell customers.

6) Lights are flickering throughout the house - The problem is likely at the main service cable connections or meter box connections, and will require examination by an electrician. These are high capacity wires and could be a fire hazard if not addressed quickly. 

7) Lights are flickering at neighbors’ houses too - It is a problem with the electric utility service, either at a shared transformer or area-wide issue. Call and report it for repair.

8) Mysterious, erratic flickering - When it only happens at random and has no detectible pattern, call an electrician. There are several rather complicated scenarios that can only be detected by following a patient, professional troubleshooting sequence.

    Also, see our blog post What do I need to know about buying a whole house surge protector?

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Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:

• Which house appliances need a dedicated electrical circuit?

• Can a short circuit cause a high electric bill?

• What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?

• Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?

• What causes copper wires to turn green or black in an electric panel?  

• What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?

• Why is it unsafe to bond neutral and ground wiring at subpanels?

• Should I get a lightning rod system to protect my house?

• Why is a strain relief clamp necessary for the cord connection to some electric appliances?  

• Does a wire nut connection need to be wrapped with electrical tape?

• What is the minimum clearance of overhead electric service drop wires above a house roof?

• What are the requirements for NM-cables entering an electric panel box? 

• What is the color code for NM cable (Romex®) sheathing?

• Why is undersize electric wiring in a house dangerous? 

• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

• How can I find out the size of the electric service to a house?

• Can old electrical wiring go bad inside a wall? 

• What is an open electrical splice?

• What is "knob and tube" wiring?  

• What is the code requirement for receptacle outlets in a closet?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.