Why do lights flicker?

It's a common question we hear:  "My lights sometimes dim or flicker, is that dangerous?" 
Usually not, but it can be a sign of a problem. 
Basically, light brightness is a function of your house voltage -120 volts.  If the voltage drops, the lights will dim a little.  That's not a problem if it's due to a big appliance starting (refrigerator, a/c, iron, hair dryer, etc.)  Think of it as it taking extra work to get the refrigerator going so the voltage strains a little. 
However if the lights get brighter than normal, that's a sign of a bad connection in the wiring.  It's causing the voltage to drop and jump, also called a surge.  A higher voltage can damage the electronics in your house: TV, DVR, etc.  That's not good.  And since these things do not fix themselves and will only get worse, you should call us sooner rather than later.  
Flickering lights are also an indication of a bad connection that has gotten worse. One cause is tiny sparks in a connection, causing heat in the connection, and the heating and cooling of the connection makes things get worse.
I hope this explanation helps 'enlighten' everyone.
(More info about surges and surge protection, click here.)