A brownout is a temporary interruption of power service in which the electric power is reduced, rather than being cut as is the case with a blackout. Lights may flicker and dim, and the event also often wreaks havoc with electrical appliances such as computers. This could be considered the opposite of a power surge, an electrical event in which a sudden burst of power enters the system.
There are a wide ranges of causes for brownouts. Just like blackouts, overloads on the electrical system can trigger one, as the generating facility is unable to provide enough power. It can also occur when events such as storms disrupt the distribution grid, or when there are other problems in the system. They can last for a few seconds or a few hours, depending on the cause and how quickly a power utility can get full power running again.
In some cases, a brownout is actually deliberate, in which case it is known as a voltage reduction. Voltage reductions are undertaken when utilities sense that a disruption in the grid may lead to serious problems. Rather than instituting rolling blackouts, the utility may temporarily cut voltage to some customers in an attempt to stabilize the grid and to allow reserves of power to accumulate again.
During a brownout, customers should turn off appliances like computers, as the irregular power supply can damage them. It is also a good idea to turn off lights, leaving one on to alert the customer to the restoration of full power. He or she may also want to check with the neighbors; if a single house is the only one out, there may be a problem with the power supply in that residence, and the owner should take a look at his or her circuit breakers. The resident may have inadvertently caused a problem by overloading the home's capacity to carry power, for example.
If a single house is not the only one affected, individuals can call their power company for information. If information is not available, the caller can report it to the utility, as they may not be aware of the problem. Rapid reporting can help the utility fix the problem quickly. When a brownout occurs during hot weather, homeowners should make sure to keep their refrigerators closed and keep themselves cool; people who are susceptible to heat, such as the elderly, should consider seeking out an air conditioned location to wait out the power issues.