Brownouts and blackouts are two types of electrical events. You’ve probably heard of blackouts or experienced them inside your home; blackouts happen when a building or service area loses power completely. On the other hand, brownouts are only partial outages. Both of those events are due to interruptions in the electrical service.

Those interruptions result from a variety of possible sources and may be intentional or unintentional. This article will describe the differences between brownouts and blackouts, and it will identify possible causes of each.



Brownouts are partial power outages due to a drop in voltage. In many cases, brownouts are forced by the utility company; although brownouts may be unplanned due to extreme weather or appliances drawing too much current, they are often deliberate efforts to relieve the electrical grid. Brownouts usually last for only a short while, and the utility company will typically know the expected duration of deliberate brownouts.

We call these events “brownouts” because lights may dim due to the reduced voltage.

Utility companies may plan brownouts to avoid an eventual blackout from an overloaded power grid. That’s why brownouts are particularly common during heat waves in the summer; when more people rely on electricity to cool down, the power grid has a harder time keeping up.

In many cases, home appliances won’t be at risk of failure due to a brownout. However, more sensitive devices that require a specific voltage range may be at risk. For example, some HVAC and refrigeration boards have a specific voltage tolerance, and excessive or insufficient voltage may cause premature failure. Some motors also fall into that category. If that equipment is expensive or assists in the production or sale of goods, the losses that result from brownouts may wind up being very costly.



Brownouts pose two threats to appliances: (1) decreased voltage and (2) power surges when normal voltage is restored.

Some circuit boards and controls for HVAC/R equipment, like the White-Rodgers SureSwitch, come with built-in brownout protection. In the case of the SureSwitch, the control reads the line voltage and detects significant drops that last for a minimum time period. (For example, if the line voltage should be 240v but the brownout protection reads 180v for more than 4 seconds, the control will shut off to protect itself. That way, the equipment is not exposed to sustained low voltage.

We also have to consider protecting vulnerable electronic systems from the power surges that may occur after a brownout. Small appliances can typically stay unplugged until the power has been running at its normal level for at least 10 minutes. However, larger appliances and electrical equipment may benefit from surge protection. Surge protectors like the ICM493 (pictured above) shunt the excessive power to ground so that the high voltage can’t reach your appliances. At Kalos, we offer the ICM493 for use on HVAC equipment; you can also select the ICM493 as an upgrade when you use our instant-quote feature.

When you have sensitive electronics or appliances in the home, you might also consider investing in an uninterruptible power supply (UPS). A UPS uses a backup battery to supply the usual voltage to appliances during a low-voltage event like a brownout. Gaming consoles, routers, modems, and other electronics may benefit from a UPS during brownouts.



As stated earlier, blackouts are total power outages, and they are often unpredictable. Whereas utility companies that plan brownouts usually know when the brownout will stop, the duration of a blackout can be highly variable and difficult to pin down.

In Florida, we see quite a few extreme weather events. Extreme weather may directly or indirectly cause blackouts.

Those of us who have lived here for a long time have likely seen tropical storms and hurricanes knock out the power; high winds may damage power lines, and trees may fall onto power lines and interrupt service. Outages caused by those types of extreme weather events may last for several days at a time. Thunderstorms are also pretty common here, and a blackout may occur when lightning strikes a power pole.

Blackouts may also happen when cars crash into utility poles or power boxes. A car could destroy the power box or knock over a pole, which would result in a total outage until the pole or box is repaired.

In most (but not all) cases, the utility company itself is NOT responsible for blackouts. As stated previously, the utility company should usually try to force a brownout if the grid could be unstable due to overuse.

As with a brownout, a power surge may occur when the power comes back on after a blackout. If you don’t take the proper precautions to protect your appliances and electronics, those things could be damaged.



When a blackout occurs, the best thing you can do is unplug your electronic devices and appliances. However, you might not be inside your home during a blackout and cannot unplug everything in the building. If unplugging everything is not a realistic option, we can consider using surge protectors or suppressors.

Surge protectors at outlets can help prevent damage to appliances and electronics; surge protection strips can usually protect multiple devices, and they contain fuses that become destroyed during power surges. When those fuses break, the high voltage can’t make it to your appliances because the circuit is incomplete. Whole-house surge suppression, which involves the placement of a single surge suppressor at an electrical panel, may also be worth considering. A whole-house surge suppression system will protect all of the electrical appliances in your home at once; one suppressor at the electrical panel could do the job of several surge protection strips.

Moreover, some people might hire an electrician to install meter-mounted surge protection. (Note: community standards and codes may forbid meter-based protection, so the option isn’t available to everyone.) Meter-based surge protection will protect all electrical appliances in your home from surges that come from the electrical service. However, you should note that meter-based surge protection does NOT protect the home from surges from the telephone lines or cable providers. Meter-mounted surge protection is just a piece of a surge-prevention strategy.


Brownouts and blackouts are simply power outages. They just happen for different reasons and represent varying degrees of an outage. In any case, the real danger to equipment usually comes from the power surges that may happen after brownouts and blackouts. We can protect our appliances with surge suppressors at appliances, outlets, the electrical panel, or even the electrical meter to prevent power surges from destroying electronic devices and appliances.