Power Strip Clicks Randomly at Night

Quick Answer

The random clicking from a power strip at night is almost always the surge protection circuit (MOVs -- metal oxide varistors) clamping small voltage spikes from the utility grid. These minor surges are more noticeable at night because the house is quiet and many large appliances in the neighborhood cycle on and off. The clicking is the power strip doing its job. However, if the clicking is frequent, the surge protection may be wearing out and the strip should be replaced.

What Makes the Click

Inside a surge-protected power strip are components called MOVs (metal oxide varistors). These are the workhorses of surge protection. Under normal voltage (120 volts in the US), MOVs do nothing. When the voltage spikes above a threshold -- typically 330 to 400 volts for a residential surge protector -- the MOV absorbs the excess energy and diverts it to ground.

Each time an MOV activates, it dissipates a small amount of energy as heat and produces a faint click or pop. This is the sound you hear. The spike itself lasts microseconds, but the mechanical click of the MOV and the relay is audible.

The spikes that trigger these clicks are not dramatic events. They are small, transient voltage fluctuations caused by:

Motors cycling on and off. Refrigerators, HVAC compressors, pool pumps, and even appliances in neighboring homes create small voltage spikes on the shared electrical grid when they start and stop.
Utility grid switching. The power company regularly switches transformers, capacitor banks, and distribution lines, each of which can create minor transients.
Lightning in the distance. A storm miles away can induce small voltage spikes that travel through the power lines.
Electromagnetic interference (EMI). Electronic devices, especially those with switching power supplies, can introduce high-frequency noise that some surge protectors react to.

Why You Hear It More at Night

Two reasons. First, your house is quiet at night. The ambient noise during the day -- traffic, conversations, the TV, kitchen appliances -- masks the soft clicking. At night, in a silent room, even a quiet click is noticeable.

Second, electrical demand on the grid shifts at night. As businesses close and people go to sleep, large industrial loads cycle down and HVAC systems in surrounding homes adjust. Each transition creates small transients. Ironically, the quieter grid at night can have more per-event transients even though overall demand is lower.

Is the Clicking a Problem?

Usually, no. A surge protector clicking occasionally is doing exactly what you paid it to do -- absorbing small surges that would otherwise reach your electronics. Each click represents a spike that was intercepted.

However, MOVs have a finite lifespan. Each surge they absorb degrades them slightly. After absorbing enough cumulative energy, the MOV fails and can no longer protect against surges. Many quality surge protectors have an indicator light that shows whether the surge protection is still active. If this light is off or has changed color, the MOVs are spent and the strip is just a regular power strip with no surge protection.

Replace the power strip if:

The "Protected" indicator light is off or no longer illuminated
The clicking has become much more frequent than it used to be
You hear a loud pop followed by a burning smell (the MOV may have failed catastrophically)
The strip is more than 3 to 5 years old and has been in continuous use
The strip feels warm to the touch even with a light load

Other Sources of Clicking

Not every click comes from surge protection. A few other possibilities:

Thermal expansion. Cheap power strips with thin plastic housings expand and contract as they warm up and cool down. The plastic can click or creak as it shifts. This is more of a ticking than a sharp click and is harmless.

Relay-based outlets. Some power strips have individual outlet switches or master/slave configurations with internal relays. These relays can click when they detect a change in load, such as a device entering or leaving standby mode.

Poor contact. A loose plug in one of the outlets can arc intermittently, creating a clicking or popping sound. If you see a spark when plugging something in, and the strip's outlets feel loose, replace the strip. Arcing at a loose contact generates heat and is a genuine fire risk.

Reducing the Clicks

If the clicking bothers you, there are a few approaches:

Move the power strip. If it is in your bedroom and the clicking wakes you up, relocate it behind furniture or use an extension to position it farther from where you sleep.

Upgrade to a better surge protector. Higher-quality surge protectors use larger MOVs with higher joule ratings, which handle small surges without audible activation. A surge protector rated for 2,000+ joules will click less often than a $10 strip rated for 400 joules because its threshold is higher and its components absorb small events more quietly.

Consider a whole-house surge protector. Installed at the electrical panel, a whole-house surge protector intercepts surges before they reach individual circuits. The point-of-use power strip then sees much cleaner power and clicks far less. Whole-house surge protectors cost $200 to $500 installed and protect everything in the home, not just one outlet.

Check for a noisy circuit. If one particular outlet or circuit seems to generate more clicking than others, there may be a device on that circuit creating electrical noise -- a dimmer switch, a motor with worn brushes, or a malfunctioning appliance. Isolating and replacing the noisy device can clean up the circuit.