Do Christmas lights really interfere with Wi-Fi signals?

A telecom regulator in the UK is warning that the festive lights, and a slew of other common household items, can produce electromagnetic fields that block the transmission of radio waves that carry Internet signals, causing Wi-Fi service interruptions.

Ever notice your Wi-Fi signal slowing down or cutting out all together? Before you blame the router or the cable company, consider looking at a more common item: Christmas lights.

Electrical interference from the festive decorations, and many other household items, including microwave ovens, baby monitors, and cordless telephones, can disrupt Wi-Fi signals and cause interruptions, according to Ofcom, a British telecom regulator.

The watchdog says Internet service providers often receive complaints over the holidays about interruptions to Wi-Fi service, and the strings of lights may be a key reason.

The warnings about common household devices causing service interruptions are nothing new, although consumers may not think of them as the reason a Wi-Fi signal goes down, says a white paper released by Cisco.

To combat that, Ofcom is releasing its own Wi-Fi Checker app, which lets consumers in the UK use their smartphones and tablets to check whether they are getting the best connection possible. After running a series of tests, the company says, the app will offer simple troubleshooting steps to fix the problem.

But Christmas lights may not even be the worst offender, with a range of other household items also producing large electromagnetic fields that interfere with a Wi-Fi signal or absorb and block signals from being transmitted across a room.

That’s because Wi-Fi’s spectrum is on the unlicensed "industrial, scientific and medical" radio band, and shares similar frequencies with a range of other devices.

A running microwave oven, for example, uses microwaves at a frequency of around 2.4 GHz, which is in the same band as Wi-Fi, which makes it a virtual black hole for Wi-Fi signals, the Guardian notes.

Other common offenders include speakers, water pipes — which can absorb energy from the radio waves that carry wireless Internet and even household insulation, which can also absorb the signals coming through the walls. Overlap with other Wi-Fi networks from neighboring houses and buildings can also cause interference for a router.

In the UK, Ofcom notes that while fast broadband service is available in nearly 24 million homes and buildings, or 83 percent, and 13 million have access to 4G mobile service, the quality of the connection can vary widely, especially in rural areas. Wireless broadband may not be working as well as it should in 6 million homes and offices in the UK, the regulator found.

To fix many of these problems, you can try switching the channel that the router is broadcasting on (often done via software made by the Internet provider or the router’s manufacturer) and using equipment that broadcasts on the less widely-used 5 GHz band. Finally, the ultimate ho-hum solution may be to move offending devices, including Christmas lights, farther away from the router.