How to compare charging on a power strip and outlet

Does your phone or laptop charge more slowly when its charger is plugged into a power strip? A normal, undamaged power strip should not make a USB charger charge more slowly. A poor connection, a faulty strip, or different test conditions can make it seem that way.

Use the same device, charger, and cable for both tests. The Charger & Cable Test can show charging speed as a percentage per minute on devices whose browser reports battery information.

Compare the power strip and wall outlet

1. Open the Charger & Cable Test on the device you are charging. If the tool does not show battery information, your browser may not provide the data needed for this comparison.
2. Choose an undamaged power strip and a wall outlet in the same room. Use the same charger and cable for both. Do not use a strip that is overloaded, hot, cracked, or loose.
3. For the first reading, connect the charger to the power strip and the device to the charger. Let the device rest, with its screen off and demanding apps closed. If convenient, start when the battery is below about 50 percent.
4. Watch the displayed charging rate for 5 to 10 minutes and note the result, starting battery percentage, and whether the device felt warm. Avoid drawing a conclusion from a brief change in the percentage.
5. Repeat with the charger plugged directly into the wall outlet. Keep the device, charger, cable, room, and device use as similar as possible. For a stronger comparison, repeat both tests later at a similar battery level.

Move the charger only by its insulated plug, and disconnect it from the device before changing the power source. If you notice heat, crackling, a burning smell, or a loose connection, stop using that outlet or strip rather than continuing the test.

What the result means

The charging rates are close

The power strip probably is not affecting charging. Small differences are normal because battery percentages are rounded and the charging rate changes as the battery fills. A difference in one short test does not prove that the strip is slower.

The wall outlet is consistently faster

Repeat the comparison before blaming the strip. If the result happens again under similar conditions, check that the charger fits securely in the strip and that the strip is in good condition. A loose or damaged connection can interrupt power. If the strip has a USB charging port, compare using the same charger plugged into the strip's regular outlet, not the strip's USB port, so you are testing the power source rather than two different chargers.

The power strip is consistently faster

This does not mean the strip supplies more charging power. The battery may have been at a different charge level or temperature, or the device may have been doing more work during the wall-outlet test. Repeat with the same setup and similar starting conditions. If the result changes from run to run, the test is not isolating the outlet as the cause.

The rate is low or does not appear

Check that the charger is connected and the device indicates it is charging. The browser may not report battery information on that device, and the test cannot measure charging speed if it has no battery data to read. If the device is not charging, troubleshoot the charger, cable, connector, and outlet rather than relying on a missing browser reading.

What to check if charging seems slow

1. Check the strip and outlet connection. Make sure the plug sits firmly and the strip's switch is on. Try another outlet only if the current one shows no signs of damage.
2. Keep the charger and cable the same. A different cable or power adapter can change the result. If you need to test another one, change only that part and compare again.
3. Let the device cool and rest. Charging may slow when a device is hot or busy. Remove it from direct sunlight, stop games or video playback, and leave the screen off during each reading.
4. Check for a charging limit. Some devices pause or limit charging to protect the battery. Keep any charge limit or battery care feature in the same state during both tests so it does not skew the comparison.
5. Stop using a suspect strip. Do not overload it or connect one power strip to another. If it is damaged, unusually hot, buzzing, or smells burnt, unplug it if safe and replace it. Do not open it or attempt an electrical repair.
6. Test the charger elsewhere. If charging is slow from both sources, try a compatible, known-good charger and cable. If the device still charges slowly, its charging port or battery may need inspection.

Why charging rates change during a test

Charging is not a constant flow. A device often accepts power faster at a lower battery level, then slows as the battery fills or warms up. The percentage-per-minute reading is a useful way to compare setups, but it is not a direct measurement of charger wattage, voltage, or electrical safety. A web page cannot certify that a power strip or outlet is safe.

If you also want to compare charging at two separate wall outlets, see how to compare charging speed at two wall outlets.