Does micro-USB cable affect charging speed?

How much does a micro-USB cable affect the charging speed of your phone? Should you pay extra for a premium-quality cable? To find this out, I ran a small experiment.

For this experiment, I tried all combinations of four micro-USB cables I had lying around, two USB chargers, and three devices to be charged: a Sony smartphone running Android, a Samsung tablet also running Android, and a Mimacro power bank. As a proxy for charging speed, I used the power drawn by the charger measured by a Kill A Watt-like electricity monitor. To avoid batch effects, I tested combinations in a pre-determined random order.

It turns out that I had one particularly bad cable (“Cable 1”) that was 3-4 times less efficient at charging:

I do not remember how I got Cable 1—whether I bought it separately or it was included with some gadget—but superficially it looks better built than some of the other cables, so I was surprised by this result.

Other than that one cable, all cables were performing similarly, drawing around 9–11 watts, which at 5V corresponds to the current of 1.8–2.2A.

There also were no practically significant differences between different devices or chargers as the graphs below show (where Cable 1 measurements are excluded):

None of my devices are new, and none of my cables are particularly high-end, so your mileage may vary. But my conclusions from this are:

1. Do not buy the cheapest cable or charger, but it’s not worth investing extra either.
2. Do a quick test to see whether the cable/charger is drawing around 10W or 5A of electricity—do not rely on the “high-quality” look of it.