Didier Stevens

I charged an iPad Pro (12.9 Inch) and measured the power consumption (at 120V and 230V). According to the specs, this iPad has a battery with a capacity of 40.88 Wh.

Procedure: when the iPad Pro turns itself of because of a low battery, I started to charge the iPad with an Apple A2347 USB C charger and measured the AC power consumption of this charger. It consumes around 21 Watt, this value starts to diminish when the battery approaches full charge. When at 100%, the charger will still deliver power, slowly decreasing to 3 Watts, and then it stops delivering power for charging. At that point, I stop the power consumption measurement.

I did not use the iPad while charging.

This measurement was done twice: at 120V 60Hz and 230V 50Hz (using an AC power supply).

There’s not much difference between the two measurements, but what I’ll certainly take away from this test, is that it takes around 57 Wh of AC power to charge a 40.88 Wh battery!

Update: when I did these tests, my iPad Pro had around 84 charging cycles.

I did not explicitly specify in my post “Quickpost: Standby Power Consumption Of My USB Chargers” that I did my tests here in Flanders, Belgium and thus that the mains electricity is 230V 50Hz.

I wondered what the results would be in other parts of the world, like the USA. To answer this question, I redid my tests with the USB chargers powered by an AC power supply that delivers electricity at 120V and 60Hz.

The devices I tested are:

1. Apple A1357
2. Apple A2347
3. Anker A2053

The no-brand USB charger was not tested, as the input specs specify 220V – 240V.

I connected each one to the AC power supply (120V 60Hz) and used a powermeter (GPM 8310, resolution 0,1 µW) to measure the standby power consumption over 24 hours.

This is the result:

24 hours is the measured data, the “1 hour” and “1 year” columns are calculated based on the 24 hours data.

And here is the summary for 120V and 230V:

It’s clear that my USB chargers consume less standby power at 120V 60Hz than at 230V 50Hz.

I did some tests with my USB chargers: how much power do they consume when plugged into a power socket without charging any device (standby)?

The devices I tested are:

1. Apple A1357
2. Apple A2347
3. Anker A2053
4. No-brand: Chacon EMP604USB

I connected each one to a powermeter and let it measure the standby power consumption for 24 hours.

This is the result:

24 hours is the measured data, the “1 hour” and “1 year” columns are calculated based on the 24 hours data.

The no-brand USB charger consumes the most: around 2 kWh per year, which is still less than a switched off Philips Hue lamp.

Using the same cost as for the Philips Hue lamp, that no-brand charger costs me around €1 if I would leave it plugged in for a whole year without letting it charge anything.