Wall Charger Verses 12v Car Charger Efficiency

Have you ever wondered which kind of charger is more efficient?  Are wall chargers we use to charge our devices just as efficient as 12v car chargers?  In this blog post, you’ll find out!

I grabbed 3 quality wall chargers and 3 quality car chargers with the intent to see how many watts each consumed, and how many they actually put into an Apple iPad Mini.  To find these measurements, I used a wall AC meter, a DC power meter, a USB dongle meter and an Anker 1 ft Powerline cable.  Here are the results.

Charger Watts In Watts Out Percent Loss
Apple 5 watt 6.6 watts 4.6 watts 30.3%
Apple 12 watt 11.6 watts 9.2 watts 20.7%
RAVPower iSmart 11.0 watts 9.1 watts 17.3%
PowerGen 20w car 8.9 watts 8.8 watts 1.1%
Anker 42w car 10.7 watts 9.9 watts 7.5%
Anker 24w car 8.2 watts 8.1 watts 1.2%

Wow!  I didn’t expect to see such a difference in efficiency between the wall chargers and the car chargers.  After a little digging, it makes sense – the wall chargers need to convert AC (alternating current) into DC (direct current), whereas the car chargers are just changing 12 volt direct current into 5 volt direct current that is the standard for USB.  Even the worst car charger was 10% more efficient than the best wall charger – crazy, right?

I suspected AC wall chargers were less efficient from my experience using my pedal generator.  I could see the wattage used by the wall chargers put more of a load than the DC car chargers, but it was great to quantify the real difference.  I had no idea how much more inefficient wall chargers were!  I will definitely be using car chargers whenever possible for the most efficient charging of my devices.  On the other hand, if I need more of a challenge on my pedal generator, I can always substitute in the AC chargers!

If you’re living off grid, you may find this information very helpful in deciding how you should charge your mobile devices.  Directly charging with solar or a pedal generator would be the most efficient way to go, rather than dumping all power to a battery bank, then converting to AC and charging with a wall wart (thoughts of all the efficiency losses in this cycle is making my head spin!).