I love when people go out and actually test the hardware we rely on each day. That’s why I used to spend way too many hours running file-transfer tests for routers at Wirecutter, and why I love Lifehacker alum Eric Ravenscraft’s latest analysis that exposes some big problems with your phone’s wireless charging setup—problems we all have probably thought about at one point or another, but never put numbers to.
The evaluation seems so simple that I’m surprised I hadn’t run across it before. Eric teamed up with the right-to-repair wizards at iFixit to figure out just how much energy a typical wireless charger draws over the considerably longer amount of time it likely takes to juice up your smartphone. He then ran the same evaluation for a standard charging cable and power adapter.
For more on phone charging, check out the video below:
The results? Eric writes:
“Charging the phone from completely dead to 100% using a cable took an average of 14.26 watt-hours (Wh). Using a wireless charger took, on average, 21.01 Wh. That comes out to slightly more than 47% more energy for the convenience of not plugging in a cable. In other words, the phone had to work harder, generate more heat, and suck up more energy when wirelessly charging to fill the same size battery.”
Eric also found that how he positioned his phone on a wireless charger affected how many watt-hours it would take to charge his phone to full. This shouldn’t be very surprising to you: If you’re a little sloppy in how you set down your device, you’re not aligning the coils as well as you could be, so it’ll take more watt-hours for your device to charge. If your wireless charger is designed in such a way that it’s hard to ever miss the coils when you rest your phone on the charger, you’ll probably be more efficient in your charging.
But, as Eric maintains, wireless charging is still going to be inefficient in most scenarios. And the charger itself draws power, too: approximately 0.25 watts each hour, even if your phone isn’t sitting on it at all.
Don’t throw out those wireless chargers just yet, though
Should you go replace all of your wireless chargers with cables? Well, if you need the fastest charge you can get, it wouldn’t hurt. As Nick Guy wrote for Wirecutter last year:
“Qi wireless chargers are slower than wired chargers, full stop.
The fastest chargers we’ve measured in our testing recharged a fully drained iPhone XR to only 50 percent battery capacity in an hour, around half as fast as a wired charger. But any wireless charger can still fully charge any phone overnight. That’s why I also use one on my bedside table. If I wake up in the middle of the night and want to check my phone (bad habit, I know), I don’t have to worry about waking up my partner when I’m fumbling to plug my phone back in.”
And if all you care about is energy-savings—all of one LED lightbulb’s worth or so—then wired charging is the way to go, writes Android Central’s Jerry Hildenbrand:
“The too long, didn’t read explanation is that the most efficient way to charge your phone is the slowest way: a simple USB-A 5-volt 1-amp charger coupled with a short and stout cable plugged directly into your phone. It’s also a method that most people aren’t ever going to use because it’s super slow, and speed and convenience matter.”
I think this is the approach to take, because it’s important to be mindful of the power you’re using—especially when you think about the bigger picture. Using a wireless charger over a wired charger for your phone isn’t going to impact your electric bill to a noticeable degree. Go without one side order of fries at your favorite fast food place, and you’ll have easily covered that which you would have spent on a more inefficient wireless charger.
However, if everyone started using a wireless charger, then we’re all contributing to a huge resource suck for the slight extra convenience of not having to plug something in to charge it. Literally, that’s the only benefit right now to wireless charging: It’s slower, it’s more inefficient, but it doesn’t require you to plug in a cable—a process that typically takes only a few seconds, or about as difficult as throwing your recyclables in a blue bin instead of a black one.
I wouldn’t go throwing out your wireless charger, because that would probably waste as many resources, if not more, as simply using the charger. However, the inefficiencies of wireless charging is something to keep in mind going forward. As newer and better wireless chargers arrive, maybe consider sticking to cable when it’s not a burden to do so—when you’re working at your desk, for example, or about to go to sleep for the night—and use wireless charging for those few moments when you need extra convenience or otherwise can’t swap charging techniques, such as the fancy new wireless charging setup in your car.
And while you’re at it, do you really need to constantly charge your phone, anyway? Instead of continually boosting yourself up to a 100-percent charge from 80-percent, consider keeping your phone off the charger until you’re done for the day (or you really need more battery for a future outing you’re planning). Every little bit helps.