Wireless Charging Is a Disaster Waiting to Happen
We crunched the numbers on just how inefficient wireless charging is — and the results are pretty shocking
Wireless charging is increasingly common in modern smartphones, and there’s even speculation that Apple might ditch charging via a cable entirely in the near future. But the slight convenience of juicing up your phone by plopping it onto a pad rather than plugging it in comes with a surprisingly robust environmental cost. According to new calculations from OneZero and iFixit, wireless charging is drastically less efficient than charging with a cord, so much so that the widespread adoption of this technology could necessitate the construction of dozens of new power plants around the world. (Unless manufacturers find other ways to make up for the energy drain, of course.)
On paper, wireless charging sounds appealing. Just drop a phone down on a charger and it will start charging. There’s no wear and tear on charging ports, and chargers can even be built into furniture. Not all of the energy that comes out of a wall outlet, however, ends up in a phone’s battery. Some of it gets lost in the process as heat.
While this is true of all forms of charging to a certain extent, wireless chargers lose a lot of energy compared to cables. They get even less efficient when the coils in the phone aren’t aligned properly with the coils in the charging pad, a surprisingly common problem.
To get a sense of how much extra power is lost when using wireless charging versus wired charging in the real world, I tested a Pixel 4 using multiple wireless chargers, as well as the standard charging cable that comes with the phone. I used a high-precision power meter that sits between the charging block and the power outlet to measure power consumption.
In my tests, I found that wireless charging used, on average, around 47% more power than a cable.
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.
How the phone was positioned on the charger significantly affected charging efficiency. The flat Yootech charger I tested was difficult to line up properly. Initially I intended to measure power consumption with the coils aligned as well as possible, then intentionally misalign them to detect the difference.
Instead, during one test, I noticed that the phone wasn’t charging. It looked like it was aligned properly, but while trying to fiddle with it, the difference between positions that charged properly and those that didn’t charge at all could be measured in millimeters. Without a visual indicator, it would be impossible to tell. Without careful alignment, this could make the phone take way more energy to charge than necessary or, more annoyingly, not charge at all.
The first test with the Yootech pad — before I figured out how to align the coils properly — took a whopping 25.62 Wh to charge, or 80% more energy than an average cable charge. Hearing about the hypothetical inefficiencies online was one thing, but here I could see how I’d nearly doubled the amount of power it took to charge my phone by setting it down slightly wrong instead of just plugging in a cable.
Google’s official Pixel Stand fared better, likely due to its propped-up design. Since the base of the phone sits flat, the coils can only be misaligned from left to right — circular pads like the Yootech allow for misalignment in any direction. Again, the threshold was a few millimeters of difference tops (as seen below), but the Pixel Stand continued charging while misaligned, albeit slower and using more power. In general, the propped-up design helped align the coils without much fiddling, but it still used an average of 19.8 Wh, or 39% more power, to charge the phone than cables.
On top of this, both wireless chargers independently consumed a small amount of power when no phone was charging at all — around 0.25 watts, which might not sound like much, but over 24 hours it would consume around six watt-hours. A household with multiple wireless chargers left plugged in — say, a charger by the bed, one in the living room, and another in the office — could waste the same amount of power in a day as it would take to fully charge a phone. By contrast, in my testing the normal cable charger did not draw any measurable amount of power.
While wireless charging might use relatively more power than a cable, it’s often written off as negligible. The extra power consumed by charging one phone with wireless charging versus a cable is the equivalent of leaving one extra LED light bulb on for a few hours. It might not even register on your power bill. At scale, however, it can turn into an environmental problem.
“I think in terms of power consumption, for me worrying about how much I’m paying for electricity, I don’t think it’s a factor,” Kyle Wiens, CEO of iFixit, told OneZero. “If all of a sudden, the 3 billion[-plus] smartphones that are in use, if all of them take 50% more power to charge, that adds up to a big amount. So it’s a society-wide issue, not a personal issue.”
To get a frame of reference for scale, iFixit helped me calculate the impact that the kind of excess power drain I experienced could have if every smartphone user on the planet switched to wireless charging — not a likely scenario any time soon, but neither was 3.5 billion people carrying around smartphones, say, 30 years ago.
“We worked out that at 100% efficiency from wall socket to battery, it would take about 73 coal power plants running for a day to charge the 3.5 billion smartphone batteries once fully,” iFixit technical writer Arthur Shi told OneZero. But if people place their phones wrong and reduce the efficiency of their charging, the number grows: “If the wireless charging efficiency was only 50%, you would need to double the  power plants in order to charge all the batteries.”
If everyone in the world switched to wireless charging, it would have a measurable impact on the global power grid.
This is rough math, of course. Measuring power consumption by the number of power plants devices require is a bit like measuring how many vehicles it takes to transport a couple dozen people. It could take a dozen two-seat convertibles, or one bus. Shi’s math assumed relatively small coal power plants outputting 50 MW, as many power plants in the United States are, but those same needs could also be met by a couple very large power plants outputting more than 2,000 MW (of which the United States has only 29).
However, the broader point remains the same: If everyone in the world switched to wireless charging, it would have a measurable impact on the global power grid. While tech companies like Apple and Google tout how environmentally friendly their phones are, power consumption often goes overlooked. “They want to cover the carbon impact of the product over their entire life cycle?” Wiens said. “The entire life cycle includes all the power that these things ever consumed plugged into the wall.”
There are some things that companies can do to balance out the excess power wireless chargers use. Manufacturers can design phones to disable wireless charging if their coils aren’t aligned — instead of allowing excessively inefficient charging for the sake of user experience — or design chargers to hold phones so they align properly. They can also continue to offer wired charging, which might mean Apple’s rumored future port-less phone would have to wait.
Finally, tech companies can work to offset their excesses in one area with savings in another. Wireless charging is only one small piece of the environmental picture, and environmental reports for major phones from Google and Apple only loosely point to energy efficiency and make no mention of the impact of using wireless chargers. There are many ways tech companies could be more energy-efficient to put less strain on our power grids. Until wireless charging itself gets a more thorough examination, though, the world would probably be better off if we all stuck to good old-fashioned plugs.
Update: A previous version of this article misstated two units of measurement in reference to the Pixel Stand charger. It consumes 0.25 watts when plugged in without a phone attached, which over 24 hours would consume around six watt-hours.