Wireless charging is the future of charging for our phones, smartwatches, and earbuds. Maybe you’ve already ditched all wired chargers in favor of a couple of Qi wireless charging pads. But one burning question remains unanswered: Should you unplug your wireless charger when you’re not using it?
Qi-certified wireless chargers are safe but are also small electric appliances and should be unplugged when not in use, according to some manufacturers and agencies like the CPSC. Although unlikely, a metal object could land on the charging pad and cause it to overheat. Also, the constant flow of electricity may reduce its lifespan.
As we see wireless charging permeate our lives, you can learn everything you want to know about leaving your wireless chargers plugged in. We will also set them against their wired counterparts to see the differences in safety and power efficiency.
Is It Safe to Leave a Wireless Charger Plugged in All the Time?
First of all, wireless chargers are considered safe in general and when they are not connected to a smartphone or a tablet. When plugged in, wireless chargers emit a search signal and are looking for a wireless charging receiver coil, like the one in a smartphone or tablet. Wireless charging also emits less radiation than a phone connected to a mobile network.
It is considered safe to leave your Qi-certified wireless charger plugged in for extended periods and intermittently. Although a foreign metal object could cause it to overheat, it’s unlikely, thanks to Qi’s Foreign Object Detection (FOD) technology. The wireless charging pad stays off until you place your certified device on it.
An excellent resource is from Belkin in their article “Wireless Chargers Explained, Is Wireless Charging Safe?” The answer is most assuredly yes as long as you stick with Qi Certifed products.
All major phone manufacturers use the Qi wireless charging standard, but some are better than others:
So, it’s safe to assume that your wireless charger has Qi’s FOD baked into it. FOD is highly effective at recognizing whether the object you placed on top of it is a compatible device or not.
What is FOD In a Wireless Charging Device?
In Wireless Power Transfer (WPT), such as wireless chargers, Foreign Object Detection (FOD) is required for Qi Certified products by the Wireless Power Consortium (WPC).
This requirement indicates that in Qi-Certified products, a wireless charging systems transmitter can detect if an object other than what is being charged, such as a foreign object like metal or a coin, is on its surface. When this happens, the wireless charger stops charging.
According to the Wireless Power Consortium, Qi Specification PDF download page, Mechanical, Thermal, and User Interface Qi-v1.3-Mech-therm document it states the following:
“A Power Transmitter Product should indicate the following condition to a user: Indication to a user if a Foreign Object has been detected.”Qi Certified products by the Wireless Power Consortium (WPC) Download the Qi Specifications
Why You Want Foreign Object Detection
On the Wireless Power Consortium website, in an article titled “Beware of Fake Wireless Phone Chargers,” it states:
“Objects placed in the vicinity of wireless chargers, or between the charger and the phone, must not get hot to prevent injury such as 3rd-degree skin burns. The Qi specification mandates foreign object detection measures that help prevent this from happening”.Qi Certified products by the Wireless Power Consortium (WPC) – Beware of Fake Wireless Phone Chargers
Suppose a wireless charger does not have Foreign Object Detection. In that case, it will continue to heat up, causing the object placed between the charger and the device being charged to become excessively hot and lead to serious injury, as stated above.
So, How Does it Work?
FOD checks for changes in resistance, capacitance, light reflection, weight, and resonance. It also has a metal detector that can recognize the metal object you placed on top of it. Because it would take forever to explain how exactly FOD works for this article. The only thing that matters for the average user is that placing a coin on your wireless charging pad won’t set your house on fire.
You can leave a wireless charger plugged in, but it comes with a risk. Like any other electronic device, a wireless charger can randomly overheat and catch on fire. For extra peace of mind, switch the power off when you’re not at home. Or use something like a Smart Plug to create a daily schedule for the wireless charger.
If your wireless charger is plugged into your computer’s USB port, you can leave it in if the motherboard turns all USB ports off. If it doesn’t, disable USB standby power in the BIOS.
Does a Wireless Charger Waste Power When Not in Use?
A wireless charger wastes very little power when not in use. A wireless charger only draws enough electricity required to sustain an electromagnetic field above the surface to check if there’s a compatible device. Depending, it can draw less than 0.5 W per hour, which is about the same as a wired charger.
Qi wireless chargers can be rated at a standby power that’s less than 10 mW. That’s a hundredth of a Watt. After some back of the napkin math, that’s about 87.6 W annually. So, your wireless charger on standby wastes a negligible amount of power.
On the other side is the overall effect of wireless charger power waste when charging a wireless device. Wireless chargers are not classified as “green electronics” yet, and they are far from it in some cases, which we’ll discuss later. Wired chargers may draw slightly more power than wireless chargers when not in use, but any difference is negligible.
Consider conserving energy on power-hungry home appliances if you’re concerned about your power usage. Examples include your washing machine, HVAC system, dishwasher, and tumble dryer. Of course, you should still unplug your wireless charger if safety is your primary concern.
Is Wireless Charing Power-Efficient?
Wireless charging is significantly less power-efficient compared to wired charging. The coils in a wireless charger and phone lose a lot of electricity in the form of heat, especially if they’re not perfectly aligned. An average charging pad draws about 30 – 50% more power than a wired charger.
Eric Ravenscraft tested wireless and wired charging side by side in 2020. They found that wireless charging uses an average of 47% more power to charge a battery fully. That isn’t a lot of waste for an individual. But on a global scale, it could waste millions of kWh if we all switched to contemporary wireless charging.
It comes as no surprise that a lot of the power is wasted in the form of heat. After all, it’s formerly known as “inductive charging.” A wireless charging pad isn’t all that different from an induction stovetop.
The copper coil in the charger uses electromagnetic induction to transfer power to the coil in your phone. Induction is the most efficient way to transfer heat from your stovetop to a pan. But transferring electricity is different. According to a paper on electromagnetic power transmission, their tests showed a maximum efficiency rate of 90.8%.
Alternative View of Waste in Charging Devices Like Smartphones
Despite the inefficiency of current wireless charging technology, using a wireless charger that you already bought will likely leave a smaller carbon footprint instead of throwing it away.
There are, of course, also alternative views on the inefficiency and the efficiency of making charging cables for phones and the energy used in that process. There is also the issue of charging port wear and trading your phone in or throwing it away because the charging cable doesn’t work anymore.
Eric Ravenscraft’s observation is an excellent point and justified as he asserts that we will need more power plants as wireless charging technology increases in use. This thought process needs to be weighed against manufacturing more smartphones and charging cables due to wear.
When we look at the natural resources required for smartphone and charging cable manufacturing and replacement, it most likely outweighs the energy use of wireless chargers. Future wireless charging technology will also get better with time and investment, and please look at our article on Green Technology, and you be the judge.
Wireless vs. Wired Charger
We can’t talk about wireless chargers without acknowledging the old-school wired chargers. Let’s look at a few notable differences and similarities between the two.
Wireless Chargers Are More Convenient
You’ve probably bought a wireless charger so that you don’t have to deal with cables. Plugging and unplugging a USB connector multiple times a day is unintuitive and could damage the USB port.
Most importantly – you never have to worry about charging your phone with a wireless charging pad. You just plop the phone on the pad or stand, and it charges automatically.
A couple of charging pads in your house and one on your work desk are enough to keep your mind off the battery level for good.
Wired Chargers Charge Faster and Waste Less Electricity
One of the main gripes with wireless chargers is that they are slow and inefficient. Although fast wireless charging standards exist, they’re often twice or even three times slower than a wired charger.
That’s mostly because of the high inefficiency of induction. If a charging pad goes above a certain threshold, it could overheat and damage your phone or catch on fire. Although a wired charger loses some electricity as heat, too, it’s far more efficient. The power goes from the outlet directly into your phone.
In a world where 120 W charging bricks exist, it’s hard for a little 15 W wireless charger to keep up. Especially when half of that is lost to heat.
Both Wireless and Wired Should Be Unplugged When Not in Use
Despite their differences, both charger types benefit from being unplugged when you’re not using them. By sacrificing your convenience, you’ll significantly extend the lifespan of the capacitors, transistors, and transformers found in wired and wireless chargers.
These components are the reason why you hear a buzzing sound when you put your ear on your charger. They always hold a small charge when plugged in, which can turn into a fire hazard.
Please see some of our other interesting articles on Wireless Charging, like “7 Questions About Wireless Charging With A Thick Smartphone Case” and “The Secret to Good Wireless Chargers: Amount of Coils.”
Electrical Small Apliance and Wireless Charging Device Safety
The U.S. Consumer Product Safety Commission (CPSC) recommends unplugging electrical devices when not in use in their Home Electrical Safety Checklist.
The CPSC Home Electrical Safety Checklist states that “Every year, electrical products are associated with injuries, deaths, and fires in homes.” It also specifies in the kitchen, unplugging all countertop appliances, and in the bathroom unplug all small appliances when not in use.
Unplug all small appliances when not in use. Even when turned off, plugged-in electrical appliances may cause a shock hazard if they fall into water.U.S. Consumer Product Safety Commission (CPSC) Home Electrical Safety Checklist
On FEMA’s Electrical Fire Safety Handout it is recommended that you “Unplug small appliances when you are not using them.”U.S. Fire Administration FEMA’s Electrical Fire Safety Handout
Technically speaking, you should keep your wireless charger unplugged whenever you’re not using it. However, keeping it plugged in intermittently for convenience isn’t a huge risk either.
Foreign object detection technology will prevent the charger from overheating if something lands on top of it. Moreover, wireless chargers draw a negligible amount of electricity in standby mode.
- Wikipedia: Qi (standard)
- Qi Wireless Charging: All Phones With Wireless Charging – Qi-Enabled Phones & Compatible Devices 2021
- Spark Connected: What is Foreign Object Detection in Wireless Charging, Anyway?
- Biostar: FAQ: How to turn off USB 3.0’s stand-by power on TH67XE motherboard?
- CPSC: Towsleys Recalls 3-in-1 Qi Wireless Chargers, Power Banks, and Travel Chargers Due to Fire Hazard
- Digi-key: One-Chip Qi Wireless Charging Transmitter
- Debugger Medium: Wireless Charging Is a Disaster Waiting to Happen
- Wikipedia: Inductive charging
- IEEE Xplore: Optimal Design of Electromagnetic Induction High-efficiency Wireless Power Transmission System
- WO2013036947A2 – Foreign object detection in wireless energy transfer systems – Google Patents