Is Bluetooth draining the battery? All wireless technologies require electricity, but how much is a subject full of anecdotes and theories. Despite the advancements in Bluetooth technology, there is still a widespread belief that turning off Bluetooth, Wi-Fi, NFC, and various other technologies when you are not using them can bring a lot more life to your phone.
I find these old habits difficult to break. Yes, I still turn off Wi-Fi when I leave the house and turn off Bluetooth until I hear music. But is that necessary in the modern age of "intelligent" technology? How much battery will I waste if I leave bluetooth on while not using it? What about music over bluetooth? Is the battery consumption higher than when using speakers or wired headphones? To find the answers to these questions, we grabbed a handful of phones and ran some tests.
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How we tested
To understand exactly how the use of Bluetooth affects battery life, we have selected five different smartphones as of 2020. In this test we have the Samsung Galaxy S20 Plus, the Huawei P40 Pro, the ZTE Axon 11, the Xiaomi Poco F2 Pro and the Realme X3 Superzoom. We went through two unique scenarios each and monitored the results with our internal test software.
The first is a typical daily battery discharge scenario that is used to determine whether turning off Bluetooth actually saves battery. For this purpose we carried out two series of tests. One test with bluetooth off and another with bluetooth on but idle - i.e. not connected to anything - to compare results. The test itself consists of three cycles. The first is 90 minutes of web surfing, followed by 90 minutes of sleep and another 90 minutes of surfing. The phones then sleep for 16 hours on the second cycle to get a good overview of the power consumption when idle. The third cycle repeats the first cycle.
We ran five phones through two unique test scenarios.
The second set of tests simulates a more demanding Bluetooth-specific use case and should determine how much Bluetooth affects battery life when you actively use it. To simulate this, we monitored the video playback for 4 hours like you could on a long flight. This series consists of a control test with bluetooth off, bluetooth on but no connection, and finally the video audio over bluetooth using the basic SBC audio codec.
We set each display brightness to 200 nits to keep the tests fair. All of these tests also turned off cellular data, NFC, and everything else on each handset. With the exception that Wi-Fi remains enabled in the first scenario so that we can surf the Internet.
We also used averages of the results to get a better view of Bluetooth battery usage. All of the graphs in this article are based on an average based on testing with the five devices above.
So ... does turning off Bluetooth save battery power?
No not true.
During our 26-hour "typical day test", turning on Bluetooth only consumed 1.8% more battery than the test with Bluetooth turned off. On average, during this test, our devices used 49.4% of their battery with Bluetooth turned off versus 51.2% with Bluetooth turned on. When extrapolated to a full charge cycle, Bluetooth typically uses less than 4% additional battery life. Disabling this option can add 10 to 15 minutes of extra time for a device that typically has five hours of screen on time. Peanuts really.
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There was a slight difference between the devices we tested. The Huawei P40 Pro and Poco F2 Pro saw the biggest difference in turning Bluetooth on and off - a 3% difference. Meanwhile, the Samsung Galaxy S20 and Realme Superzoom recorded a slightly lower power consumption with Bluetooth switched on. This is likely due to an error rate that shows how little impact Bluetooth actually has on battery life.
For a more detailed breakdown, see the graphic below:
What stands out here is that the idle battery is essentially the same over a 16 hour sleep period. We can calculate the difference of 0.2% up to an error rate - regardless of whether Bluetooth is activated or deactivated. During our four-hour, 30-minute cycle of use, our devices showed, on average, a fairly constant 1% difference in battery usage. Again, this is so small that it makes practically no difference to battery life.
Bluetooth radios are turned off while the phone is asleep, which reduces battery consumption.
This underscores that modern smartphones put Bluetooth radios to sleep when they are not in use. You're just awake and regularly checking for pairable devices while your smartphone is awake. So, you really don't have to worry about turning off bluetooth before going to bed.
How much battery does Bluetooth use?
So Bluetooth doesn't really affect the battery if it is left on but not used. What if you are actively using bluetooth on your phone? Our four hour video playback test shows a similar difference in battery drain on all five devices.
The comparison between Bluetooth off and on but not connected shows an average battery consumption of only 1.6% over a period of four hours. This is still very small, but shows more power consumption than our previous test. Probably because our devices are used continuously for extended periods of time, so the Bluetooth radios spend less time sleeping.
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Extrapolated to a full charge cycle, watching videos with Bluetooth switched on but without a connection increases power consumption by an average of 6.6 percent. It's still pretty small, but nothing. However, this constant video playback scenario is highly unlikely in the real world.
Interestingly, there are quite a few differences between different smartphones. The Samsung Galaxy S20 Plus achieved exactly the same result with Bluetooth switched on and off. Meanwhile, the Realme X3 Superzoom is hardest hit as it has an additional 4% battery drain over four hours.
The reason for this discrepancy is likely to be found in the optimization of the smartphone's hardware and software. The Exynos chips on the Galaxy S20 Plus and the Kirin chips on the Huawei P40 Pro use different radios than the Snapdragon SoCs on the other phones. Similarly, each Android software variant will likely have different algorithms for waking up and pairing Bluetooth scan intervals. No two devices will see the exact same amount of battery discharge, but the results will vary from zero to negligible in either case.
See also: How to extend the battery life of your Android phone
Does using Bluetooth headphones drain the battery?
This is a very good question, and the reason why we ran these second tests with audio playback as the base use case. After all, that's what most people use for bluetooth these days.
The results show that playing audio through Bluetooth uses essentially the same amount of power as playing audio through speakers or headphones with Bluetooth turned off. On average, our devices only recorded a 0.2% increase in power consumption when playing audio via Bluetooth. So far into the fault area. The Galaxy S20 Plus and the Poco F2 Pro showed no noticeable difference in battery consumption over a listening period of four hours.
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The reason for this is that Bluetooth audio coding algorithms on digital signal processors (DSP) in modern smartphones run efficiently and use very little power. At the same time, audio amplifier circuits are turned off when audio is played via Bluetooth. This offsets the power consumption of the Bluetooth radio chip. The louder you listen, the greater this energy saving will be.
What we learned
Our test is just as accurate and doesn't consider every possible Bluetooth use case. That said, it gives us a good look at how Bluetooth affects battery life from an overall perspective. There are small differences in battery discharge between idling the smartphone and turning the screen on, but we're only talking about minutes of difference between on and off.
It is important that Bluetooth does not affect the battery life when idle. As a result, the battery will not discharge if it is inactive for a long period or if it is switched on accidentally overnight.
The vast majority of users will not experience any noticeable extra battery drain if they forget to turn off Bluetooth. Turning it off is still a good idea to avoid connecting to unwanted devices and if you are very concerned about security.
To answer our question about the title, Bluetooth drains your smartphone's battery very little. You really don't need to worry.
