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Asus Zenfone 8 Battery test: Good night power management

This device has been retested in the latest version of our protocol. Overall, sub-scores and attributes are up to date. For detailed information, check the What’s New article

The Asus Zenfone 8 made its appearance in May 2021. Packed with features, it belongs to our Premium ($600-$799) segment. Let’s take a look at some of its key battery test results.

Key specifications:

  • Battery capacity: 4000 mAh
  • 30W charger
  • 5.9-inch, 1080 x 2400, 120 Hz OLED display
  • Qualcomm Snapdragon 888 5G chipset
  • Tested ROM / RAM combination: 128 GB + 8 GB

About DXOMARK Battery tests: For scoring and analysis in our smartphone battery reviews, DXOMARK engineers perform a variety of objective tests over a week-long period both indoors and outdoors. This article highlights the most important results of our testing. (See our introductory and how we test articles for more details about our smartphone Battery protocol.)

Test summary


Sub-scores and attributes included in the calculations of the global score.

Asus Zenfone 8














Key performances

Charging Time
1 day 21h
Battery life
Charging Time
80% Charging time
Charging Time
Full charging time
Quick Boost
3h08 autonomy
after 5-minute charge
Please be aware that beyond this point, we have not modified the initial test results. While data and products remain fully comparable, you might encounter mentions and references to the previous scores.


  • Good power management at night
  • Charging time from 0% to 80% is acceptable in its segment
  • Residual power drain kept under control


  • No wireless charger
  • Disappointing in music and video streaming
  • Performance in on the go tests, especially for calling and camera

Despite having specs that are similar to its competitors in this review, the Asus Zenfone 8 lags a bit behind in most tested categories.

We compared the Asus Zenfone 8’s performance with two other devices in our Premium segment, the OnePlus 9 and the Samsung Galaxy S21 5G (Snapdragon); battery capacity, tested charger, display type, and resolution, and processor specifications for all three devices are shown in the table below.

Asus Zenfone 8 OnePlus 9 Samsung Galaxy S21 5G (Snapdragon)
Battery capacity 4000 mAh 4500 mAh 4000 mAh






25W (not included)


Display type OLED OLED OLED
Display resolution 1080 x 2400 10800 x 2400 1080 x 2400
Chipset Qualcomm Snapdragon 888 5G Qualcomm Snapdragon 888 5G Qualcomm Snapdragon 888 5G

Autonomy (51)

How long a battery charge lasts depends not only on battery capacity but also on other aspects of the phone’s hardware and software. The DXOMARK Battery autonomy score is composed of three performance sub-scores: (1) Stationary, (2) On the go, and (3) Calibrated use cases. Each sub-score comprises the results of a comprehensive range of tests for measuring autonomy in all kinds of real-life scenarios. 

Light Usage
Light Usage
Active: 2h30/day
Moderate Usage
Moderate Usage
Active: 4h/day
Intense Usage
Intense Usage
Active: 7h/day

The Asus Zenfone 8 comes in behind its rivals in all three of our autonomy test categories. Further, its battery gauge is not especially accurate, since when the battery gauge shows 20% power remaining, there is really only 17.9% left.


Asus Zenfone 8



Vivo Y72 5G
Best: Vivo Y72 5G (104)

A robot housed in a Faraday cage performs a set of touch-based user actions during what we call our “typical usage scenario” (TUS) — making calls, video streaming, etc. — 4 hours of active use over the course of a 16-hour period, plus 8 hours of “sleep.” The robot repeats this set of actions every day until the device runs out of power. 

The Asus Zenfone 8 lasted 53 hours 37 minutes, which is 3 to 4 hours less than its rivals, but still offers more than 2 days of autonomy. It manages night dischage well, losing only 2%, compared to the OnePlus 9’s loss of 2.33%.

Typical Usage Scenario discharge curves

On the go

Asus Zenfone 8



Samsung Galaxy M51
Best: Samsung Galaxy M51 (96)

Using a smartphone on the go takes a toll on autonomy because of extra “hidden” demands, such as the continuous signaling associated with cellphone network selection, for example. DXOMARK Battery experts take the phone outside and perform a precisely defined set of activities while following the same three-hour travel itinerary for each device.

The Asus battery struggles in on the go tests, especially when calling and using its camera, though it performs almost as well as its rivals for social apps on the go.

Autonomy for on the go use cases (full charge)


Asus Zenfone 8



Samsung Galaxy M51
Best: Samsung Galaxy M51 (100)

For this series of tests, the smartphone returns to the Faraday cage and our robots repeatedly perform actions linked to one specific use case (such as gaming, video streaming, etc.) at a time. Starting from an 80% charge, all devices are tested until they have expended at least 5% of their battery power.

Although the Zenfone 8 is well optimized with its screen off in idle mode, it does not fare well against the competition. All video test cases drain its battery quickly, though it manages to do nearly as well as the OnePlus and Samsung when gaming.

Autonomy for calibrated use cases (full charge)

Charging (75)

The DXOMARK Battery charging score is composed of two sub-scores, Full charge and Quick boost. Full charge tests assess the reliability of the battery power gauge; measure how long it takes to charge a battery from zero to 80% capacity and from 80 to 100%; and measure how long and how much power the battery takes to go from an indicated 100% to an actual full charge. With the phone at different charge levels (20%, 40%, 60%, 80%), Quick boost tests measure the amount of charge the battery receives after being plugged in for 5 minutes. 

in 30 min
0 - 80%
Full charge

Unsurprisingly, the OnePlus 9 with its 65W charger is far ahead of both the Asus and the Samsung in our charging tests.

Power consumption and battery level during full charge

Full charge

Asus Zenfone 8



Black Shark 5 Pro
Best: Black Shark 5 Pro (121)

It takes 1 hour 51 minutes to fully charge the Asus Zenfone 8 with its 30W charger, which is a bit slower than the Samsung Galaxy S21 5G (Snapdragon) with its 25W charger. The difference is that Asus decreases the charging power at around 75% capacity to conserve battery longevity, while the Samsung waits to slow charging until it gets to 87%. The OnePlus 9 takes only 33 minutes 32 seconds to achieve a full charge.

Time to full charge

Quick boost

Asus Zenfone 8



Realme GT Neo 3
Best: Realme GT Neo 3 (111)

The Asus Zenfone 8 provides an average of more than 3 hours of additional autonomy with a five-minute charge. This is better than the Samsung’s 2 hours 34 minutes, but the OnePlus 9 provides a whopping near-7 hours.

Asus Zenfone 8 OnePlus 9 Samsung Galaxy S21 5G (Snapdragon)
Autonomy boost (hh:mm) 20%3:19 8:26 2:38
40%3:17 5:59 2:45
60%2:33 5:28 2:09
80%1:27 4:02 1:57
Percentage boost 20%9.9 %23 %7.4 %
40%9.8 %16.3 %7.7 %
60%7.6 %14.9 %6 %
80%4.4 %11 %5.5 %
Energy consumed 20%1964 mWh4923 mWh1466 mWh
40%1944 mWh3491 mWh1528 mWh
60%1512 mWh3188 mWh1195 mWh
80%864 mWh2354 mWh1088 mWh

Efficiency (75)

The DXOMARK power efficiency score consists of two sub-scores, Charge up and Discharge rate, both of which combine data obtained during robot-based typical usage scenario testing, outdoor mobility testing, charging evaluation, and power measurements, and then take into consideration the device’s battery capacity.

Although the Zenfone 8 just edged out the OnePlus in discharge efficiency, it was quite a ways behind the Samsung, and both the OnePlus and Samsung did better than the Asus device in charge up efficiency.

Charge up

Asus Zenfone 8



Nubia RedMagic 7 Pro
Best: Nubia RedMagic 7 Pro (105)

The Asus Zenfone 8 comes in last among the three devices for charge up and charger efficiency; that said, its charger efficiency is not bad for its segment.


Asus Zenfone 8



Apple iPhone 13 Pro
Best: Apple iPhone 13 Pro (121)

The Zenfone 8 achieves slightly better results than the OnePlus 9 in discharge efficiency, particularly in gaming and video playback. The Samsung is a better-optimized device than either the Asus or the OnePlus.


The Asus Zenfone 8 struggles to provide a good autonomy and charging experience, but does a decent job managing residual power drain and power consumption at night.

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