Here's how Android makers can balance 120Hz screens and battery life

OnePlus 7 Pro
OnePlus 7 Pro (Image credit: Harish Jonnalagadda / Android Central)

In 2020, phone makers will be offering displays with 120Hz (and even 144Hz) refresh rates. Right now, everyone is certain the new OnePlus 8 and Samsung Galaxy S20 will be packing these 120Hz displays and we should expect to see most every other company which manufacturers phones follow suit with high-refresh-rate screens.

The trend has already begun, and you can buy a phone with a 90Hz refresh instead of the "standard" 60Hz. The benefits are easy to see when you first use something like the OnePlus 7 Pro or a Pixel 4 and notice how much smoother everything looks and how much faster animations seem. But there are drawbacks, too, and the biggest worry is the hit this has on battery life.

More: After trying a 90Hz display I don't ever want to go back

Right now, you can turn off high-refresh rates and go back to the default 60Hz if battery life is a concern, but there should be a more elegant solution. Manufacturers employ some of the best and brightest when it comes to making the phones we love, so let's look and see what might be able to work to strike a balance between ultra-high refresh rates and battery life.

What is refresh rate, and why is 120 better than 60?

The refresh rate is defined as the number in one second that a display updates its image using data from what's called a frame buffer. It's not the same thing as frame rate, which is how many times per second that new data is added to the frame buffer.

Display refresh rate is tied to, but not the same as, frames per second. It's complicated.

The frame buffer is where the data that tells the hardware what to draw on the screen is stored. If data is added to the frame buffer faster than the display's refresh rate can draw it on the screen, things look choppy. If the refresh rate can draw on the screen faster than the data is added to the frame buffer, everything looks more smooth because even if none of the data is new, it is still drawn.

Source: NVIDIA (Image credit: Source: NVIDIA)

It's a tough concept to grasp without a visual. Thankfully, it becomes much easier when there is a visual. In the image above, we see a 60Hz display compared to a 240Hz display. While no phone maker is planning to release a 240 Hz display (yet), the concept is the same. A display with a 120Hz refresh will draw the green ball twice as often as one with a 60Hz display and the animation will appear smoother because the image refreshes twice as fast.

Of course, drawing twice as often means the power used to draw the image is now doubled, too.

More: Samsung's 240Hz Gaming Monitor is the best I've ever used

How much battery does it take?

Front of the Google Pixel 4 XL

Source: Joe Maring / Android Central (Image credit: Source: Joe Maring / Android Central)

That depends on who you ask.

I'm sure a technician with the correct tools could give an exact measurement of how much extra power is used with a high-refresh screen compared to a standard refresh one, but most smartphone users don't walk around with an oscilloscope and current meter in their pocket, so anecdotal evidence is all we can go by.

Measuring smartphone battery life is an exercise in futility because conditions are never going to be the same.

Some users claim the 90Hz setting on the OnePlus 7 Pro, for example, really cuts into their battery life. Others barely see a difference. While that's not helpful at first glance, it does tell us one thing: drawing from the frame buffer to the display doesn't use a lot of battery in the first place.

Discrepancies in battery life during daily usage are nothing new. There are also plenty of factors that play a major part in how long your battery will last, such as network quality, Bluetooth and Wi-Fi usage, actual phone calls, and how many times you check Facebook Messenger.

I found the OnePlus 7 Pro to use 25% more battery at 90Hz.

My anecdotal evidence from testing done in airplane mode by a friend with a 7 Pro shows 90Hz using about 25% more battery than 60Hz with the display in QHD mode. Your anecdotal evidence could be wildly different.

What we do know is that battery life was enough of a concern that Google automatically throttles the 90Hz refresh based on brightness and disables it when the display is dimmer and you won't notice the difference as much. And that it is still working on striking the right balance.

What are the options?

That's the real question. If a manufacturer sells a phone with a 120Hz display and your battery dies in mere hours when you use it, that's not a good experience. That means something has to be done to mitigate the extra load.

A phone maker could just go with the toggle as OnePlus does. If you want that silky smoothness that comes with a 120Hz display, you can turn it on and know that your battery life will suffer. It's an option that a lot of people would gladly accept even if they know it means more time on the charger.

A toggle in the settings or quick settings works but isn't very pretty.

If you're in a setting where battery life is more important, you could turn it off — like when your driving all day or flying somewhere. It's not elegant, but it works.

Another option is to figure out how to turn things on and off dynamically like Google is trying with the Pixel 4. There are benefits and drawbacks to eye health (based on flickering at rates we don't perceive but is still there), and of course, the battery life hit when you upgrade to 90Hz. On the Pixel 4, Google is trying to manipulate when and how that happens based on brightness of the screen.

More: Pixel 4's 90Hz display gets fewer limitations with November security patch

The problem here is that it's a long tedious process to find the perfect settings. Those settings will never be perfect for everyone, so a toggle still needs to be in place. Sometimes, making the machine smart isn't the easy way or the right way.

In the end, this is what will probably have to happen though. A setting will be added to the Android code that gives manufacturers the flexibility to make changes on the fly and some companies will do better at it than others. That's not all that needs to be changed in Android, though.

Android itself needs changes to display animations, too.

Almost everything you do on your phone has some sort of animation attached to it. Those animations were perfected to run at 60 FPS (Frames Per Second, as in how fast the data is written to the framebuffer) and displayed on a 60Hz display. With the advent of screens with a faster refresh, more work can be done here to edit those animations. Right now, 90Hz screens are drawing the same frame of an animation 30% of the time and animations need to be restricted to 60 FPS so that they aren't choppy. Scrolling and animations in Google's own apps need to have some sort of dynamic fix to make things better for better displays.

As long as nobody forces us to lock vsync to prevent screen tearing, I say bring on those high-speed display panels!

Jerry Hildenbrand
Senior Editor — Google Ecosystem

Jerry is an amateur woodworker and struggling shade tree mechanic. There's nothing he can't take apart, but many things he can't reassemble. You'll find him writing and speaking his loud opinion on Android Central and occasionally on Twitter.

  • On my ROG2 phone that has 60/90/120hz options, I use the Armory Crate (which is the gaming hub for the phone that allows the user to tweak phone settings for certain games to favor performance or efficiency) and I add non-game apps that I know I use with the screen on for long periods of time but don't necessarily scroll or look at the screen or care about high refresh rates. By adding the apps to the Armory Crate I can tell the phone to switch to 60hz while in that app, and upon leaving the app, the phone knows to switch back to my previous setting (usually 120 hz). I imagine it helps out battery performance a bit, but probably not by 25%. I have a hard time believing that going from 60hz to 90hz would yield a 25% improvement in battery life. I feel like this would have more of an impact like what you would see in your gas mileage between driving with your headlights off all of the time vs on all the time... Pretty much imperceptible. But even driving with your Air Conditioning on all the time vs never isn't ever really more than a 10% difference in gas mileage, so I have a hard time getting behind the idea that screen refresh rate doubling would impact overall performance of a phone by 25%. If going from 60 to 90hz improves battery by 25% then could we assume an extrapolation that 60 to 120hz under the same conditions tested would show a 50% battery imrovement? If so, I have a hard time believing the ROG2 would get close to 15 hours of screen on time per charge.
  • The thing is, the screen itself is one of the biggest battery drains on a smartphone, and asking it to do its job 30 times more per second has more impact than a car's headlights which have an insignificant impact on a 300 or 400 hp engine.
  • Valid point. I'll have to try a couple weeks at just 60hz and compare my screen on time data vs battery data.
  • Looking into it more on my phone, which has this thing called Game Genie which shows the user what the temperature and battery level of the device is also shows the instantaneous screen refresh rate. From what I can tell, the frame refresh rate is actually dynamic. If you are reading something on the screen or typing, the frame rate is showing 2-10 fps, then when scrolling the frame rate jumps to 120... Just normal phone use will be different than playing a game with high refresh rate graphics and I imagine that one WOULD see a significant battery difference in playing a game for 3 hours at 60 hz vs 120 hz. This 25% difference very well could be true with respect to pure gaming, but if the phone manufacturer makes the frame refresh rate dynamic (jumping up only when needed), for normal daily use, I don't see a 25% difference in battery performance.
  • Hmm, dynamic refresh rate. That's a lot smarter than Google's "sometimes on, mostly off" toggling.
  • This is making the 90 Hz on the Pixel 4 look conservative. Just a couple months ago 90 Hz was cutting edge sorta.
  • As long as battery life is a concern, I'll keep mine on 60hz. Maybe if they make advancements in battery life so phones get 2 days per charge with heavy use I'll use some of that extra battery for smooth animations.
  • I get 2-3 days before charging the ROG2, and it's on 120hz most of the time (total of 8-10 hrs screen on time) I unplugged my phone from a full charge Monday afternoon, it's now Wednesday at lunch time and I have 42% battery left at 6hrs 40min of screen on time.
  • Funny thing is, if you give a 90hz screen phone to someone who is not a techie or nerd, they can't tell the difference.
    I can, but the thing is; it's a bloody phone and I don't need a 500hz refresh rate. I understand it's a balance, and I'm not going to cringe because I missed something that was on my screen shorter than 1/60th than a second. My phone is buttery smooth at 60hz, lasts all day (often two), and is faster than the Pixel 4 anyways. I spent 12 hours a few days ago on a photo documentation project, took almost 200 photos, all with forced flash, and went home with the phone battery at 54%. Not once did I think about refresh rates, but you know that's going to be the next marketing numbers game, anyways. On a dedicated gaming machine, it's worth it, but on normal phones, it's questionable. I actually do more gaming on my phone than some who have gaming phones, and I never find myself wishing for higher refresh rates.
  • Some people don't mind watching DVDs or listening to 98kbps music either. It's a crappy way to experience the art that was produced at a much higher level. If all you want is to get the job done, more power to you. Some people enjoy live concerts and ultra high definition movie theaters.
  • Music I do at the highest quality available, and I can't even listen on an iPhone! Cinema films are at 24fps, although I prefer 4k at 60fps for editing purposes. But what I'm looking at is that, for example; this page I'm typing on doesn't need to be refreshed 120 times per second. Even on movies it's a bit of a waste. If it's sole purpose is so people can brag "Look how smooth my screen scrolls!", followed by "Can I borrow your charger?", I'd rather have the phone with better battery life.
  • That's what I was getting at with my other comment from this morning. Just because the phone is set to 120 hz doesn't mean it's forcing the screen to refresh at 120hz all the time no matter what. It will only spike up to 120 when needed. I was going to add that most games only have 60hz support anyway, so really this whole argument that 120hz is going to drain your battery more than just setting it to 60hz all the time is rubbish. I'd be willing to bet that if you were to log the refresh rate on a 120 hz phone, this histogram would show maybe 5% of the time that the screen is actually refreshing at that rate. Not enough to warrant worrying about battery impact.
  • If you want to watch movies or listen to music at a high definition, then don’t use a phone for that.
  • That wasn't my point. My point was some people choose to experience things at a higher level or quality. Others don't mind just getting the job done. Some people want to have a refined experience on their phone, and if 120hz gives them that refined experience then it will be worth it to them. For those people that still use their phones to make calls and text for the majority of their usage, then 120hz is a waste.
  • Mr. Segundus - Movies I agree with, but more for the size than the resolution. Music though, has changed, and it's to the point where my favorite Sennheiser open backs fed from a million dollar recording studio console, don't sound as good as HTC USonic headphones. And that, I know from personal experience.
  • I think it's obvious when Android OEMs need to do to balance battery and the 120hz refresh rate, and that's add a bigger battery to account for the extra power consumption that a 120hz display like Asus did, and while I think the ROG Phone 2 is extremely overrated, adding a huge 6000mAh battery to account for the 120hz display was the one thing that Asus got right.
  • @Jerry It doesn't look like you touched on the dynamic control of screen refresh rate in the article. On my ROG2 the on-display Game Genie reports the real-time refresh rate of the screen, and it only jumps up to 120 when actually scrolling in any given app. Even most video and gaming apps top out at 60hz when 120 hz is selected in the device. What are your thoughts with dynamic control of refresh rate and how that relates to battery usage?
  • Funny, cause phonebuff on YouTube tested 2 phones, one at 60hz and at 90hz ran it thru the same battery testing and it came back negligible difference in battery life. I think it was 1% difference.
  • High refresh rate is unimportant to me since I don't play games or watch movies. Battery life is and I have my one plus 7t at 60 fps. Funny how with all new phone advancements the negative aspect is the impact on battery life. Bring back removable batteries! I feel phone companies purposely don't want this feature because users will end up holding on to phones way longer, thus impacting future sales.
  • 120hz has no affect on games (unless you're playing one of the handful of games that support 120hz) or video watching. Really the only time 120 hz is noticable is when scrolling through content or navigating on the phone. These instances don't make up a majority of the phone usage and therefore won't have noticable impact on the battery.
  • I read somewhere iPad pro does the same dance. They have a variable refresh rate, and maybe using the new  watch ultra low refresh rate there is a way to get to 120hz without impacting too much battery. I think the iPad is like the Asus, in real time. They will slow down to 60 for videos or even match the frame rate of the video down to 24. And if you have a video on one side and a website on the other side there is a split in refresh rate, can’t remember exactly. However the screen touch latency is always 120. Or just do what Asus did 6000mah, problem solved.
  • 120Hz refresh rate is unnecessary on a freaking phone. It’s overkill. Battery technology hasn’t improved in years. Don’t add 120Hz refresh until battery tech improves dramatically.