Whether dual monitor uses more GPU or not depends upon what kind of work you are performing on your PC.
As far as gaming is concerned, according to several tests conducted by users, as well as by myself, there isn’t a whole lot of difference in performance when using a single monitor or two monitors – whereby the second monitor is sitting idle and you game only on your primary monitor.
Of course, if BOTH the monitors are intended for gaming whereby you have an extended two monitor gaming display, than that can take heavy toll on your graphics card as you have potentially increased the amount of pixels the graphics card has to render for the game.
In the article, I will reference three studies, including my personal study, on how much the GPU gets affects when using dual or more monitors.
But TL;DR, the answer to the question “Does dual monitor use more GPU?” is yes BUT the difference is PROFOUNDLY MARGINAL – almost negligible.
More Pixel = More GPU Being Used
So the general idea is that the more pixels you have on your display, the more the GPU has to work.
It does not matter whether your system is sitting idle with a blank Desktop screen open, or whether it is running a AAA game.
If there are pixels, the GPU is at work.
So having two 1920 x 1080 (Full HD) displays means the graphics card has to render twice as many pixels as a single 1920 x 1080 display.
Following this idea, a single 4K Monitors would have four times as much pixels as a single Full HD display. So with a simple math logic you can deduce that technically a single 4K display would require twice as many GPU resources as compared to dual FHD monitors.
The point being made here is that in theory it is the amount of PIXELS your GPU needs to render, not the amount of monitors you have, that dictates how much of its resources have to be used.
Practically though, the difference when using a single Full HD, dual or even triple Full HD displays, has only a little impact in most cases.
How Much GPU is Being Used When PC is Sitting Idle?
You can conduct a simple test yourself using the good old task manager.
With the Task Manager open, head over to the performance tab, and look for the GPU usage as shown below.
If you have two graphics cards, like I do, then you will have both of them listed in the menu. When sitting idle, the integrated graphics card is the one being used.
Therefore, you can check how much a difference in usage two more monitors can have on it.
When idle, there is literally no difference when using single or dual monitors, they both sit at 0%.
Of course, when you perform simple actions like move a window around, open an app, the usage of the GPU will increase, but this increase will be consistent with both single and dual screen setups.
So for basic tasks, you can expect a very small, almost a negligible, difference in performance.
But what about heavier tasks like gaming?
So Does Dual Monitor Use More GPU When Gaming?
Contrary to logic, according to several tests conducted by different users, the impact dual or more monitors have on gaming is very little.
I tested dual monitors on two games: Riftbreaker, and Subnautica
I used MSI Afterburner to record the frames per second and GPU usage in game.
The games were played on an Intel Core i7-7700HQ, with 16 GB of RAM and NVIDIA GTX 1050Ti graphics card.
Important Note: The second monitors is sitting idle! The game were NOT played on extended-display mode. In other words, the games were played on a SINGLE monitor.
Here are the results:
Riftbreaker – Ultra Preset at 1920 x 1080 Resolution
With Riftbreaker there was literally no difference if you have another monitor attached to your PC.
While there are ups and downs in frame rates here and there when gaming, but Riftbreaker in general was hovering at about 41-43 FPS at ultra settings on 1080p resolution in both scenarios.
Subnautica (Moded) – Ultra Preset at 1920 x 1080 Resolution
You can see a similar result with Subnautica.
There is literally no difference in frame rate or in GPU usage for both Intel HD 630 or the GTX 1050Ti if you have another monitor screen connected.
Case Study by HypnotizeD Gaming & Tech
A YouTube user that goes by the name HypnotizeD has done a fairly neat study on whether multiple monitors affect FPS in games.
As expected, the results are in-line with what I tested with my games above.
There is literally no difference in GPU usage when you have two, three or even four monitors connects.
HypnotizeD tested CS:GO, Shadow of the Tomb Raider and Deus Ex: Manking Divided with upto 4 monitors.
Here is a screenshot of the results:
|Number of Monitors||1||2||3||4|
|Deus EX: Mankind Divided||90.1||89.3||88.6||88|
|Shadow of the Tomb Raider||103||103||101.1||98.5|
It can be seen clearly here that having dual monitors does not affect the performance at all.
Having three or four monitors has a slight impact on the performance, but in most cases it is only marginal and would hardly be noticeable.
Case Study by TechTeamGB
A similar test was conducted by TechTeamGB. This study is far more comprehensive whereby they have not only tested several games, but have also tested different graphics card to check if dual monitor affect GPU usage.
But the conclusion of the test is the same. There is very little to NO difference in performance when using a dual monitor while gaming.
So here is the summary. If the second monitor is sitting idle while you game on your primary monitor, then no, dual monitor does NOT seem to use more GPU to the point that it may affect performance.
If you were to GAME ON BOTH monitors, then that is a different story.
How Does Extended Display Gaming on Dual or Multiple Monitors Affect GPU?
If you game on dual monitors, meaning you have an extended gaming display, than that can EAT up your GPU.
With a single Full HD display, for instance, the GPU only has the to render 1920 x 1080 pixels of your game.
If you have dual monitors, it will have to render 3840x x 1080 pixels of the game.
So while a certain graphics card may have no issue running a game at 1920×1080, it may not be able to sustain playable FPS at 3840×1080 resolution.
Do More Monitors Affect FPS?
As tested above and as proven by several case studies, more monitors DO NOT affect FPS IF the game is being played only on a single monitor while the rest sit idle.
Of course if you intended to play your game on one monitor and have something else running on your second display like YouTube or Twitch, then that can affect FPS.
Twitch, or any other streaming service, can literally destroy your frame rate. Twitch streaming encodes your videos. The encoding processes takes up a lot of CPU and GPU resources.
Does Running Video on Second Monitor Affect FPS?
Absolutely, anything that requires the graphics card to kick in, would affect the FPS on your game.
Watching a video requires the graphics card to decode the video. Streaming on twitch requires the graphics card to encode your videos.
With a video running, your graphics card will have to multitask and allocate resources to both task.
Fortunately, the difference watching a video on a second monitor while you play game on the first can make is also quite small.
So the answer to the question “does dual monitor use more GPU?” involves two components: technical and practical.
Technically, having two monitors DOES use more GPU.
Practically though, the difference a second monitor makes is quite negligible in the following scenarios:
- You game on the primary monitor while the second monitor sits idle.
- You are performing every day mundane tasks like watching a video, word processing, surfing the web etc.
In graphically intensive scenarios, however, such as when you have an extended dual monitor gaming display, then yes having dual or more monitors would use more GPU.