Having an extra monitor can be very handful, especially if you use your laptop for work. You can do one task on a laptop screen and do web browsing on your external monitor. For instance, I’m using a laptop screen for writing and a 27-inch monitor for research (web-browsing, watching Youtube videos, etc.)
However, will connect an external monitor slows down your laptop?
After some testing and research, I came to the following conclusion:
Whether or not an external monitor slows down a laptop depends on how you use the monitor. For instance, it will not slow down your laptop if you mirror the screen. On the other side, it can slow down a laptop if a monitor is used as a separate screen.
Ok, you have a nice short answer, but there is so much more to this. Keep reading and find out whether or not it is a good idea to connect a monitor to your laptop and how it ACTUALLY affects the laptop’s performance.
Let’s dive in!
Is it bad to connect a laptop to the monitor?
Let’s start with safety first. Many people are wondering about the idea of connecting a monitor to their laptop. But should they be?
Connecting a laptop to the monitor is not bad because monitors are independently powered. Instead, they just pass the video signal. Also, modern laptops are designed to run with several external monitors. The only risk of damage is if the monitor has some electrical problem.
Note that the manufacturer would not have equipped a laptop with some type of video port for nothing. It obviously serves its purpose. Also, video out ports are designed for full-time use and will not induce damage under standard conditions. If connecting a monitor to laptops would produce some kind of damage, the shops would be full of damaged laptops to be repaired at the manufacturer’s expense if still in warranty.
Moving on.
Does connecting a monitor affect laptop performance?
Now let’s see whether connecting an external monitor affects the laptop’s performance. We will first start with the overall performance. For instance, does it slow down your laptop overall?
External monitor effect on overall performance
Do you recall the parallel resistor configuration you learned at school?
Why does adding more resistors result in decreased total equivalent resistance?
It is because every resistor in parallel configuration has the same voltage. This means every resistor enjoys current the same way as if you configure each resistor in its own series circuit. This means adding more resistors in parallel means more current. More current in the same voltage means lower total equivalent resistance.
What does it have to do with monitors and laptops? Good question.
Connecting an HDMI cable to your laptop is just like adding more resistors to the parallel circuit since its inside works the same way. The output simply splits.
However, note that the current doesn’t split. The parallel circuits add more current to the new HDMI you’ve attached. This also means no power loss, and the system remained stable.
However, this only applies if you put your screen mode to Second Screen Only, which you plan to do, and Duplicate.
On the other hand, using the mode Extend does affect performance since the laptop has to render on both screens. In that case, it may result in some performance loss.
Also, dont forget that screen resolution affects the laptop’s performance. That GPU will support the higher resolution. It will have to work a bit harder to do so. However, since most of the increased work will be going on in the GPU (as opposed to the laptop’s CPU) and at a rate that it can support anyway, you should not see any significant degradation in the performance of the laptop for anything else which might be going on.
However, note that the work involved in editing videos does not lie so much in what it takes to display them. It is CPU intensive in a way that does depend on the resolution of the video, but not on that of the monitor.
If the laptop comes with a dedicated GPU inside it, the chances are high that your HDMI port is connected to the GPU. In this case, your laptop would not become slower.
On the other side, if you have a laptop without a dedicated GPU (Intel HD graphics, for instance), your laptop can become a bit slower, but not to a higher degree. This is due to your integrated graphics chip would now need to drive two screens (monitor and your laptop screen)
Note that if you use both monitors at the same time, there will undoubtedly be an extra load on the system. However, this should not prevent you from trying so. It is doubtful to cause a performance loss unless you are trying to do something which is GPU intensive on both screens simultaneously.
However, as long as you don’t play full-screen games on both monitors, the impact is minor to nearly zero.
CPU usage test
The purpose of this test was to compare CPU usage with a connected monitor and without one. The testing method was actually very simple. I did basic web browsing in both scenarios.
Web browsing without an external monitor
Web browsing with an external monitor
Final comparison
The amount of CPU power required for monitors isn’t related to the number of monitors. Instead, it’s related to how many tasks are opened on the laptop.
Just displaying an empty screen consumes very little computing power – the graphics card will just run through the image memory and cast again and again without concerning the CPU.
Showing a movie on display means decoding each new frame of the movie. Playing a game means computing the scene, rendering the scene, and displaying it.
So “how much more does it require” isn’t a suitable question.
Having 2 monitors running two movies consumes twice as much power as playing 1 movie on one monitor, obviously. Having 2 monitors showing the same movie by using mirroring draws no extra.
Having 2 monitors and showing the movie on one monitor and playing a game on the other one obviously draws more. Not because you have two of them, but because you are both showing a movie and at the same time playing a game.
To recap this, I will use the following analogy. If you have one additional person at the dinner table, will the food on the table disappear faster or not? Of course, it will.
External monitor effect on gaming performance
Before analyzing the effects on gaming performance, we first have to understand something called Optimus technology.
In simple terms, Optimus is an Nvidia technology where the GPU is connected to the iGPU of your CPU. This way, the iGPU takes all the display load, and the dGPU can relax when on battery. However, this decreases performance a fair bit since the iGPU has to also process all the frames that your GPU has already processed!
So, when you disable Optimus, the display is now connected to the NVidia dGPU, and so, the processing overhead of the iGPU is cut down, and you get more FPS.
BUT, since the GPU is directly connected now, it can’t go to sleep mode to boost the battery.
So, what effect does an external monitor have on laptop’s gaming performance?
An external monitor can increase gaming performance on the laptop due to achieving higher FPS. However, this is only the case if the external monitor hash stronger specs and you are using dGPU.
Most laptop screens are still stuck in 60Hz territory, though you can easily find 100Hz+ monitors today. These will allow you to play at an actual 100fps+ compared to a 60Hz laptop screen.
For instance, if your laptop performs truly well and has the potential to reach an FPS of more than 60, but your laptop screen is only 60Hz, then using an external monitor with a higher refresh rate would be able to display a higher FPS.
Contrary, if your laptop performs lower than 60FPS and your laptop screen is only 60Hz, then using a better external monitor wouldn’t change anything.
Thanks to Jarrods Tech analysis, here are some results in FPS differences in laptop vs external screen:
If the full analysis, we can see that in ALL games, the external monitor wins.
Why does my laptop slow down when connected to an external
monitor?
From my experience, there could be many reasons; however, I will list the few common ones, although most of them we already partly covered.
Optimus technology is enabled
When Optimus is enabled, your laptop is using an integrated GPU instead of a dedicated one. To learn how to disable it, check this article.
You are using the monitor in Extended mode
There is a difference in terms of computer load between using your external monitor in mirror mode or extended mode. With mirror mode, you are just duplicating the laptop screen. On the other side, when you choose an extended mode, you are running two screens.
To solve this, either choose mirror mode or use just the external monitor and turn off your laptop screen.
Do external monitors use up RAM?
External monitors don’t use up more RAM per se. The only thing way it can use up more RAM is if you are running two separate tasks on each monitor.
For instance, on a laptop screen, you are web browsing while on the monitor, you are playing games.
Recommended reading:
Overclocking Laptop Monitor (All You Need to Know)