XPS 15 9570 4k used in 1080p, battery life ?

Hello,

I'm willing to buy a XPS 15, and the battery factor is very important for me.

I'm curious to see if their is a signifcant difference between the 4k screen with the 4k resolution, and the 4k screen with the 1080p resolution. I don't need a 4k resolution, but i would like to have a tactile screen. It could be a good compromise, if the battery duration have a significant difference.

Is someone using it like this, and could tell the difference in the battery runtime between this two utilisations ?

 

Sadly I don't think there is a difference in battery life, at least meaningful. I've heard people say there is but when asked to run tests I never hear a response. I'd be interested if someone ran this with say a meaningful bench like PCMark8's battery life test, but that request may go un-answered. I've tried to search but didn't find anything solid on this, perhaps someone has better evidence on this? Maybe an online article on a different laptop.

 

I have the XPS 15 w/ the 4K display and I can confirm it WON'T work, or at least as you expect.

I was in the same situation as you, I didn't really need the 4K display but needed the Touchscreen, so I went for it.
Then my 200 IQ mind went like; Of course, If I turn out the resolution to 1080p it will for sure save battery life as much as having a 1080p screen.

Well, in reality, the panel is still a 4K panel and therefore is pushing all the pixels no matter the resolution that you set it to. The only real benefit would be in the GPU part, as in this case, the GPU would just render the 1080p image and not the 4K image which does same some battery life.
In summary, If you really like the XPS 15 and need the touch functionality, go for it, but don't expect the "battery boost" of changing the resolution. From my testing, it will give you 15 extra minutes on non-intensive GPU task and up to 1:30 h when you are using the GPU, especially the GTX 1050. But If you are going to game I'm pretty sure you will be charging.

 

For what it is worth, you can see a small difference in performance when switching from 4K to 1080p. For example, when purposely scrolling up and down a website in Chrome in 4K, I see about 20-25% iGPU usage. When lowering to 1080p and doing the same task, it drops to about 13-18% usage. So there are some savings. The same happens when gaming. When gaming on 4K (with the dGPU active), the iGPU shows about 20% usage (this is purely processing the frames from the dGPU and displaying them). When gaming on 1080p, this lowers to roughly 5-10%.

So when redrawing the entire screen, you do see some savings due to lower resolution. But realistically, you aren't redrawing the screen at all times. When you are in Word or reading a website, the screen is mostly static and in both cases the iGPU drops to idle usage: 0-1%. And no savings happen there at all. So it is not worth it to switch to blurry resolutions over a 4K resolution.

Your battery life is also heavily dependent on whatever it is you are doing. I can easily get 7 hours on my 2 year old 9560, with a 4K panel. And if I stretch it by doing very minimal things (mostly note taking, lowest brightness), I can get over 8 hours.