Does it make any difference in power consumption to run a
game in Windowed mode vs Full Screen?

Does 2 or more Windows open vs only 1 make any difference?

Trying to get more battery life on laptop when anway from the mains / plugin.

Thanks

I'm not an expert but the stuff that would boost power consumption would be the GPU or CPU boosting into higher performance clocks. So I would think if fullscreen and windowed used the same settings, it wouldn't make any difference. If you ran a game at 640x480 in a window though, as opposed to 1280x720 or whatever in fullscreen, then the GPU and CPU would be working less hard and would draw less power.

Full screen is better but you can also turn off the desktop (explorer.exe if you are using Windows). The savings are negligible though on a modern computer. Better turn off things you do not need.

Do you just kill it in Process manager?
it seems like it will kill your game too.

That are many better ways to save your battery: play the game at lower resolution or lower graphical settings or use RivaTuner Statistics Server and limit your in game framerate or do all of the above.

I would not bother with explorer, all the stuff it would use resources for is in the page-file when playing fullscreen, and in windowed it would screw everything up to kill it. Definitely kill every non-essential program though, and make sure your startup list is only stuff you always want running. The less resources your PC is using, the less power it is using. You can use task manager to see what is using CPU/GPU/RAM resources at any time.

Just like I and everyone else said, there are many other places to start looking for savings first. Not worth it to bother with killing explorer and restarting it again. That solution is more for when you are critically low on RAM or it affects the game in a bad way.

Synchronised screen? For some games you can go with a bit lower F/s with no problems so maybe 50Hz & the F/s ceiling the same naturally. Emulated game? Do you really need to emulate more than a certain amount of frames? Do you have buttons to turn things like Bluetooth and WiFi off? Click click! Voice recognition and search on? Click! Many keep so many things running all the time and while it matters little on a desktop it sure does matter on the mobile/laptop.

Does Windows still have that indexing service running all the time? Kill it! It is quite useless unless you have a slow and big spinning hard drive full of documents that you may need to search among and cannot remember their names.

To add to what's been said already (I've been quite interested in energy consumption lately, personal conclusions below but frankly, nothing unexpected except for the absolute randomness of engines optimization):

From what I've gathered testing lots of things with a watt-o-meter on my desktop PC (mostly, on Windows 10) and my laptop (Ubuntu) which is an old gamer laptop with bad energy use, energy consumption easily skyrockets with higher framerates and, to a lesser extent, resolution.

The other settings are really more of a gamble (graphic settings, windowed mode, wrappers, shaders, background apps...). I've found it really depends on the engine optimization here, with 'Ultra' having the worst quality/energy ratio. Some really well optimized games (new and old) are really energy friendly, but badly optimized ones easily add 100W+ without heavy tweaking. Obviously, indies and older games (with FPS capped at max 60fps, otherwise expect bugs and burns!) fare better.

In all cases I've found then, FPS is the first priority, resolution second. Going from 60 to 30 (or 40/45, a great middle ground if you don't mind sync issues) sometimes makes the consumption dip by about 60W, if not more (I've found a case of 80W+ but can't remember the game). Going from 1440p to 1080p yields about 30W. And on a laptop, limiting the framerate helps quite a bit with heating issues.

I've also noticed that Windows 10 has three energy saving modes that work better than I expected (Linux does a good job already, even better with dedicated apps). They seem 'semi-auto': Performance is quite useless, allowing everything to be boosted to max all the time. Balanced is really good and tries to lower things by a margin and max them when needed (per apps). Eco mode does helps depending on the apps: it can really slow Explorer down but not necessarily hamper a game (even something like The Witcher 3), as the system seems to allow ample use of the GPU. But it varies a lot depending on use. Whatever task that isn't working 100% seems to be throttled down. Note that going in the Advanced settings allows you to determine the Min and Max CPU use for each mode, and also the cooling method (Active/passive). I think on a laptop the CPU max usage in Eco mode default to less than 100%?

And finally: monitor brightness. Whatever the use, that thing will eat batteries for breakfast. Lower it! (on a properly calibrated monitor, having a low brightness (about 20%) is totally fine, actually better for graphic tasks and your eyes) It's interesting on desktops too: my 1440p monitor dips to about 25W(20) at low(est) brightness, rather than around 60+ at 70%+ brightness.

=> cap the FPS (VSync or/and tools like Riva Tuner, libstrangle on Linux etc.), resolution (compensate blurriness with centered ratio or shaders if need be), brightness, eco modes, and of course the fewer the tasks, the better. Window/fullscreen doesn't change much if at all. Resolution upscaling (with dgVoodoo) does but less so than native res. change. Don't forget about a neat setting that is beginning to show up here and there: resolution scaling (100% = native), which allows for higher perfs (and energy saving) with lower values, quite like resolution change (down) but smoother (you lower by a percent, not by steps from one res. mode to another).

Nice research! Well done. The brightness is so true. I forgot about it as lowering it to bottom or as low as possible is about the first thing I do on a screen (desktop, laptop and mobile all).

If there's filters, stretching or other, then it will be more expensive to run and fullscreen is probably better.

I would go Full Screen, unless you can't for some reason. Generally lower resolutions aren't supported as much anymore (especially on TV's), so like DosBox you can do a 3x multiplier, taking a 320x200 to 960x600 windowed.

Cool, Thanks for all of the ideas.
Yes, when I set up my laptop,
I stop as many process as possible.

Cortana eats alot of RAM.
It's hard to kill, but you "level up" when successful.

Some of the suggested programs I'm unfamiliar with
I must look them up.

Darucas, what a huge treaure trove of info.

Hope others can also get tips on stretching out the battery life.
There's so much junk running in the background anymore,
it definitely impacts battery life.

Kill process. Try to delete program... fails.
Kill process. Try to delete program... fails.
Kill process. Try to delete program... fails.
Kill process. Try to delete program... Success!

Cortana Gone!

Killing a process doesn't delete a program permanently, just temporarily - from RAM.

You'd think all those characters in zombie movies/series have heard of zombies before and aim for the head. :-P

Yes, which is why you would have the directory open and trying to delete the actual program so when Windows 10 tries to reload it it can't. But you can't delete a locked file (locked because it's loaded or opened by another process). I did the above like 7 times until i managed to get rid of Cortana on a friend's computer.