[T-Mobile LG V10 General] warBeard_actual:
The maximum percentage or battery life “savable” by doing this type of thing is really going to depend on a lot of variables. In testing, it is most important to first establish a baseline, and a valid method to measure your outputs. A model/example would be: I am going to charge my phone to 100%, have it in airplane mode, and only have these 3 apps installed to run the tests. After I charge it, I am going to leave the display on for an hour straight, without interacting with the device, then let it sleep for 4 hours, wake it back up, open and close app#1 150 times, then let it sleep again, etc… maybe for the sake of merely evaluating CPU usage, you would disable the location, turn off auto brightness and set the display at minimum, all for the sake of creating a repeatable environment each time you make a change and want to measure impact of that change, etc… you see where I am going with this. Removing variables to quantify impact of the changes you made, would be critical.

What I am getting at is I would seriously doubt the number this individual threw out (2%) has any real merit, for several reasons.

The first and foremost reason being is that he probably didn’t run a valid set of tests to come to that number. However, even if he did, the potential to save power becomes greater as hardware becomes more and more efficient through technological advances. Chips are not what they were even a year ago in that aspect. The Snapdragon 820, for example, or some of the newer Exynos chips from Samsung – all of which are using the 14nm finf process – are extremely efficient in power management.

Displays, all of these things – there is more noticeable impact over extended periods of time when you are talking about “trim a little here” “save a little there”.

To put this into a different perspective, but where the principle still applies, you can look at how efficiency of engines (cars) are impacted by drivetrains. Your car has a rated HP, and the translated power to the ground is some percentage of that rating. That percentage is constant, no matter how much HP your car has, the drivetrain is only (e.g.) 80% efficient at translating that power directly to the pavement. So, your car has 200 HP, 80% is translated to the pavement, meaning its brake HP is 160 HP. If you increase your cars HP to 1000 (engine rated), it is transferring 800 HP to the pavement. Now, make that drivetrain just 5% more efficient… The difference at 200 (engine rated) HP is only 10 HP… But the Difference at 1000 is 50. You are getting 5 times more bang for your buck.

It is important to note that while the percentage is the same, in that example, it is merely an example. Horsepower in that example could be translated to “extra time off the charger” or not a percentage of battery life, but a percentage of screen on time increased. If it is proportionate, you are talking about maybe an extra 15 or 20 minutes of physical interaction with the device before it needs to be plugged in. Again, these are just examples, but the overall impact can be dramatic on a system that is already doing very well at providing the user a long duration of screen on time before it needs to be connected to a wall.

Another example would be gas mileage... this might be more relevant for what we are talking about. Imagine you have a car that is a big, mean v8, and literally gets 7 mpg. It has been way overdue for an oil change, and the oil is now causing the engine to run just slightly less efficient. Well, the car would likely run out of gas before you even noticed the loss in gas mileage, because it is already an inefficient mechanism when it comes to saving gas.

Take another car, that has a rated MPG of 60. Now imagine it is also overdue for an oil change. I would certainly say that the smallest bit of inefficiency in the engine, added weight to the vehicle, less aerodynamic it is… you will certainly see the effects of that more as its expected distance on a single tank of gas is 650 miles, as opposed to the other big v8, that can only go 80 total.

Imagine these two cars as older and newer technology in processors. The newer technology has greater potential for power saving simply because its baseline is already a fairly efficient platform. A small change will take it a greater distance. That car going 650 miles on one tank of gas… well, you’ll notice if that MPG drops by 3%... because you’ll be filling up at 600 miles.

In summary, if my phone is going to die after 2 hours of being off the charger anyways, because it has a small battery, or it’s display is chewing up 95% of the overall power draw, then yes, you are pretty much wasting your time playing with hardware settings otherwise. But that is not the case anymore. Mobile devices are the opposite – very efficient. Which means there is greater potential to minimize their power consumption by tuning, say, a CPU governor to not overreact to activity initiated by the user.

Again, very subjective statement made about 2%... It means nothing…. 2% could be 20 extra minutes of a phone call, 15 minutes of screen on time… etc. You see my point.