The Galaxy S5 feature that most impressed me in Barcelona was the Ultra Battery Saving Mode which reportedly gets you 24 hours of usage on just 10% battery life. I said it wouldn't be long before you saw the same thing on other devices and then the HTC One M8 came along with its Extreme Power Saving Mode which should get you 15 hours battery life on just 5% battery. So which one is better?
Both power saving modes take advantage of roughly the same features: limiting CPU usage, switching off haptic feedback and vibration, limiting background data, disabling data when the screen is turned off, limiting available apps and dropping screen brightness or color range.
The key difference between the two modes is actually hardware dependent: the Galaxy S5 has a Super AMOLED display while the One M8 has an LCD screen. AMOLED displays are pretty terrible in sunlight but they do have the advantage of generally being more battery friendly because pixels are only illuminated when they are colored. If your screen is mostly black then you're not using many pixels. LCD's, on the other hand, perform better outside but have to illuminate all pixels when the screen is on, even the black ones. Not surprisingly, the Galaxy S5 takes advantage of the power-saving effects of grayscale whereas the HTC One M8 power saving mode still uses color.
Access and implementation
Both power-saving modes are easily accessible from within the settings menu of each device. The Galaxy S5 only allows you to manually turn on the Ultra Power Saving Mode (it also features the regular power saving mode with restricted background data, limited CPU usage and grayscale options). Once switched on, the Galaxy S5 will take a little while to enable the mode and drop you to grayscale with limited app availability. Switching the mode off also takes a while.
The HTC One M8's Extreme Power Saving Mode, on the other hand, is lightning fast to enable and is equally simple to turn on and off. The big difference here is that besides being able to manually start and stop the mode, you can also program it to engage automatically when your battery life reaches a certain point, either 5%, 10% or 20% remaining. This is a big win in my opinion for the HTC. Like the S5, the One M8 also features a regular power saving mode as well. In terms of access and implementation I'd pick HTC as the winner for its speed and programmability.
Functionality and convenience
Functionally speaking, there's not a huge difference between the two modes, but what there is might make a big difference depending on what you're expecting. Both modes offer the usual dialing and text messaging functions, but the One M8 only has en email feature, whereas the S5 has full internet access (albeit in grayscale). Both modes have a couple of rather useless apps in their power saving mode like the calculator and calendar or clock, but the big difference here is that the S5 has two programmable extra spots for user-defined apps in Ultra Power Saving Mode. The list is short, but it's there.
The Galaxy S5 has the following apps as standard in Ultra Power Saving Mode: Phone, Messages, Internet and Clock, with the following options for the additional two spots: Calculator, ChatON, Google+, Memo and Voice Recorder. Perhaps not the most useful apps, but having access to Google+ and the full internet in a power saving mode is a huge bonus to me. The HTC One M8 has the following default apps available (with no alternative choices): Phone, Messages, Mail, Calendar and Calculator. If a power saving mode is important to you and something you imagine using regularly, you really need to weigh up what you need access to in a power saving mode. I think the S5 is the clear winner here.
Look and feel
Both modes are very similar and are even laid out very similarly. The main difference is that the Galaxy S5 drops to grayscale in Ultra Power Saving Mode and the HTC One M8 sticks with color. This makes the HTC's power saving mode much less of a noticeable change. Because the apps look generally the same you don't get the feeling that you've entered some restricted emergency mode like you do on the Galaxy S5. It's really up to personal preference, but I prefer the customization and additional functionality of the S5, but I like the look and feel of the HTC better. The S5 also seems to be a little more embedded within the wider system too – evident in the fact that you can still access a limited settings menu and Quick Notifications. This one's hard to pick a winner on.
The programmable Extreme Power Saving Mode on the HTC One M8 and the consistent feel of the mode compared to the regular usage of the device is a nice bonus for me. I also really like just how quickly the power saving mode turns on and off. However, the M8's mode is a little limited in my opinion with no options other than what HTC has provided. I really like the integration of the Galaxy S5's Ultra Power Saving Mode and the programmable app options, although the amount of time it takes to start and stop and the lack of an ''automatically engage'' feature is something I hope Samsung fix with a software update. Without enough time to fully test the battery times of both modes yet I can't peg a real winner, but at first glance I'm leaning towards the S5.
Do you think these modes are a gimmick or a truly useful feature? Can you see yourself using a power saving mode regularly?