The iPhone 6's stamina promised to be a lot better than that of the iPhone 5S, as it comes with a 25% longer lasting battery and, according to Apple's literature, the A8 processor at the heart of things is a much more efficient engine, drawing 50% less power than the A7 iteration in the last iPhone.

The good news is battery life in the iPhone 6 is definitely an improvement on what came before, offering a much more stable experience even if you're not doing much with the phone, which was one of my major gripes with the iPhone 5S.

There's a notion that what Apple offered with that device was 'good enough', according to the owners I spoke to, but all wished that something could be done to make it better.

iPhone 6 review

When informed that 2014's crop of Android phones, such as the Samsung Galaxy S5 or HTC One M8, were capable of lasting well over a day even on harder usage, most realised that Apple needed to do something to improve the time they could keep away from a charger.

Well, at least that's happened with the iPhone 6. When it first launched, in average use – by which I mean email being fetched at intervals, the screen at medium brightness, recording a few minutes' worth of video, snapping seven photos, and an hour or two spent listening to offline tracks on Spotify – I managed to go 13 hours with the battery only dropping to 33%.

From then I played Real Racing 3 for 15 minutes and lost 10% of the battery life, which showed that it's very easy to slip through power when playing graphically intensive games.

Returning to an iPhone 6 handset that's been in use for more than a year, I was pleased to find that its stamina remained pretty decent – after 12 hours of light usage it had dropped to just 46%. Of course, iPhones have always been extremely good at not being used much – they truly sip the power when in standby, with the screen powered down.

As was the case earlier in its life, playing 3D games really hit this 'mature' iPhone 6's battery where it hurts. Playing 10 minutes of Freeblade – the graphically-rich shooter Apple used to show off the iPhone 6S at launch – sapped around 15% of the battery's charge.

Another persistent issue: try and do anything like downloading music (which needs the screen to stay on, as apps like Spotify can't manage downloading in the background) and the battery will just fall away, meaning you'll be back to playing the charger hunt game.

It should be noted that this is generally a problem with most smartphones; however, some are more adept at it than others (the fact Android phones can download in the background, for instance, is a great boon).

It's also worth noting that Apple added a Low Power Mode with iOS 9. Flipping this on manually (you'll also be granted the option when power hits 20%) reduces things like mail fetch and background app refresh frequency, as well as automatic downloads and iOS's flashier visual effects.

In truth, this is a feature Apple should really have added some time ago. Still, we're glad it's finally here for those times when you're caught away from a wall socket.

Our techradar battery test did show something slightly worrying, and likely down to the increased pixel count: where the iPhone 5S lost 16% from a looped 90-minute Full HD video, the iPhone 6 lost 26%, with the iPhone 6 Plus dropping a similar 27%. Apple's extra pixel management clearly isn't as good as it could be, so anything with the screen on is going to be an issue.

After a few months' use I found that the battery wasn't as robust as in other phones, with the iPhone 6 starting to show a worrying tendency to juice down to about 20% at home time. It could have been due to heavier apps being plugged in – running apps seem to want to spend time in the background eating battery – but it's not something I've seen on comparable handsets.

More recently, I put the iPhone 6 through its paces on the aforementioned techradar battery test once again, and found that the average remaining figure had dropped to 67% – quite a deterioration from launch.

In summary though, the battery life of the iPhone 6 is still something I'd call more than adequate, which isn't a compliment I'd pay previous versions of this phone.

That said, given the lower-res screen and improvement in battery size, I was hoping for something a little more efficient, especially as the iPhone 6 can't quite compete with other phones on the market at the moment.

It's not miles behind, but there's still some work to be done by Apple for the iPhone 7 (the iPhone 6S offers pretty much the same performance from a slightly smaller battery). And especially given that the iPhone 6 Plus and iPhone 6S Plus are so much better at lasting with the screen off (thanks to the much larger power pack), this is going to lead to a tricky decision for prospective buyers.