The iPhone 15 needs to fix this one iPhone 14 weakness

iPhone 14
(Image credit: Tom's Guide)

The iPhone 15 promises lots of anticipated changes, and everyone has their favorite rumored feature. From the arrival of the Dynamic Island on the less expensive models to a purported switch from Lightning to USB-C across the iPhone lineup, there are plenty of potential iPhone 15 features to get excited about.

But there's one change that Apple will need to make to ensure that the iPhone 15 tops the list of best iPhones as a worthy successor to the iPhone 14 lineup it will replace this fall. And that's making sure the battery life on the new phones is up to snuff.

That's less of a concern for the 6.7-inch iPhones. Both the iPhone 14 Plus and iPhone 14 Pro Max turned in outstanding times on our battery test, landing on our best phone battery life list. The 6.1-inch models, in contrast, had a harder time keeping up, particularly the iPhone 14, which finished behind the average smartphone in our battery testing.

Outside of camera performance, few things are as critical to a phone's success as how long it can last on a charge. Our phones are our constant companions — the device we rely on the most. The last thing we want to see when we're checking an important message, getting directions or making a phone call is a low battery indicator and no charging options in sight.

That's why if Apple does nothing else with the iPhone 15 lineup, boosting the battery life of the 6.1-inch models is critical. Here's a look at the recent history of the iPhone's ability to last a long time on a charge and what Apple's prospects for bolstering the iPhone 15's longevity are.

iPhone battery results (so far)

Swipe to scroll horizontally
Longest-lasting iPhones
PhoneYear releasedBattery sizeBattery life (Hrs: Mins)
iPhone 14 Pro20224,323 mAh13:39
iPhone 13 Pro20213.095 mAh12:18
iPhone 13 Pro Max20214,352 mAh12:16
iPhone 14 Plus20224,325 mAh11:57
iPhone 12 Pro Max20203,687 mAh10:53
iPHone 1320213,227 mAh10:33
iPhone 14 Pro20223,200 mAh10:13
iPhone 1420223,279 mAh9:28
iPhone 12 Pro20202,815 mAh9:06
iPhone 13 mini20212,406 mAh8:54
iPhone 1220202,815 mAh8:25
iPhone 12 mini20202,227 mAh7:28
Row 13 - Cell 0 Row 13 - Cell 1 Row 13 - Cell 2 Row 13 - Cell 3

For the most part, iPhones have enjoyed a fairly positive reputation when it comes to battery life, usually ranking among the longer-lasting phones in a given year. But there was one recent exception to that — 2020's iPhone 12 release. 

The iPhone 12 was the first Apple phone to offer 5G connectivity, and 5G proved to be a very power-hungry feature. Both the iPhone 12 and iPhone 12 Pro took big steps back from their predecessors on our battery test, in which we have fully charged phones surf the web continuously over cellular until they run out of power. The iPhone 12 mini, a new addition to that year's Apple lineup, posted the worst time of any of the new Apple phones. Only the iPhone 12 Pro Max, which benefitted from a larger battery, beat the average result for a smartphone on our test.

We clearly weren't the only ones to notice an issue with battery life for the iPhone 12 lineup because when it came time to release the iPhone 13, Apple — which never discloses battery sizes — made a point of emphasizing that all four models were getting bigger power packs than the ones in the iPhone 12. That certainly paid off, as all four iPhone 13 model turned in improved battery performance.

That brings us to the current iPhones. As noted above, the iPhone 14 Plus and iPhone 14 Pro Max are powerhouses when it comes to battery life, with the Pro Max in particular turning in a time of 13 hours and 39 minutes. That's the second longest result we've seen in the last year-and-a-half of testing phones. 

It's the smaller iPhones where we have a concern. On the surface, the iPhone 14 Pro time of 10 hours and 13 minutes is nothing to sniff at — it's ahead of the average time for smartphones by about 20 minutes. But it's also more than 1.5 hours shy of the time the iPhone 13 Pro turned in, and we're puzzled as to why.

The iPhone 14 is even more concerning, finishing a half-hour behind the average smartphone. Given the cozy confines of these two 6.1-inch phones, we struggle to see how Apple can increase the battery size beyond the 3,279 mAh and 3,200 mAh cells that power the iPhone 14 and iPhone 14 Pro, respectively.

What's ahead for iPhone 15 battery life

iPhone 15 Pro renders by Technizo

(Image credit: Technizo)

For the iPhone 15 Pro, Apple may have a trick up its sleeve in the form of the A17 Bionic chip likely to power this year's Pro models. The A17 is slated to be built on a 3-nanometer process compared to the A16 Bionic, which is built on a 4nm or 5nm process depending on who you ask. (Apple says the former, while chipmaker TSMC describes it as more of an enhanced 5nm process.)

Regardless, the switch to a 3nm chip is a significant one, as you can pack in transistors more densely. That generally leads to gains in performance and, for our purposes, power efficiency. So you'd expect to see the iPhone 15 Pro do a better job at managing power than the iPhone 14 Pro did, just by the virtue of upgrading processors.

We've also heard rumors of a new micro-processor for the iPhone 15 Pro that replaces the existing “Super Low Energy Mode” in the iPhone’s chipset. That mode is what lets you use Apple Pay or the Bluetooth Find My tracking when the iPhone has died or is switched off. The user claims that Apple is testing the micro-processor's ability to do all this and detect various capacitive button presses when the phone is switched off. 

So where does that leave the iPhone 15? It's due for a chipset upgrade, too, likely switching from the iPhone 14's A15 Bionic to the A16 Bionic found in the current Pro models. That could lead to some battery life improvement — remember, the iPhone 14 Pro outlasts the standard iPhone 14 on our test — though without other changes, the iPhone 15 would likely have the worst battery life of the models Apple introduces this fall.

Maybe that's the trade-off you accept for opting for the entry-level iPhone. Apple certainly seems focused on packing in premium features to its Pro models as of late, and that's likely to continue this fall, as our iPhone 15 vs. iPhone 15 Pro rumor comparison makes clear. Still, Apple will have some motivation to make the least expensive iPhone 15 feel like a worthwhile upgrade and bolstering the battery life would be one way to tick that box.

iPhone 15 battery life outlook

While there are plenty of rumors about potential iPhone 15 features, we haven't heard much about whether Apple is planning to — or even able to — increase the size of the cells that will power its upcoming phones. Those details, along with other iPhone 15 specs, should leak out the closer we get to the phones' likely launch date in the fall.

Whatever ends up happening, there's no denying that battery life is a key feature for any phone. And it's one aspect of the iPhone 15 that will merit close scrutiny come the fall.

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Philip Michaels

Philip Michaels is a Managing Editor at Tom's Guide. He's been covering personal technology since 1999 and was in the building when Steve Jobs showed off the iPhone for the first time. He's been evaluating smartphones since that first iPhone debuted in 2007, and he's been following phone carriers and smartphone plans since 2015. He has strong opinions about Apple, the Oakland Athletics, old movies and proper butchery techniques. Follow him at @PhilipMichaels.