Testing the 5G capabilities of Apple's new iPhone 12 handsets isn't the easiest of jobs, given that 5G itself is only gradually rolling out across the world. Testers at our Munich office, for example, had problems accessing working 5G hotspots and tariffs. It's been easier for reviewers in the US - such as those at Tom's Guide - where the technology is more widespread.

Before reviewers could get started on their testing, however, details about the batteries in the new handsets were leaked. It turns out they are (perhaps surprisingly) a little smaller than in the iPhone 11 generation.

Apple is generally very good at extracting above-expected performance from suboptimal specs, of course, and the company has managed the impressive balancing act of delivering almost the same runtimes as the iPhone 11 with a smaller battery... but only if you limit yourself to 4G networks.

Now, we must first stress that a direct comparison with its predecessor using 5G is logically not possible because the iPhone 11 handsets don't support it. So we're not saying that the iPhone 12 is worse at dealing with the power demands of 5G than the iPhone 11. What we are saying is that 5G clearly drains the iPhone 12's battery faster than 4G.

Here are the facts: at 150 nits screen brightness and calling a website every 30 seconds via 4G, the iPhone 12 lasted 10 hours and 23 minutes. The iPhone 11 under the same conditions lasted 11 hours and 16 minutes. So the 12 is behind, but not by a huge distance.

The iPhone 12 Pro, meanwhile, delivered 11 hours and 24 minutes of battery life in the same test scenario, beating the iPhone 11 Pro (10 hours and 24 minutes) by exactly an hour.

But if the same test is repeated using 5G, the iPhone 12 runs for just 8 hours and 23 minutes, and the iPhone 12 Pro lasts 9 hours and 6 minutes. In both cases we're looking at a decrease of almost 20% in battery life.

And this isn't a fundamental problem with 5G, because competing Android phones all deliver better results under the same test conditions. The Samsung Galaxy S20 runs at 150 nits screen brightness and a new website every 30 seconds for almost 9 and a half hours, the Galaxy S20 Plus lasts 10 and a half hours, the OnePlus 8T 10 hours 49 minutes and the Google Pixel 5 almost 10 hours.

Apple appears to be aware of the power-drain issues with 5G use. In a support document the manufacturer describes how, when using the 5G Auto mode, the smartphone will switch to 4G if speeds are roughly equal to what would be expected from 5G. The 5G On mode, in contrast, always connects to 5G if available, but Apple warns that this can "reduce battery life".

In Low Power mode, which is offered when the battery charge drops below 20%, data traffic is automatically processed via 4G, unless the user is streaming videos.

(Update January 2021: There are specific reports suggesting that Some iPhones 12 models have battery problems. It's thought these could be caused by 5G)

This situation may change in the future: Apple's 2021 iPhones are rumoured to use Qualcomm's Snapdragon X60 which should mean less energy consumption and improved battery life. More here: 5G modem in 2021 iPhone will support better battery life.

Also, Apple is developing its own 5G modem, with a dedicated team working on the project following the acquisition of Intel's modem business in 2019. Read more about Apple's modem plans.

Read our guide to best iPhone 12 deals for the best bargains. Also read our iPhone 12 review and our iPhone 12 Pro review.

It's also been discovered that the iPhone 12 may be able to reverse charge AirPods.

This article originally appeared on Macwelt. Translation by David Price.