iOS 17 vs iOS 18: Stability, Battery Life and Performance After a Year

With the release of iOS 18, Apple continues its cycle of annual operating system updates. For users of the iPhone 13, 14 and 15 lineups, a common question emerges — how does the latest system compare to iOS 17 in everyday use after a year? This article explores real-world experiences of iOS 18 and benchmarks it against its predecessor in terms of stability, battery life, and overall performance.

System Stability in Everyday Use

When it comes to system stability, iOS 17 proved to be one of Apple’s more reliable releases in recent years. After several months of patches and updates, most bugs were ironed out, and devices such as iPhone 14 and 15 ran smoothly in both native and third-party apps.

iOS 18 launched with a solid foundation, particularly for newer iPhones. In practical usage, app crashes became rarer, multitasking improved slightly, and system animations ran more fluidly. However, some minor bugs were reported in the first month after the public release, such as temporary UI glitches on older devices like iPhone 12.

Apple seems to have shifted its focus toward long-term usability. The new update introduces fewer radical changes and instead offers a more polished and refined user experience. Stability improvements are most noticeable on the iPhone 14 Pro and 15 Pro, where ProMotion and background processing now operate more consistently.

Software Optimisation for Different Models

iOS 18 has clearly been optimised for Apple’s most recent hardware. Devices from the iPhone 13 and 14 series benefit from smoother multitasking, fewer frame drops, and enhanced app responsiveness compared to iOS 17. On the iPhone 15 Pro models, the adaptive refresh rate feels more stable under iOS 18.

However, older models such as the iPhone 11 and XR see less benefit. While they remain compatible, there are occasional performance stutters and lag in animations. This is a clear sign that Apple continues to optimise new updates primarily for its recent devices.

In general, users who upgraded to iOS 18 on iPhone 13 and newer models report more stability across core apps like Safari, Mail, and Messages, especially under heavy usage or background load.

Battery Performance After Long-Term Use

Battery life remains one of the most critical aspects for daily users. With iOS 17, battery performance on release was decent but required several incremental updates to reach a stable point. By mid-2024, iOS 17 had become efficient for devices like the iPhone 14 and 15.

Under iOS 18, battery performance varies depending on the model. On iPhone 15 Pro, the battery management appears smarter, with improved idle drain and app usage monitoring. Users reported an increase of around 5–8% in screen-on time compared to iOS 17.

However, on devices older than iPhone 13, iOS 18 doesn’t deliver any significant improvement. In fact, in some cases, battery drain during standby has become slightly worse due to background AI-related features, even when not used actively.

Adaptive Power Management in iOS 18

iOS 18 introduces more advanced power-saving algorithms that dynamically adjust system resources based on usage patterns. This is most beneficial on newer devices equipped with A16 and A17 chips, where background processes are offloaded to low-power cores more efficiently.

Night charging behaviour has also improved. The system better predicts user habits, charging more intelligently overnight to reduce battery wear. This change extends battery health, particularly helpful for users who charge their phones daily at the same time.

Overall, while not revolutionary, the energy optimisation in iOS 18 brings marginal but consistent gains for newer models. For older iPhones, battery life remains comparable to iOS 17 without significant improvements.

Performance and Speed Comparison

Performance is often the most noticeable change with major updates. iOS 17, by the end of its lifecycle, delivered solid speed on most iPhones released since 2020. Launch times were stable, and system animations remained fluid even under load.

iOS 18 builds on this with improved GPU management and faster app launching, especially for native apps. On iPhone 15 Pro, benchmarks show a 10–12% improvement in app startup time and smoother in-app transitions due to better utilisation of hardware acceleration.

However, for the iPhone 12 series and older, performance is largely unchanged or marginally lower due to the heavier system footprint. iOS 18 introduces new AI features that, while optional, run in the background and require additional resources.

AI and On-Device Intelligence Impact

One of the key features of iOS 18 is on-device AI integration for tasks like predictive typing, Siri suggestions, and content personalisation. These features are hardware-dependent and run best on iPhones with at least an A16 chip.

Performance on the latest models benefits from these AI enhancements, with apps like Notes and Mail now offering real-time suggestions without noticeable delay. However, older models may experience slower response times or reduced functionality, as some features are disabled by default to preserve performance.

While Apple markets these AI tools as background enhancements, their impact on overall speed is real, especially when multitasking or switching between apps. Users should consider their usage patterns when deciding whether to enable all new features.