Now that Apple's next smartwatch has been officially announced, you may be wondering about the battery life of the Apple Watch Series 9. Historically, the Apple Watch has not been considered the best smartwatch in terms of battery life, but there have been several updates over the years that are worth noting.

For example, this year's flagship model features a 100% recycled cobalt battery, making the Apple Watch Series 9 Apple's first carbon neutral certified product family. While this does not affect battery performance, the watch's new S9 SiP promises a 25% improvement in power efficiency

, and the new S9 SiP is expected to be the first watch to be certified carbon-neutral.

While the improved performance is certainly welcome, it does not mean that the Apple Watch Series 9's battery life will be any different from recent models. In fact, this year's model increases the brightness of the Retina display from 1,000 to 2,000 nits, so the S9 chip is responsible for offsetting the display's higher power demands and ensuring that battery stamina is not compromised.

Most flagship Apple Watch models claim 18 hours of "all-day" battery life, while Apple Watch Series 7 and later models support fast charging, charging to 80% in just 45 minutes from battery dead.

In both respects (battery life and charging), the Apple Watch Series 9 is identical to the previous generation Apple Watch Series 8. It also features the Apple Watch's low-power mode that debuted last year. Low Power Mode is available on all Apple Watch models running watchOS 9 or the new watchOS 10 software coming September 18.

Since the Apple Watch Series 9 will come with watchOS 10, low-power mode will be available immediately. By disabling certain battery-draining features (such as Always On Display and continuous heart rate monitoring), low-power mode extends the smartwatch's battery life by up to 36 hours. In theory, if battery life is a priority, enabling low-power mode could double the standard battery estimate for the Apple Watch.

If battery life is a priority, you may want to consider the Apple Watch Ultra 2. Apple's revamped rugged sports watch features the same performance upgrades as the Apple Watch Series 9, including the U2 Ultra Wideband chip and a clever new double-tap feature.

Additionally, one of the biggest differences between the Apple Watch Ultra 2 and the Apple Watch Ultra is the display's brightness, which has been increased to 3,000 nits from 2,000 nits in the original. Even with the brighter display, the Apple Watch Ultra 2 has a battery life of 36 hours of normal use.

In low-power mode, the Apple Watch Ultra 2 has up to 72 hours of battery life, which is the highest battery life for an Apple Watch.