https://wccftech.com/new-battery-test-shows-how-promotion-display-on-iphone-13-pro-improves-battery-life/

Apple launched the iPhone 13 series last year and this time around the company has increased the gap between the standard and the 'Pro' models. While battery life on the iPhone 13 has been greatly improved, the iPhone 13 Pro models feature the new 120Hz ProMotion display. The variable refresh rate offers an enhanced experience as well as contributes to saving battery life. In a new battery life comparison video of the iPhone 13 Pro against the iPhone 13, a user shows the improvement the ProMotion display brings to the table.

The battery test comparison is conducted by PhoneBuff and shared on YouTube. On paper, the standard iPhone 13 features a bigger battery than the iPhone 13 Pro - 3227mAh and 3100mAh, respectively. In addition, both iPhone models feature a 6.1-inch display but the iPhone 13 Pro houses a 120Hz ProMotion display with variable refresh rates. What this means is that the iPhone 13 Pro can go as low as 10Hz when needed.