To find the answers to these questions, I wore an Apple Watch Series 11 on my left wrist and the Apple Watch Series 12 on my right wrist, and analyzed the data from a seven-hour hike. The first half was spent in power-saving mode, the second half in normal workout mode. After the hike, both watches were left running in the background to measure my heart rate, display notifications, and show the time.
The following day, I exported and analyzed the telemetry data from both watches. WatchOS collects telemetry data at 15-minute intervals–in this test, that means that 60 data points were collected for the day (from 8 a.m. to 11 p.m.). A single day does not allow for any general conclusions about battery consumption, but it can indicate a trend.
Whether in power-saving mode or not, an Apple Watch runs continuously in the background during a workout. Both Apple Watches, Series 11 and 12, consistently recorded 900 seconds of background activity per 15 minutes; the power-saving mode setting had no effect on this. What does switch off, however, is the display. On average, it lights up much less frequently in power-saving mode, thereby conserving battery life.
As the energy capacity of each Apple Watch is known in watt-hours and the Battery system setting displays the percentage of maximum capacity, it is possible to calculate how much energy each Apple Watch can consume per hour and per quarter of an hour.
With the new Apple Watch Series 12, which has a 1.461 watt-hour battery and 100 percent of its maximum capacity, 14.61 milliwatt-hours of energy are consumed for every one percent of battery charge. With our Apple Watch Series 11, which has a 1.403 watt-hour battery and 98 percent of its maximum capacity, 13.74 milliwatt-hours are consumed per one percent of the battery charge.
The overall power consumption chart clearly shows that the two Apple Watches are on a par in power-saving mode. Background activities on both watches are running at full speed, while the display brightness is reduced to a minimum. It is only after power-saving mode is switched off that battery consumption increases on the Apple Watch Series 11. This is because, during that period, it was the actively paired watch and therefore had to deliver notifications and push alerts from the iPhone. The Series 12 was unpaired from the iPhone and did not have to perform these tasks.
