Sony's Project Q announcement was puzzling to many (myself included). One could argue that it will last longer than other solutions by cutting out all the background bloat that otherwise hogs precious battery. However, that might not be the case according to Tom Henderson, the leaker who first talked about the handheld.
According to Tom, Project Q's battery life is pegged between 3-4 hours. That is what one can squeeze out of a Steam Deck and Nintendo Switch, and even the Switch OLED. Furthermore, these consoles run games natively, significantly increasing the load on the battery.
The only real-world scenario in which four hours of battery life is acceptable is when Project Q packs a top-of-the-line OLED panel. A proprietary Wi-Fi connectivity standard between Project Q and the PlayStation would also be excellent, even if it shaves off a few minutes of the battery life.
Tom adds that these figures are not final and could change with the commercial version of Project Q. After all, one has to account for the controller's battery usage, too, as it will likely draw power from the tablet. Will Sony let games use that controller with other devices? Can one connect their own DualSense for a similar experience? Only time will tell.