Having Flash installed can cut battery runtime considerably as much as 20 percent in our testing. With a handful of websites loaded in Safari, Flash-based ads kept the CPU running far more than seemed necessary, and the best time I recorded with Flash installed was just 4 hours. After deleting Flash, however, the MacBook Air ran for 6:02 with the exact same set of websites reloaded in Safari, and with static ads replacing the CPU-sucking Flash versions.
ArsTechnica: Just having Flash enabled cost 2 hours of battery life.
Time to kill Flash?