A good surge protector, like this APC unit, will tell you how much energy it can safely absorb—in this case, 2,880 joules, which is quite a lot. If you experience a lot of surges, eventually your surge protector will run out of protection. In really unstable areas, you might have to replace a surge protector every five years or so. But what’s great about the best surge protectors is that they guarantee your electronics. If a surge makes it through the APC and zaps your computer? You’re covered, up to $250,000. Think of it as a form of insurance.