A power surge is a significant increase in voltage that can last three nanoseconds or more. If the surge is high enough, it can cause some heavy damage to your home appliances. Trust me, I know. I once had a power surge and lost thousands of dollars in appliances - including a brand new TV. That hurt. That's why we install one in every single home we work on, even if we are not touching the electrical work in that house. I always recommend you PROTECT IT RIGHT and a whole home surge protector is a MUST!