It seems as that every time a battery backup sump pump was needed around here it wouldn't have worked anyway. I have two sump pumps, both of whichrun ocasionally on a normal basis. When we havw a long rainy spell one pump couldn't keep up so I installed another. Two are still busy. From the directions on the box it appears that the "Ace-in-a-hole" was just prolonging the fact that we were floodind. Sometimes we don't have electricity for several hours, days even. I purchased a "Coleman" 6000 watt generator and can even run essential appliences, lights, refrig. etc while keeping the basement dry. Two catches: It's more of an expensive investment. You must be present to start the system I have.