The actual chance of your generator backfeeding the grid is nigh nill. The issue is that all your neighbors are still connected. The moment your generator touch

The actual chance of your generator backfeeding the grid is nigh nill. The issue is that all your neighbors are still connected. The moment your generator touches the grid it acts as pretty much a dead short. Not saying it can't happen. The main one where it could is if the break is between your house and everybody else. But in the vast majority of situations you will instantly pop the dinky 15a breaker