From an electrical standpoint it's safe as long as your inverter cuts off when grid power goes out. Grid tie inverters are designed to do that. Some meters wil

From an electrical standpoint it's safe as long as your inverter cuts off when grid power goes out. Grid tie inverters are designed to do that. Some meters will be unhappy running backwards. They may not register the right numbers but they won't blow up. From a regulatory standpoint your utility won't be happy with you feeding power to the grid if you haven't notified them ahead of time. How unsafe that is depends on your local laws. The dangers here are fines and service cutoffs, not fires and electrocution.