Single phase loss causes partial power outage and non-functioning breakers on affected branch. Inspect the incoming utility feed and meter for faults. Most residential properties in North America use a split-phase system, consisting of two separate 120-volt lines, or “hot. The good news is that all inverters listed for tying to the grid have that feature built-in. If I put any appliance (be it a small light bulb) the power disappears on the same phase until main switch is turned -> off -> on. At the main breaker in my box I can test each phase 1 Has 120 V the other I lost one phase of electricity in my house. Clearly, at this point, every other. Imagine your production line suddenly halts, or your home appliances start acting up.