We arrived at our clients home for concerns that the main thermostat was not working. Upon arrival, we immediately proceeded outside and verified that the outdoor condenser was receiving power and functioning. It is. Then proceeded inside and upon immediate visual inspection, we saw the lights flicker and shut off with the entire home. We went to inspect the breakers and ensure that everything was on at the main electrical panel for the home. We went into the attic and verified power was going to the indoor furnace, everything was on and working with no error codes displayed. The main thermostat was also on and displayed no error codes. While diagnosing the indoor equipment, the power went out again for the entire home. We placed the unit in test mode from the furnace and also the thermostat without any issues