Arrived on site to troubleshoot flickering lights in the office. I checked voltage at main panel and outside equipment. Voltage coming in is steady and correct. I checked connections at the main panel and outside equipment. Everything is tight with minimal corrosion. They do have a power back up they were using. Once they unplugged that, the flickering lights stopped. I recommend investing in a new battery backup. I also recommend getting the power company out to test their wires. I did recommend install surge protection for all electrical panels in the office. Everything is working upon departure.