You might want to check whether your main power board has a smart meter that monitors power usage and transmits power usage info back to supplier at regular intervals.
Alternatively the source could be from neighbours, there are so many sources for wifi these days - routers, phones, many household appliances now have wifi active.
Alternatively the source could be from neighbours, there are so many sources for wifi these days - routers, phones, many household appliances now have wifi active.