|If a powerline adapter was the issue it would be running VERY hot and you would have soon noticed. It would have to be faulty and would surely fail - a most unlikely reason for your issue.|
Watch your electricity meter. If it is a modern type it would be flashing very frequently on heavy load, or if the old type the disk would be spinning fast. You should be able to see what sets if going (if applicable). You can determine the load in W or kW from the difference between two readings - just a few sums.
Always pop back and let us know the outcome - thanks