The answer to 'panel upgrade making buzzing noise' is that a buzzing sound coming from an electrical panel after an upgrade is often caused by loose connections or an overloaded circuit. This can be a serious issue that requires prompt attention to prevent potential fire hazards or other electrical problems.
Some common causes of a buzzing electrical panel include loose wiring connections, an overloaded circuit, faulty circuit breakers, or a problem with the panel itself. The buzzing sound is typically an indication that there is an issue with the electrical system that needs to be addressed by a professional electrician.