Do not open the panel cover
This is the instruction no ranking page gives, and it matters more than anything else here.
Removing the cover exposes the busbars, which remain live with every breaker switched off, and the main lugs, which remain live even with the main breaker off because they sit on the utility side of it. There is nothing a homeowner can usefully see or do in there, and the fatal-accident statistics for panel work exist for exactly this reason.
Buzzing only when something is running
Why does the panel buzz only when the heat is on?
Because the noise is load-dependent, which narrows it to the breaker carrying that load or the termination behind it. A connection that is marginal makes no noise at rest and buzzes as soon as current flows through it.
Heating, air conditioning, electric dryers and well pumps are the usual triggers, because they draw hard and run for extended periods.
Write down which appliance is running when the sound starts. That single observation can turn a two-hour diagnostic into a twenty-minute one, because the electrician can apply that exact load and thermal-image the panel while it is present.
When to switch the main off
Isolating the whole house is disruptive, so it is worth being clear about when it is the right call.
- Switch the main off tonight if there is heat at the panel, any burning smell, visible scorching, or a sizzling sound.
- Isolate the affected circuit only if the noise is load-dependent and you can identify the breaker, and there is no heat or smell.
- Leave everything on and book a daytime call if the hum is faint, constant, unchanged for years, and nothing is warm.
Do all of it from a dry position with dry hands. If the panel is in a wet basement or you cannot reach it without standing in water, call your power company and ask them to cut supply at the meter instead. They do this routinely and do not charge for it in an emergency.
Can I sleep with the panel buzzing?
A buzzing electrical panel with a faint, unchanging hum, nothing warm and no smell: yes, and book a daytime appointment.
Crackling, sizzling, heat, scorching or any burning smell: no. Switch off the main and call tonight. A panel fault sits inside a metal enclosure full of conductors, and it has no early warning beyond the one you are already hearing.
Test your smoke alarms before bed either way. ESFI reports that 65 percent of home fire deaths occur in homes where no smoke alarm was working, which makes a tested alarm the most valuable thing in the building on a night like this. If a smell is present, read what a burning electrical smell means before deciding to stay.