The answer to 'panel upgrade gets hot' is that a hot electrical panel is often a sign of a serious issue that requires immediate attention from a licensed electrician. This can be caused by faulty wiring, an overloaded circuit, or a problem with the panel itself. Symptoms may include the panel feeling hot to the touch, flickering lights, or circuit breakers tripping frequently.
Trying to troubleshoot or repair a hot electrical panel on your own can be extremely dangerous and should not be attempted. Homeowners should immediately shut off power to the panel and call a professional electrician to diagnose and fix the problem. Attempting DIY repairs on a hot panel could lead to electric shock, fire, or other life-threatening hazards.