Distance between floor and breaker panel?
I don't think there's a minimum height, but there's a maximum height for breaker handles.

240.24 Location in or on Premises.
(A) Accessibility. Overcurrent devices shall be readily accessible and shall be installed so that the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, is not more than 2.0 m (6 ft 7 in.) above the floor or working platform...

So for a main breaker panel, where the main breaker is at the top. The center of the main breaker handle, cannot be higher than 6' 7&quot;.
Check with the local building department, as they may have a minimum height.
Practically speaking, you'll want it at a comfortable height to work in. You're not going to want to sit, or kneel on the floor while working in the panel.