With any normal load such as a lamp, heater or motor, the voltage at the load will allways be less than at the panel, the difference may be significant or it may be trivial, but it will allways be less at the load.
An apparently higher reading at the load would suggest a defective instrument, operator error or a change in line voltage between taking the two readings.
In this case however what is connected is not truly a load at all, but is a SOURCE of energy.
The voltage at the source (grid tied inverter) will allways be higher than at the panel.
Again the difference may be significant, or may be trivial, but it MUST be higher at the inverter (presuming that it is running)