An electrical box assembly for a solar energy module that includes a lid having outer flanges and a box having slide chutes. The electrical box is assembled by gliding the outer flanges of the lid into the chutes of the box. Using a method, the object will not easily come apart. After the lid has been assembled with the box and covers the box, the through holes of the lid will corresponded to the fastener receiving apertures of the box allowing the fasteners to fix together. A set of shelves includes a first shelf and a second shelf, which can be secured into the first slot and the second slot of the box individually, allowing for electrical parts or devices to be installed on the shelves. In addition, the box, the lid and the shelves are all made of aluminum alloys which can enhance the efficiency of the heat radiation, accomplishing the goal of high heat conductivity and low rate of malfunction.