Place a wall-mounted cabinet over the electrical box. To make your cabinet fit around the panel and allow you access to the panel doors, you may need to remove some or all of the shelves inside the cabinet. Some wall-mounted cabinets have a wooden back, but others do not. Use a pry bar to remove the wooden back, or use a power saw to cut through the back of the cabinet. Sand the new edges, and mount the cabinet as per the manufacturer's instructions.
Bookcase With Doors
Position an inexpensive bookcase over the wall where your electrical panel is. Purchase a bookcase that comes with a flimsy cardboard backing that you can leave off when you assemble it. Position the shelves so they are not blocking access to the panel box. You may use the shelves to hold some items, but do not place clutter in front of the box.
An armoire is a large cabinet with doors on the front. You'll need to remove the back of the armoire, or assemble it without the back attached. The armoire should be shallow enough that you can reach inside and access the interior parts of the electrical box easily. Although you should not use the area in front of the panel box for storage, other parts of the armoire may be used for these purposes.
Some electrical panels are recessed into the wall, while others are mounted on the wall. Obviously, an electrical panel mounted on the wall will require a deeper cabinet than a recessed panel. Don't use a cabinet so deep that you find it difficult to reach the circuit breakers or fuses in the box. You will probably also see a thick electrical wire leading from the top of the panel box into the rest of the house. Before you put a cabinet in front of the panel, you'll need to measure the width and depth of the cable and cut a niche in the back of the cabinet large enough to fit around the cable. Do not use the small wall-mounted cabinet for storage, but larger units like the armoire may be used for storage. Do not put anything containing liquid in the cabinet.
Check local building and safety codes before placing anything in front of your electrical panel. Some states have codes about the clearance space required around electrical panels. Even if your state codes allow you to place a cabinet in front of your panel, you should have quick access to your panel box in the event that you need to turn off your power in a hurry. Aside from the cabinet doors, which should be easy to open, don't place anything in front of the panel that will prevent the door from swinging open 90 degrees. Put a stick-on light inside the cabinet that you can turn on when doing work in the electrical panel.