The problem this solves is a quiet one. You plan to add a load to the house, and the panel decides whether the plan works. Most homes were wired around the loads that existed when they were built. A new appliance, or another large draw on the same circuits, can ask more of the panel than the house was built to give.
Start by reading the panel from the outside. Do not open it to look. The main rating is usually printed on the door label. Note whether there are open spaces for new breakers. A panel with no open positions is telling you something about its room.
Next, write down the large loads already on the house. Include the range, the clothes dryer, the central air or heat pump, the water heater, and any workshop circuit. Note which ones run at the same time on a normal day. The overlap is what the panel actually feels.
Watch for the signs that you already have a capacity problem. A breaker that trips when large loads start together is one. A breaker that feels warm under normal use is another. A panel with a mix of old and new breakers, or a sub-panel added years ago, deserves a closer look. None of these means the panel is failing. They mean the layout needs a professional look before you add more.
Ask a licensed electrician to run the load calculation. The calculation adds the loads, applies the rules for each type, and shows whether the panel has room for the new appliance. Ask whether the service needs upgrading before the addition, and ask for the answer in writing. Compare that answer with the panel label and the list you wrote.
Use the age of the panel as a planning input. The electrical panel page on this site lists its typical service life and the points where a planning date makes sense. An old, crowded panel is a good candidate for a combined plan, where the new appliance and any service work are scoped together.
Keep the list. Record the appliances, their timing, the panel label, the open spaces, and the electrician's written answer on the same page. When the next appliance comes up, that page will show whether the panel has room before anyone starts cutting into the wall.