The useful answer is not a universal number—it depends on how much energy you use, how much sunlight reaches your location, panel wattage and system losses.
The quick method
Start with your average daily electricity use. Divide the energy you want solar to supply by your average peak sun hours and a realistic system-efficiency factor. That gives an estimated array size in kilowatts.
Then divide the array wattage by the wattage of one panel and round up.
Why peak sun hours matter
Five peak sun hours does not mean the sun shines for only five hours. It converts changing sunlight throughout the day into the equivalent number of hours at full rated irradiance.
Do not stop at panel count
A complete system also needs an inverter sized for simultaneous loads, optional battery storage based on backup goals, mounting, protection and a final compatibility check.
Calculate panel count → Build a complete system →
Educational estimate only. Final electrical and structural design should be completed by qualified professionals.