A 3kW solar system can generate 12 to 15 kWh of electricity per day and requires 10 300-watt solar panels, with a total system cost of $7,500 to $10,500 (not including tax credits). Losses come from inverter efficiency, wiring, temperature, and dirt. Increasing panel count or choosing higher wattage. Our solar panel calculator helps homeowners and installers plan photovoltaic systems. Estimate how many panels you need based on energy consumption, calculate expected output based on location and panel specifications, and see potential cost savings over time.