Solar Panel Sizing Calculator

Sun hours vary by location and season. Most areas in the US receive 4-6 peak sun hours daily. Winter months typically have fewer sun hours, so it's important to size your system based on the darkest months for year-round reliability.

Modern residential solar panels typically range from 300-500 watts. Higher wattage panels mean fewer total panels needed, but they may cost more per panel. 400W panels offer a good balance of efficiency and cost.

Check your electricity bill for your monthly kWh consumption. Look for a 12-month average to account for seasonal variations. Most homes use between 600-1200 kWh per month.

System losses account for energy lost through inverters, wiring, shading, and weather conditions. Typical losses range from 12-18%. These losses reduce your actual energy production below the theoretical maximum.

Most homeowners aim for 100% offset, but you can choose based on your budget and goals. Some prefer 75-90% offset to minimize costs, while others choose 110-125% to account for future increases in usage or to sell excess power back to the grid.

Each panel typically requires about 15-20 square feet including spacing. A typical residential system needs 300-600 square feet of roof space, depending on system size and panel efficiency.

Yes, this calculator works for both grid-tied and off-grid systems. For off-grid applications, consider sizing your system 25-50% larger to account for battery storage inefficiencies and cloudy weather periods.

Many homeowners increase their energy usage after going solar (electric vehicles, heat pumps, etc.). Consider your future energy needs when sizing your system, or plan for a system that can be expanded later.