About 97% of solar panels quoted on the EnergySage Marketplace in 2025 are 400 to 460 watts—expect to see panel outputs in this range in your quotes. Your panels' actual output will depend on your roof's shading, orientation, and hours of sun exposure. But wattage alone doesn't tell the whole story. In fact, efficiency matters more than wattage when comparing solar panels—a higher wattage can simply. . While it varies from home to home, US households typically need between 10 and 20 solar panels to fully offset how much electricity they use throughout the year. The goal of most solar projects is to offset your electric bill 100%, so your solar system is sized to fit your average electricity use. . Solar panels degrade slowly, losing about 0. 5 kWh of energy per day, depending on local. . While calculating these numbers yourself can give you an idea of what kind of solar array you'll need, know that one of the best solar companies (like Tesla) will do all of these calculations for you if you proceed with installing solar panels. A four-to-five-person household likely needs a four to five KW system. The roof size and condition, hours of peak sunlight. . Determine Solar Panel Output: The output of solar panels varies based on their wattage and the amount of sunlight they receive.