To know what size solar system is needed, several factors must be considered: the home's energy consumption, geographic location and sunlight availability, roof space, and panel efficiency. Here’s a general guide:
- Calculate your daily or yearly energy use in kilowatt-hours (kWh) from utility bills.
- Determine the average peak sunlight hours for your area.
- Use this formula to find the system capacity needed (in kilowatts):
System Capacity (kW)=Daily kWh UsagePeak Sunlight Hours\text{System Capacity (kW)}=\frac{\text{Daily kWh Usage}}{\text{Peak Sunlight Hours}}System Capacity (kW)=Peak Sunlight HoursDaily kWh Usage
- Divide the system capacity by the wattage of the solar panels you select (commonly 300-450W) to find the number of panels needed.
- Typical U.S. homes use about 886 kWh per month, often requiring between 15 and 22 panels for full coverage.
- Roof space must also accommodate the number of panels needed.
For example, a home using about 29 kWh per day with 5 peak sun hours would need a system around 5.8 kW. Choosing 300W panels would mean approximately 20 panels (5,800 W / 300 W per panel). Additional factors like roof orientation, shading, climate, and future energy needs (e.g., electric vehicles) will also influence the system size.
