Solar Panel Sizing Calculator
Calculate solar panel wattage, battery capacity, and charge controller current for off-grid photovoltaic systems based on load and sun hours
Formula
P_panel = (P_load × 24) / PSH × 1.25, C_batt = P_load × 24 × N_days / V_sys / 0.5
How It Works
Solar panel sizing involves calculating the electrical power generation capacity needed to meet specific energy requirements. This process depends on understanding photovoltaic conversion efficiency, which transforms solar radiation into electrical energy through the photovoltaic effect. The fundamental calculation requires analyzing total energy consumption, solar irradiance levels, panel efficiency, and system losses to determine the appropriate panel size and configuration.
Worked Example
Calculate solar panel requirements for a home consuming 1000 kWh monthly. Given solar irradiance of 5 peak sun hours daily and using 300W panels with 18% efficiency: 1. Daily energy requirement = 1000 kWh / 30 days = 33.33 kWh/day. 2. Required panel output = 33.33 kWh / 5 peak sun hours = 6.67 kW. 3. Number of panels = 6.67 kW / 0.3 kW per panel = 22.23 panels (rounded to 23 panels).
Practical Tips
- ✓Always include a 20-25% safety margin in panel sizing calculations
- ✓Consider seasonal solar irradiance variations in your region
- ✓Account for panel degradation of approximately 0.5-0.8% annually
- ✓Choose panels with higher efficiency for limited installation spaces
Common Mistakes
- ✗Neglecting system losses in power conversion
- ✗Failing to consider local weather and shading conditions
- ✗Using average solar irradiance instead of conservative estimates
- ✗Overlooking panel orientation and tilt angle impacts
Frequently Asked Questions
How do I determine peak sun hours?
Peak sun hours are location-specific and can be found through solar radiation maps or local meteorological data, representing hours of maximum solar intensity equivalent to 1 kW/m².
What efficiency should I expect from solar panels?
Modern commercial solar panels typically range between 15-22% efficiency, with high-end monocrystalline panels reaching up to 22-25%.
How often should solar panels be replaced?
Most solar panels have a warranted lifespan of 25-30 years, with performance gradually degrading to about 80% of initial capacity over this period.
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