Solar Panel Wattage Calculation Chart
Factor | Value | Unit |
---|---|---|
Panel Size | 1.6 | m² |
Solar Irradiance | 1000 | W/m² |
Panel Efficiency | 20% | – |
Temperature Coefficient | -0.4% | per °C |
Standard Test Conditions | 25 | °C |
Actual Temperature | 35 | °C |
Temperature Difference | 10 | °C |
Temperature Loss | 4% | – |
Theoretical Wattage | 320 | W |
Actual Wattage | 307.2 | W |
Solar Panel Wattage Calculation Formula
The formula for calculating solar panel wattage is:
W = A × r × η × [1 - α(T - 25)]
Where:
- W is the wattage output
- A is the panel area in m²
- r is the solar irradiance in W/m²
- η (eta) is the panel efficiency
- α (alpha) is the temperature coefficient
- T is the actual panel temperature in °C
Using the values from our table:
W = 1.6 × 1000 × 0.20 × [1 - 0.004(35 - 25)] = 320 × 0.96 = 307.2 W
How do you calculate solar panel wattage?
Here’s a detailed explanation of the process:
Determine panel size: Measure the panel’s dimensions to calculate its area in square meters.
Identify solar irradiance: Use the standard solar irradiance value of 1000 W/m² for comparison purposes.
Check panel efficiency: Find the manufacturer-specified efficiency rating, typically between 15-22% for modern panels.
Consider temperature effects:
- Note the panel’s temperature coefficient (usually -0.3% to -0.5% per °C above 25°C)
- Measure or estimate the actual panel temperature
- Calculate temperature-related efficiency loss
Apply the formula: Use the equation W = A × r × η × [1 – α(T – 25)]
Let’s use a 1.6 m² panel with 20% efficiency and a -0.4% per °C temperature coefficient, operating at 35°C:
- Panel area (A) = 1.6 m²
- Solar irradiance (r) = 1000 W/m²
- Panel efficiency (η) = 20% = 0.20
- Temperature coefficient (α) = -0.4% = -0.004
- Actual temperature (T) = 35°C
Theoretical wattage (at 25°C): W = 1.6 × 1000 × 0.20 = 320 W
Actual wattage (at 35°C): W = 1.6 × 1000 × 0.20 × [1 - 0.004(35 - 25)] = 320 × 0.96 = 307.2 W
This calculation shows that the panel’s actual output (307.2 W) is lower than its rated output (320 W) due to temperature-related efficiency losses.
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