Solar kWh Output Calculator
Estimate the daily, monthly, and annual kilowatt-hour (kWh) production of your solar panel system.
Enter the peak wattage of a single solar panel (e.g., 400 Wp).
Total number of panels in your system.
Average hours per day your panels receive direct, effective sunlight (e.g., 4.5 for many US regions).
Accounts for system losses (temperature, shading, wiring, inverter efficiency). Typically 70-85% (e.g., 78 for 78%).
Understanding Your Solar Energy Production
A solar kWh output calculator is an essential tool for anyone considering or already owning a solar panel system. It helps you estimate how much electricity, measured in kilowatt-hours (kWh), your system can generate over a day, month, or year. This estimation is crucial for understanding potential savings, system sizing, and return on investment.
How the Calculator Works
Our calculator uses a straightforward formula to estimate your solar energy production, taking into account several key factors:
- Individual Panel Wattage (Wp): This is the maximum power output a single solar panel can produce under ideal test conditions. Modern residential panels typically range from 300 Wp to 450 Wp. Higher wattage panels mean more power per panel.
- Number of Solar Panels: The total quantity of panels in your array directly scales your system's potential output. More panels generally mean more electricity generation.
- Average Daily Peak Sun Hours: This is not simply the number of hours the sun is visible, but rather the equivalent number of hours per day when solar irradiance averages 1,000 watts per square meter. This value varies significantly by geographic location and time of year. For example, a sunny region might have 5-6 peak sun hours, while a cloudier region might have 3-4.
- System Derate Factor (%): No solar system operates at 100% efficiency in real-world conditions. The derate factor accounts for various losses, including:
- Temperature losses (panels are less efficient when hot)
- Shading from trees, chimneys, or other obstructions
- Wiring losses
- Inverter efficiency (converting DC to AC power)
- Dust and dirt accumulation on panels
The Calculation Formula
The core calculation is as follows:
Total System kW = (Individual Panel Wattage * Number of Panels) / 1000
Daily kWh Output = Total System kW * Average Daily Peak Sun Hours * (System Derate Factor / 100)
From the daily output, we then extrapolate to monthly and annual figures.
Example Calculation
Let's say you have:
- Individual Panel Wattage: 400 Wp
- Number of Solar Panels: 15
- Average Daily Peak Sun Hours: 5 hours
- System Derate Factor: 78%
- Total System kW: (400 Wp * 15 panels) / 1000 = 6000 W / 1000 = 6 kW
- Daily kWh Output: 6 kW * 5 hours * (78 / 100) = 6 * 5 * 0.78 = 23.4 kWh
- Monthly kWh Output: 23.4 kWh/day * (365 days / 12 months) ≈ 711.9 kWh
- Annual kWh Output: 23.4 kWh/day * 365 days = 8541 kWh
This means your system could produce approximately 23.4 kWh per day, 711.9 kWh per month, and 8541 kWh per year under these conditions.
Why is this important?
Knowing your estimated kWh output helps you:
- Size Your System: Determine if the proposed system can meet your household's electricity needs.
- Estimate Savings: Calculate how much you might save on your electricity bills by offsetting grid consumption.
- Evaluate Payback Period: Understand how long it will take for your solar investment to pay for itself.
- Compare Quotes: Assess the performance claims of different solar installers.
While this calculator provides a good estimate, actual production can vary due to weather fluctuations, seasonal changes, and unforeseen system issues. For precise figures, consult with a professional solar installer who can perform a detailed site assessment.