Solar Power Calculator
Estimate how much electricity your solar system can generate daily, monthly, and yearly based on your location's sunlight and panel specifications.
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How to Use This Solar Power Calculator
This calculator estimates the amount of electricity your solar panel system can generate based on three inputs:
- System Size (kW): This is the total rated capacity of your solar panels. For example, if you have 20 panels rated at 300W each, your system size is 20 × 0.3 = 6 kW.
- Sunlight Hours: This refers to the number of full-sun equivalent hours your location receives daily. A location may receive 12 hours of daylight but only 4–6 hours of "peak sun."
- System Efficiency: Real-world solar systems are not 100% efficient. Inverter losses, shading, temperature effects, and soiling reduce output. Typical efficiency ranges between 75–90%.
Calculation Formula
The calculator uses the following formula:
Daily Output (kWh) = System Size (kW) × Sunlight Hours × (Efficiency ÷ 100)
Monthly Output = Daily Output × 30
Yearly Output = Daily Output × 365
This provides an estimate under average conditions. Real output varies by season, weather, and maintenance.
Understanding Solar Output and System Performance
Your solar system’s actual output is affected by:
- Location: Latitude, climate, and elevation all impact sunlight availability.
- Roof Orientation & Tilt: South-facing roofs in the northern hemisphere produce the most energy. A tilt angle equal to your latitude is ideal.
- Shading: Trees, buildings, or obstructions can block sunlight and reduce efficiency significantly.
- Temperature: Higher temperatures reduce panel efficiency. Panels are rated at 25°C, but rooftop temperatures often exceed 40°C.
- Panel Degradation: Over time, panels lose efficiency. Most degrade 0.3–0.8% per year.
Example Scenario
Suppose you install a 6 kW solar system in an area with 5.5 average sun hours per day and 85% system efficiency:
- Daily: 6 × 5.5 × 0.85 = 28.05 kWh/day
- Monthly: 28.05 × 30 = 841.5 kWh/month
- Yearly: 28.05 × 365 = 10,235.25 kWh/year
With an average electricity rate of $0.13/kWh, that’s $1,330/year in energy savings.
Solar Sizing Tips
- Check your electric bill to find your average monthly kWh usage.
- Divide your monthly usage by 30 to get daily usage.
- Divide that by your region's sun hours to find required system size.
- Add 15–20% for system losses.
Common Sunlight Hours by Region
- Arizona (Phoenix): 6.5–7 hours/day
- California (Los Angeles): 5.5–6 hours/day
- New York: 4 hours/day
- Germany: 3.5–4 hours/day
- Dubai: 6.5 hours/day
- UK (London): 2.5–3.5 hours/day
Benefits of Knowing Your Solar Output
Understanding your estimated output helps you:
- Estimate payback time for your investment
- Right-size your system and avoid overpaying
- Compare performance against real-world results
- Optimize battery storage sizing (if applicable)
Frequently Asked Questions (FAQ)
Can I power my entire home with solar?
Yes, if your system is sized to match your energy usage and you receive sufficient sunlight. Adding batteries helps with night-time use or during outages.
How do I monitor my system’s performance?
Most modern inverters include a monitoring app or web portal showing real-time and historical output data.
What if I produce more power than I use?
With net metering, excess power is sent to the grid and credited to your account, offsetting future bills.
How accurate is this calculator?
It provides a reliable estimate under average conditions, but doesn’t account for shading, seasonal variation, or degradation. For detailed modeling, use tools like PVWatts or consult an installer.