Solar Generation Calculator
Want to know how much electricity your solar panels will actually produce? Use this free solar generation calculator to estimate daily and monthly units (kWh) from your system.
Enter your solar system size in kW and the average sun hours in your city. The calculator instantly shows realistic production figures so you can see if a 5 kW or 10 kW system will meet your needs.
How This Calculator Works
The calculator uses this formula:
Daily Generation (kWh) = System Size (kW) × Sun Hours × 0.8
Monthly generation is simply Daily × 30.
The 0.8 factor accounts for real-world losses.
What Each Number Means:
| Factor | What It Means |
|---|---|
| Solar System Capacity (kW) | Size of your solar system (e.g. 5 kW, 10 kW) |
| Average Daily Sun Hours | Peak sunlight hours per day in your city |
| 0.8 Derate Factor | Accounts for heat, dust, wiring and inverter losses |
Why We Use the 0.8 Derate Factor
Solar panels never produce 100% of their rated power in real conditions. The 0.8 factor (20% loss) covers:
- Heat losses : panels become less efficient in Pakistan’s hot summers
- Dust and dirt : very common, especially in Punjab and Sindh
- Inverter and wiring losses
- Not-perfect panel angle or shading
This gives you a more realistic estimate instead of an overly optimistic number.
Example Calculation
Let’s say you have a 5 kW solar system in Lahore (4.5 sun hours).
5 × 4.5 × 0.8 = 18 kWh per day
18 × 30 = 540 units per month
Result: A 5 kW system would produce approximately 18 units daily and 540 units monthly under average conditions.
Factors That Affect Real Generation
- Roof direction and tilt (south-facing is best in Pakistan)
- Shading from trees, water tanks or nearby buildings
- Panel quality and age
- Seasonal changes (winter production is lower)
- Cleaning frequency (dust can reduce output by 15–25%)
This calculator provides estimates based on average conditions in Pakistan. Actual solar generation varies depending on your exact location, weather, roof orientation, shading, equipment quality and maintenance.
These results should be used for initial planning only. Always consult a certified solar installer for a professional site assessment before making a purchase decision.