Output (kWh per day) = panel kW × peak sun hours × 0.8. A 550 W panel at 4.8 sun hours produces about 2.1 units a day (about 63 a month). Each kW of panels produces about 3.8 units a day, or 3.4 to 4.6 depending on the city.
Step 1: Find Your Peak Sun Hours
Peak sun hours compress the day's changing sunlight into equivalent hours of full-strength sun (1000 W/sq. m.). Indian cities receive between 3.5 and 5.8: Jodhpur 5.8, Jaipur 5.5, Ahmedabad 5.3, Delhi and Hyderabad 5.0, Nagpur, Chennai and Bengaluru 4.8, Mumbai 4.5, Kolkata and Kochi 4.2, Shillong 3.5. Use your city, not a national average, because the spread changes output by up to 40%.
Step 2: Apply the Output Formula
The 0.8 is the performance ratio, which absorbs real-world losses (Step 3). Worked examples:
| Setup | City | Calculation | Daily Output |
|---|---|---|---|
| 1 × 550W panel | Nagpur (4.8) | 0.55 × 4.8 × 0.8 | 2.1 units |
| 3 kW system | Delhi (5.0) | 3 × 5.0 × 0.8 | 12 units |
| 5 kW system | Jaipur (5.5) | 5 × 5.5 × 0.8 | 22 units |
| 10 kW system | Kolkata (4.2) | 10 × 4.2 × 0.8 | 33.6 units |
Multiply daily output by 30 for monthly and 365 for annual figures, or let the solar generation calculator do it for your exact city.
How Much Electricity Does One Solar Panel Produce?
Daily and monthly output of a single panel at 4.8 peak sun hours (output = panel kW × 4.8 × 0.8):
| Panel | Units per day | Units per month |
|---|---|---|
| 100 W | 0.38 | 11.5 |
| 330 W | 1.27 | 38 |
| 400 W | 1.54 | 46 |
| 550 W | 2.11 | 63 |
| 620 W | 2.38 | 71 |
Sunny Rajasthan and Gujarat produce more; Kerala, the North-East and monsoon months produce less. Run your own city in the solar generation calculator.
Step 3: Understand the Losses Inside the 0.8
- Temperature: 8 – 12% on hot Indian roofs (cells run 55 – 65°C)
- Soiling: 3 – 8% with monthly cleaning, far worse if neglected
- Inverter conversion: 2 – 4%
- Wiring and mismatch: 2 – 3% (keep cables sized with the wire size calculator)
- Tilt/orientation: up to 10 – 15% if far from the ideal set by the tilt angle calculator
Step 4: Adjust for Season and Age
Monsoon months produce 30 – 40% below the annual average and summer above it, so judge a system on annual output. Panels also degrade about 0.5% a year: a system producing 4,200 units in year 1 still produces about 3,700 in year 25. For revenue projections, both effects matter; the savings calculator applies them automatically.
Month-by-Month Output Variation in India
The formula gives an annual average; real months orbit around it. Indicative pattern for north and central India (percent of the average month):
| Month | vs Average | Month | vs Average |
|---|---|---|---|
| January | ~95% | July | ~65% |
| February | ~105% | August | ~70% |
| March | ~115% | September | ~90% |
| April | ~118% | October | ~105% |
| May | ~115% | November | ~100% |
| June | ~90% | December | ~92% |
Coastal and eastern regions dip harder in monsoon (down to 55 to 60%), while Rajasthan flattens the curve. Judge any calculated monthly figure against the season it belongs to before concluding anything about the system.
Checking a Real System Against the Calculation
Read your inverter's daily kWh log or your net meter, average over a full month, and compare with the formula result. Consistently landing more than 15% below the estimate points to soiling, new shading, an under-performing string or an inverter issue worth a service call. Panel-level specs can be sanity-checked with the efficiency calculator and the wattage calculator.