Calculating solar energy production using raw irradiance data requires complex integration (Calculus). However, field technicians use a powerful simplified metric called Peak Sun Hours (PSH).
PSH essentially compresses all the sunlight received during the day (which varies in intensity) into a hypothetical number of hours where the sun shines at full strength (1,000 W/m² or 1 kW/m²). The formula is simple:
PSH = Daily Irradiation (kWh/m²) / 1 kW/m²
For example, if a site in Jaipur receives a total daily irradiation of 5.4 kWh/m², we say it has 5.4 Peak Sun Hours. This makes system sizing incredibly easy. If you have a 1 kW solar system, you can estimate its daily generation by simply multiplying the system size by the PSH:
1 kW System × 5.4 PSH = 5.4 kWh per day.
While this doesn’t account for system losses (like heat, dust, or cable resistance), it provides a very quick and reasonably accurate “rule of thumb” for feasibility studies. It helps customers understand that even if the sun is up for 12 hours, they might only get 4-5 “Peak Sun Hours” of equivalent generation.
