Engineering Tools

W/m² to kWh/m² Converter & HSP

Master the difference between Power (Irradiance) and Energy (Irradiation). Convert meteorological units and calculate Peak Sun Hours for your sizing.

The units trap: Power vs. Energy

One of the most common mistakes in junior engineering is confusing W/m² with Wh/m². They are different physical quantities related by time.

⚡ Irradiance (G)

Unit: W/m² or kW/m²
Concept: Instantaneous power. It's the "force" with which the sun hits the panel in a specific second.
Analogy: Car speed (km/h) or tap flow rate (liters/min).

🔋 Irradiation (H)

Unit: Wh/m², kWh/m² or MJ/m²
Concept: Energy accumulated over a period of time (hour, day, year).
Analogy: Distance traveled (km) or water volume in a bucket (liters).

What are Peak Sun Hours (HSP)?

The sun doesn't shine constantly. It rises gently, reaches a peak at noon and decreases at sunset. To simplify calculations, we "compress" all that variable energy into a hypothetical rectangular block of 1000 W/m² (STC Conditions).

1 HSP = 1 kWh/m² of accumulated irradiation.

If a location receives 5.5 kWh/m² in a day, we say it has 5.5 Peak Sun Hours. This means we receive the same energy as if the sun had shone at maximum power (1000 W) for 5.5 hours.

Meteorological Data Conversion

Many scientific sources (like NASA POWER) deliver data in MJ/m² (MegaJoules). To use them in solar PV we must convert to kWh.

// Conversion factor

1 kWh = 3.6 MJ

// Example

20 MJ/m² ÷ 3.6 = 5.55 kWh/m² (HSP)

Need real irradiation data?

Stop estimating and start measuring. Access our database with irradiation history, TMY (Typical Meteorological Year) and production forecast for any coordinates.

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