Let’s break down the Incident Radiation component in Ladybug, and the meaning of those Minimum = 0 kWh/m² and Maximum = 1000 kWh/m² values.

🔹 What the component does

The Incident Radiation component in Ladybug calculates the solar radiation (irradiance integrated over time → irradiation/insolation) that falls on a geometry’s surfaces.

Units: kWh/m² (kilowatt-hours per square meter).

It considers direct radiation, diffuse radiation, and reflected radiation based on the EPW weather file.

Output is usually a colored mesh mapped on the geometry to show which areas get more or less solar energy.

🔹 The legend range (Min & Max)

Ladybug visualizations always normalize the results into a legend range. By default:

Minimum = 0 kWh/m²

→ the lowest possible value of incident solar radiation. A surface that never receives sun (like a north-facing façade in winter, or a fully shaded surface) will be colored at this end.

Maximum = 1000 kWh/m²

→ the upper cap of the legend. If a surface receives a lot of radiation (like a roof or south façade), it will be close to this value.

This 1000 kWh/m² is not a physical limit, but a convenient visualization range. It’s chosen because:

Typical annual solar irradiation on vertical/horizontal surfaces is between 200–1200 kWh/m², depending on location and orientation.

1000 kWh/m² is a good “round” upper bound for most climates.

If you’re in a very sunny region (e.g., Middle East, southern Spain, Dubai), you may want to increase the maximum (like 1200–1500 kWh/m²).

If you’re in a cloudy region (e.g., Belgium, UK), you could lower it to ~700–800 kWh/m² for better contrast.

🔹 Why not auto-scale?

Ladybug allows you to set the legendPar_ input (Legend Parameters). If you don’t, it uses defaults (0–1000).

Auto-scaling (min = actual min, max = actual max) can sometimes exaggerate results, making tiny differences look huge.

Fixed scales (0–1000) let you compare different designs consistently. For example, comparing shading strategies across options is only valid if the legend range is identical.

🔹 Practical takeaway

0 kWh/m² = No sunlight at all.

1000 kWh/m² = Very sunny spot (like a roof in a sunny climate).

The range is a visual normalization tool, not an absolute physical law.

You can always change it via Legend Parameters if you need higher accuracy or climate-specific scaling.