The chart shows the average daily insolation on flat ground for the selected hour of day, by month of the year. Insolation for the given hour of day varies as the sun's path changes with the seasons.

What does it tell me?

• How the amount and intensity of sunlight varies across the year at specific hour of the day
• e.g. will the sun shine through the bedroom window between 7 and 8 in morning?
• e.g. will the garden patio be in the shade in the late afternoon in summer?

Note: the chart does not account for shade from structures or objects (e.g. buildings or trees) or cloud cover.

Insolation is a measure of the power of sunlight reaching a surface. It is usually given for a period of time, e.g. per hour, per day, per month.

Horizontal insolation is a good measure of the overall sunlight potential for the location. The direction in which you are facing does not affect its value.

Generally, you will see higher 'horizontal' (i.e. flat ground) insolation in summer months, and lower values during winter months. Latitudes closer to the equator and those lying at higher elevations typically see higher insolation values.