1 152 sun positions per year
For each month we take one typical day and compute the sun's position every 15 minutes: 96 steps per day, 12 × 96 = 1 152 positions for the year. At every step the model knows where the sun stands over your house and how much light arrives as a direct beam and as diffuse light from the sky. A panel's light at that step is the beam when the sun is visible from the panel, plus the diffuse part scaled by how much open sky the panel sees. Light that hits at a flat angle counts for less, as on a real module.
The 15-minute step belongs to the sun and shade model. The household, the battery, the car and the prices then run hour by hour over all 8 760 hours of the year.
Three things cast shade
Three kinds of objects block the sun in the model: the house itself (a wing, a dormer or a second storey shades a lower face), roof objects, and trees. Roof objects such as chimneys, vents and skylights are solid blocks with a footprint and a height: a chimney is 1.2 m above the roof, a vent 0.4 m, a skylight 0.2 m and a dormer 1.5 m unless you set another height. Panels are placed clear of every roof object with a margin, so a chimney costs shade, not panels.
A tree is a trunk and a crown. The crown lets 15 % of the light through, in every month of the year, so a birch in winter is treated like a spruce: the estimate errs on the shaded side.
Trees as the AI sees them, and as you correct them
An AI model marks the trees around the house on the aerial photo and gives each one an estimated height and crown. You can move a tree, change its height or crown radius, copy it, or add one by tapping the map: a new tree gets a 3 m crown and a height of 6.6 m, and height and crown stay linked at 2.2 to 1 until you set them apart. A tree can stand up to 60 m from the middle of the house and a model holds up to 30 trees.
The estimate shows the shade loss as a share of the year's production and splits it by cause: trees, roof objects and the house.
The Radiance view
The Radiance view colours every roof face by the sunlight it receives, in kWh per square metre per day, on a 0.5 m grid. You can switch between any month and the whole year; a dark month such as December gets its own colour scale so it stays readable. Each panel carries its own production per day, and the panel labels add up to the same yearly kWh as the estimate: the map and the saving come from one calculation.
The side panel lists, per roof face, the production, the irradiation, the best and the worst panel, and a 12-month curve with and without shade.
Weather from PVGIS, read at your house
Sunlight and temperature come from PVGIS 5.3, the European Commission's satellite-based record, as monthly irradiation, diffuse share and temperature on a grid of about 25 km over Sweden. We interpolate the four nearest grid cells at your house and lay the month's irradiation onto a daily sun curve. One typical day stands in for each month, so one cloudy week averages out; a year with more or less sun than the long-term record moves the result with it. The data is © European Union, CC BY 4.0.
