With the shading simulation, autarc calculates for every sun position of the year how much of each panel is in shade. You see the shadows at any time of day, the loss per panel and how much yield each object costs.
The result feeds directly into the yield, the simulation and the proposal presentation. To learn how autarc calculates the yield, see How is the PV yield calculated?
Requirements
autarc can only calculate shadows from objects that exist in the design. Model the surroundings in one or more of these ways:
Draw objects: e.g.
Tree,Obstruction(such as a chimney with a height),Fence,Wall,Carportor further roofs and dormers. Give each a realistic height.3D Terrain: On map providers, hills, neighbouring buildings and trees from the terrain data then cast shadows too.3D model: Everything contained in the model casts shadows, e.g. from the photogrammetry service.
Shading from the far horizon, e.g. mountains, is always included via PVGIS.
The shading simulation is not available with perspective photos. In a by-numbers planning, enter Shading losses (%) per PV array instead.
Starting the shading simulation
In the
Systemsidebar, clickShading.Switch on
Shading Simulation.Wait until
Calculating shading…has finished. The progress is shown below.
autarc then shows the Shade loss of all panels as a percentage of the yearly yield and in kWh, e.g. “0.8 % · 94 kWh”. You also see the loss directly in the Shading row of the sidebar.
If you change panels or objects, autarc recalculates automatically.
Tip: Under Settings > Products > PV-Planning, use Enable shading simulation by default to switch the simulation on for every new solar design.
Note: While the shading simulation is on, autarc recalculates after every change to panels or objects. On older or slower computers this can slow down the solar design. If so, switch the simulation off while drawing and back on for the analysis.
Viewing shadows over the day
By default, autarc shows the Yearly average. With Hourly, you see the shadows at a specific moment:
Date: Move the slider through the year, e.g. to 21 December, when the sun is at its lowest.Time of day: Move the slider through the day. The shadows on the canvas follow the position of the sun.Sun Path: shows the path of the sun above the design.
This lets you show your customer, for example, when the tree in the garden reaches the roof.
Shading per panel
With Panel Shading, autarc shows a percentage on each panel and colours it accordingly:
Yearly: the share of the yearly yield that shade costs this panel. The values are energy-weighted and therefore comparable with other tools such as PV*SOL. Below 1 %, autarc shows one decimal in smaller type; from 1 %, whole percentages.Hourly: the share of the panel area that is in shade at the selected hour.
This way you spot heavily shaded panels at a glance. It is often worth removing them or moving them elsewhere.
Shading and stringing
Shade doesn't only cost yield on the shaded panel. The panels of a string carry one current, so one shaded panel can hold back the whole string. autarc shows both losses separately, so you can see what the shade costs and what your stringing costs.
Below Panel Shading, you switch between:
Shading: the loss from the shade on the panel itself. It doesn't change when you rewire strings.Stringing: the extra loss because the panels of a string carry one current.
The info icon next to it explains both values for the selected view. Below are two lines; the line of the selected view is highlighted:
Shade loss, e.g. “0.8 % · 94 kWh”Stringing loss, e.g. “1.1 % · 133 kWh”. This line only appears once at least one string has been created.
In Hourly mode, the values apply to the selected hour. At night, both lines show 0 % · 0 kWh.
Stringing loss per string and inverter
In the sidebar, strings and inverters show their Stringing loss. In a string's details, autarc names the causes and suggests fixes, e.g.:
Shade spreads along the string: with a suggestion on which panel a DC optimizer would gain how much.Mixed orientations in one string: with the suggestion to remove the panels facing the other direction.Tracker stays on a lower peak: when the inverter has no shade management.String voltage leaves the MPP rangeandParallel strings of different length.
You set how the inverter handles partial shade under MPP tracker under shade. By default, the Shade management value from the inverter's product data applies.
With Find recommended optimizers, autarc calculates on which panels a DC optimizer pays off. With Place recommended optimizers, autarc places them directly. This requires a DC optimizer in your products.
Panels without a string are calculated with ideal stringing.
Shade map
The Shade map lays a colour layer over the roofs. It shows the yearly average and helps you find the best areas before any panels are placed:
Shading: how strongly each spot is shaded.Irradiance: how much sun each spot receives over the year, including shading, orientation and tilt.
How much yield does each object cost?
Select an object, e.g. a tree. In its details in the sidebar, autarc shows under Removing this would gain how much yield per year you would gain without this object, in kWh and as a percentage. If the object casts no shadow on the panels, the value isn't shown.
This is a strong argument in a customer conversation, e.g. for cutting back a tree.
Shade Report
Under Shading, click Show report to open the Shade Report. You also find it in the project's technical documentation. It contains:
Summary: includingYearly production,Specific yield,Shading losses,Sun availability,TOFandTSRF.Per array: the same values for each group of panels with the same orientation and tilt.Sun availability per month: the share of the unshaded monthly yield that remains after shading.Shading objects: the yield lost to each modelled object.Site views: images of the panel shading and the irradiance.Sun path diagrams per array with the horizon from PVGIS and your objects, including the MCS shade factor.
With the stringing analysis, the report also contains:
Yield from potential to plan: every kWh between the unshaded potential and the planned yield, by cause, e.g.Shaded area,Mixed orientations in strings,Shade spreading along stringsandRecovered by DC optimizers.Stringing yield per string: what each string loses compared with its panels producing on their own. Below 2 % is good, above 5 % is critical.DC optimizers: the yearly yield without optimizers, as planned, only on the recommended panels and on all panels.
Use Download PDF to save the report. In the technical documentation, you can also add it as a section to the full report.
Key figures in the report
TOF(Tilt and Orientation Factor): how good the orientation and tilt are compared with the optimal orientation at the site.Sun availability: the share of sunlight that reaches the panels after shading.TSRF(Total Solar Resource Fraction): both combined, i.e. the share of the optimally possible irradiance that actually arrives.
Frequently asked questions
Why is the sum of the object losses greater than the total loss?
Each value applies to removing that one object. If two objects shade the same panel, each carries the full shared loss. So the values can't be added up.
Why does the report say “Shading not assessed”?
The shading simulation was not completed for this design, so the values equal the unshaded yield. Open the design, switch on Shading Simulation and wait until the calculation has finished.
Why don't I see any shading although there's a tree next to the house?
Check that the tree is drawn in the design and that its height is correct. On map providers, 3D Terrain also helps. Without an object, autarc can't calculate a shadow.
Why do the panel values differ from PV*SOL?
In the yearly average, autarc shows the share of the yearly yield that shade costs a panel. This matches how PV*SOL presents it. Small differences come from different weather data and models of the surroundings. In Hourly mode, autarc instead shows the shaded share of the area at one hour, which can be considerably higher.