Solar Shading Analysis Software Ireland: 2026 Guide

Irish solar shading analysis has a counterintuitive property: most tools overstate the loss. In a cloudy maritime climate a large share of annual irradiance arrives as diffuse light scattered across the whole sky, not as a direct beam from the sun’s position. A shading model that traces a geometric shadow and writes off everything inside it is describing a desert. On an overcast Dublin afternoon a module sitting in geometric shadow is still collecting most of the light an unshaded module collects. This guide covers what shading analysis has to do differently in Ireland, and which tools do it properly.

Short version. Solar shading analysis software for Irish projects has to model diffuse and direct irradiance separately, run 8,760 hourly steps at module level, and price the resulting loss against the gap between Irish retail rates and Clean Export Guarantee rates. A single annual shading percentage produced by a geometric shadow trace is the wrong output twice over: wrong in magnitude, because it ignores diffuse, and wrong in usefulness, because it does not say which hours were hit.

The general methodology is covered in our solar shading analysis software guide. This page covers what changes in Ireland. For the wider platform comparison see best solar design software Ireland.

Why Geometric Shading Models Overstate Irish Losses

A shading engine has to answer two separate questions for every module in every hour. Is the direct beam from the sun’s current position blocked? And how much of the sky dome, from which diffuse light arrives, is obscured?

In a clear-sky climate the first question dominates, because most of the energy is in the beam. In Ireland it does not. Diffuse light arrives from the whole visible sky, so an obstruction that completely blocks the sun still leaves the module receiving light from every part of the sky the obstruction does not cover.

The practical consequence is a systematic bias. A tool that answers only the first question reports a shading loss that can be substantially higher than the real one, and the error is largest exactly where Irish designers need accuracy: modest obstructions on modest roofs, where the difference between a 9% loss and a 6% loss decides whether the project is sold.

Latitude: Long Shadows That Often Cost Little

Ireland sits above 51 degrees north, with Dublin near 53. Shadow length scales inversely with the tangent of solar altitude, so Irish winter shadows are long.

Here is where Ireland diverges from Canada, which has similar geometry. Those long Irish winter shadows fall across hours that are both dim and heavily diffuse, so the energy behind them is small and the shadow itself is soft. The same table in a continental climate with clear cold winters describes a serious loss. In Ireland it mostly describes a dramatic-looking diagram attached to very few kilowatt-hours.

That is why the annual weighting matters more than the worst-case geometry. The hours that carry Irish generation are bright spring and summer days, and shading analysis should be judged on how well it handles those.

Chimneys, Dormers And Why Manual Estimation Fails

Irish residential roofs are awkward. Older housing stock carries more chimney stacks than newer markets, those stacks are often tall enough to shade a meaningful area, and terraced and semi-detached rows put neighbouring gable ends close to the array. Add dormers, hips, valleys and mature garden trees and very few Irish roofs present a single clean obstruction.

Manual estimation handles one obstruction acceptably and multiple interacting obstructions badly, because shadows overlap and move at different rates through the day. The failure is not a small percentage error. It is that the installer picks a string layout that puts modules affected by different obstructions on the same string, and the series constraint then propagates each shadow further than it needs to go.

This is the argument for module-level modelling in Ireland, and it is an argument about layout rather than about reporting. The point of knowing which modules are shaded in which hours is to wire the array so that the shadows do not compound. Our 3D solar design software guide covers the modelling side of this.

Pricing The Loss Against The Clean Export Guarantee

Irish retail electricity is expensive and Irish export compensation is not. Under the Clean Export Guarantee, exported units are paid at a supplier-set rate that sits well below the import price a household pays.

That gap creates a strong asymmetry in what shading costs:

• A shaded kilowatt-hour that would have been self-consumed costs full retail. This is the expensive case.
• A shaded kilowatt-hour that would have been exported costs only the export rate. This is comparatively cheap.

So the financial cost of an obstruction depends on when its shadow falls relative to household demand. A chimney that shades the array between eleven and two, when a typical unoccupied house is exporting almost everything, destroys cheap kilowatt-hours. A tree that shades the array from four in the afternoon, as the household comes home and demand rises, destroys expensive ones.

Two obstructions with identical annual shading percentages can therefore differ by a factor of two or more in what they actually cost. No geometric tool can distinguish them. It requires an hourly simulation that carries a load profile alongside the generation profile, which is also the calculation that decides whether battery storage is worth adding. Our best solar design software Ireland guide covers the tariff and grant side in full.

Worked Example: Chimney On A Dublin Semi

An illustrative calculation showing the gap between modelling methods, not a specific customer project. Inputs: 4 kW array on a south-west facing slope, a single 1.8 m chimney stack on the same slope, and a household that exports most midday generation.

The first row is what a shadow-trace tool reports and it is wrong by a wide margin. The second row is the honest baseline. The third row costs nothing but attention, and it is the single highest-return change on this roof. The fourth row costs hardware, and on a 4 kW Irish array the extra 1.4 percentage points recovered has to be weighed against that cost rather than assumed to justify it.

The lesson for quoting is that two of the four rows are free. Choosing a better engine and wiring the array with the shadow map in front of you recovers more than half the apparent loss before anyone sells a single optimiser.

Who Should Choose What

• Choose SurgePV if you want 8,760-hour module-level shading with a separated sky model and Irish tariff pricing in one tool.
• Choose PVsyst where a lender or a large commercial client names it, and for detailed research-grade sensitivity work.
• Choose HelioScope for commercial rooftop engineering where the customer document is produced elsewhere.
• Avoid pure geometric shadow tools. In Ireland they overstate losses and cost you projects that were viable.

The Bottom Line

Irish shading analysis is a sky-model problem before it is a geometry problem.

• Use an engine that splits direct and diffuse. Geometric-only tools systematically overstate Irish losses and kill viable projects.
• Fix the string layout before selling hardware. On complex Irish roofs, wiring around the shadow map is free and recovers more than most people expect.
• Price the loss against the export gap. Shading that hits self-consumed hours costs several times more than shading that hits exported surplus.