Solar Shading Analysis Software in Italy: Top 10 2026

If you are choosing solar shading analysis software Italy designers can defend in 2026, latitude is the least of your problems. Rome sits at 41.9 degrees north, which puts the December sun at nearly 25 degrees and makes inter-row spacing comparatively easy. What makes Italian shading hard is where Italian PV actually goes: onto hillsides where the ground itself tilts the whole geometry, into dense historic centres where a five storey neighbour across a four metre street decides the winter yield, and onto the roof plane the Soprintendenza will permit rather than the roof plane the sun prefers. That last one is a design compromise with a price in kWh, and pricing it is exactly what a shading tool is for. The platform that wins our 2026 bench is SurgePV at roughly €1,180 (US$1,299) per user per year on the 5-User Team plan, and ACCA Solarius-PV, the genuine Italian incumbent, is handled honestly below rather than waved away. Ten tools, priced in euros, with named weaknesses on each including ours.

Direct answer. The best solar shading analysis software for Italy in 2026 is SurgePV, at about €1,180 per user per year on the 5-User Team plan, because it runs an 8,760-hour module-level shading simulation with bypass-diode physics, models terrain slope and neighbouring building volumes from satellite, and lets you price a heritage-constrained roof position against the ideal one in kWh and euros. PVsyst remains the format an Italian bank’s technical adviser asks for by name, and ACCA Solarius-PV remains the tool that fits the Italian document set.

This guide is for installatori, studi di progettazione and EPC design teams whose yield numbers get challenged. It sits under our global pillar on solar shading analysis software and alongside the wider solar design software Italy ranking, which covers the full design workflow rather than shading alone.

Why Italian Shading Is a Terrain and Building-Stock Problem

Three site conditions dominate Italian shading work, and none of them is about how far north you are.

The ground is not flat. A large share of Italian rooftop and small ground-mount PV sits on slopes: hill towns across Toscana, Umbria and Marche, terraced agricultural land in Liguria and Campania, alpine and pre-alpine valleys in the north. Slope changes the shading arithmetic directly, because what matters for row spacing is the sun’s elevation relative to the ground plane, not relative to the horizontal. A south-facing slope adds its angle to the effective sun elevation and shortens every shadow. A north-facing slope subtracts it and lengthens every shadow. The numbers are in the next section and the swing is larger than most designers expect.

The building stock crowds itself. Italian urban form is dense, vertical and old. In a centro storico the dominant obstruction is not a chimney on your own roof, it is the palazzo across a street that is four metres wide and four storeys taller than the roof you are working on. A building of that height at that distance blocks the sun below roughly 45 degrees of elevation from that direction, which in Rome removes most of the winter day from the north side of the array and a meaningful part of the shoulder seasons. Courtyard buildings shade themselves. Party walls and torrette shade the neighbours. None of this is exotic, but it is geometry that satellite-only modelling handles poorly and that a designer standing at street level cannot estimate accurately.

The permitted roof plane is not always the good one. This is the part that separates Italy from most markets. Under the Codice dei beni culturali e del paesaggio, D.Lgs 42/2004, large areas of Italy carry a vincolo paesaggistico or fall inside a protected centro storico, and works in those areas need an autorizzazione paesaggistica from the competent authority with the Soprintendenza involved. Recent national simplifications have made rooftop PV substantially easier in many contexts, but in constrained zones the practical outcome is often a condition on visibility: the array must not be visible from a public viewpoint, or must sit below a ridge line, or must go on the rear or courtyard pitch rather than the street-facing one. That permitted position is frequently the shaded one. The design question stops being “where does the sun want the panels” and becomes “what does the permitted position cost, and is the project still worth building”.

Put those three together and the Italian requirement is specific: a shading tool has to handle terrain slope, tall close obstructions, and comparative scenarios, because half the real work is showing a client the difference between two positions rather than the loss of one.

Shadow Geometry from Palermo to Milano

Solar noon elevation at the winter solstice is 90 minus site latitude minus the earth’s axial tilt of 23.44 degrees. Shadow length is object height divided by the tangent of that elevation. Run it down the peninsula.

City	Latitude	December solar noon	Shadow multiple	GCR at 30° south, flat
Palermo	38.1° N	28.5°	1.85x	0.56
Rome	41.9° N	24.7°	2.18x	0.51
Milan	45.5° N	21.1°	2.60x	0.46
Bolzano	46.5° N	20.1°	2.74x	0.45
Berlin (reference)	52.5° N	14.1°	3.99x	0.35

Two readings matter here. First, Italy is not one number. A 2 m parapet casts a 3.7 m December-noon shadow in Palermo and a 5.2 m shadow in Milan, a 40 percent difference inside one country, and the resulting ground coverage ratio moves from 0.56 to 0.46. A single national spacing default is wrong at both ends: too sparse in Sicily, too dense in Lombardia. Second, and this is the point Italian installers should take from the whole section, Italy is nowhere near Germany. Tooling whose defaults assume a 4.0x shadow multiple will hand you a GCR near 0.35 on a Roman flat roof that comfortably supports 0.51, which is roughly 45 percent more kWp on the same mounting footprint.

Now the slope correction, which is the genuinely Italian part. What sets row spacing is the sun’s elevation measured against the ground plane. On a slope of angle β the effective elevation is the solar elevation plus β for a south-facing slope, and minus β for a north-facing one. Take Rome and a modest 10 degree hillside:

• 10 degree south-facing slope. Effective elevation 34.7 degrees, tangent 0.692, shadow multiple 1.45x. A 0.567 m row casts 0.82 m, plus 0.98 m of row depth, giving a 1.80 m pitch and a GCR of 0.63.
• Flat ground. Multiple 2.18x, pitch 2.22 m, GCR 0.51.
• 10 degree north-facing slope. Effective elevation 14.7 degrees, tangent 0.262, shadow multiple 3.82x. The same row casts 2.17 m, giving a 3.15 m pitch and a GCR of 0.36.

A ten degree slope is nothing. You would barely notice it walking up it. It moves the achievable ground coverage ratio by a factor of 1.75 between the two aspects, which means a terrain-blind tool will either over-space the south-facing site and lose a third of the capacity, or under-space the north-facing one and put the client’s winter mornings into permanent self-shading. On real Italian hillside sites the slope is often steeper than ten degrees and rarely faces due south, so azimuth interacts with it too.

Key takeaway. In Italy the shading question is set by the site rather than by the calendar. Slope aspect can swing the achievable ground coverage ratio from 0.36 to 0.63 at the same latitude, a tall neighbour across a narrow street can remove most of the winter day, and a heritage condition can put the array on the wrong pitch entirely. All three are geometry a tool either models properly or guesses at.

What a Vincolo Paesaggistico Actually Costs in kWh

This is the section that turns a permitting conversation into an engineering one, and it is the most useful thing an Italian shading tool can do for you.

When a heritage condition moves an array off the street-facing south pitch onto the courtyard-facing north-east pitch, or holds it below a ridge, or restricts it to a portion of the roof out of public view, the client is being asked to accept a worse energy outcome for a permitting reason. That is a legitimate trade, but it should be a priced trade. The honest deliverable is a comparison: the unconstrained layout, the permitted layout, and the difference in annual kWh, in self-consumption fraction, and in payback years.

The reason this needs a real shading engine rather than a rule of thumb is that the two losses compound. The permitted position usually carries both an orientation penalty, because it faces the wrong way or sits at the wrong tilt, and a shading penalty, because the position that is invisible from the street is frequently the position the building’s own volume or the neighbour’s overshadows. Adding an orientation factor to a shading factor understates the combined effect, because shading is non-linear at module level and the shaded hours on a poorly oriented plane are disproportionately the few good hours it had.

Three practical outputs are worth building into the proposal:

1. Side-by-side annual yield for both positions, run at 8,760-hour module level, not as two orientation factors applied to the same gross figure.
2. The self-consumption fraction for each. Since Scambio sul Posto closed to new systems, exported energy earns a wholesale-linked Ritiro Dedicato price while self-consumed energy avoids a full retail bill. A permitted position that loses morning production on a household that consumes in the morning costs far more than the kWh delta suggests.
3. A mitigation option priced against both. Module-level electronics, a re-cut string plan or a smaller but better-placed array frequently recovers a good share of the difference, and the client can only judge that against a number.

Our proposal software ranking for Italy covers how that comparison reaches the customer document, and the shading loss glossary entry sets out the electrical mechanism behind the non-linearity.

CER Shading: A Coincidence Problem, Not an Allocation Problem

Comunità Energetiche Rinnovabili create shared generation, as Spanish autoconsumo colectivo does, but the legal shape is different and so is what shading does to it.

In a Spanish colectivo, production is divided between participants by reparto coefficients, so a shading loss is fundamentally an allocation question: whose kWh disappeared. In an Italian CER nothing is allocated. Every member keeps their own supply contract and draws normally from the grid, and the incentive is paid on shared energy, defined as the hourly overlap between what members produce and what members consume inside the area served by the same primary substation. Nobody owns a slice of the array’s output. The community earns on coincidence.

That changes the shading question completely. A shading loss in an hour when member consumption already exceeds member production reduces shared energy euro for euro, because every lost kWh was being matched. A shading loss in an hour when production already exceeds consumption may reduce shared energy by nothing at all, because the surplus was not being matched anyway and only ever earned a Ritiro Dedicato price. So the same geometric shadow can be expensive or nearly free depending on the aggregate load shape of the community in that hour, and you cannot know which without hourly member consumption data.

The practical consequence for tool selection is narrower than it sounds. What a CER designer needs from the shading tool is an hourly shaded production series per member site, exported cleanly, so it can be fed into whatever energy-sharing model does the community arithmetic. An annual shading percentage is useless to that workflow. A monthly profile is barely better. If the tool cannot export 8,760 shaded values per site, the community model is being built on a smoothed input and its shared-energy estimate is soft.

We should be plain about the limits here. No general-purpose PV design tool on this list, ours included, performs portfolio-level shared-energy optimisation across a whole community. In 2026 that arithmetic is still done in a separate CER platform or a spreadsheet. What the shading tool owes you is a clean, honest, hourly input to it, and most tools do not export one.

Top 10 Shading Analysis Tools in Italy Compared

Pricing is 2026, annualised, with dollar-denominated products converted at roughly €0.91 per US dollar. Treat converted figures as indicative and confirm with the vendor.

#	Tool	Price, vendor’s billing currency	Shading capability	Best for
1	SurgePV	US$1,299/user/yr on the 5-User Team plan (~€1,180)	8,760-hr module-level with bypass diodes, terrain and neighbour volumes from satellite	Installatori comparing constrained roof positions
2	PVsyst	CHF 700/user/yr Professional, annual subscription	Near-shading plus horizon file, documented loss tree	Bank advisers, agrivoltaico, ground mount
3	ACCA Solarius-PV	Not publicly listed	Competent 3D shading tied to the Italian document set	Studi delivering a relazione tecnica
4	PV*SOL premium	EUR 845 per named user per year plus VAT	Animated 3D walkthrough, best client artefact	Selling a constrained layout in the meeting
5	HelioScope	US$159/mo Basic, US$259/mo Pro (~€145 to €236)	Module-level C&I simulation with a clean loss tree	Capannoni and consultancies
6	Scanifly	Not publicly listed	Drone photogrammetry to measured 3D geometry	Centri storici and tall close neighbours
7	Solmetric SunEye 210	US$2,195 base, North America (~€2,000)	Measured fisheye horizon at a physical point	Disputes and heritage-constrained sites
8	PVGIS horizon import	Free	Terrain horizon profile fed into another engine	Alpine valleys, hill towns, Appennini
9	Polysun	Not publicly listed	Shading inside a coupled PV and heat pump model	Renovation and sector coupling
10	Aurora Solar	US$135/user/mo Basic, US$220 Premium, billed annually (~€123 to €200)	Strong residential shade rendering, gated on Premium	Multinationals already on Aurora

Note the difference from our design software ranking for Italy, where ACCA Solarius-PV places second. On shading specifically it places third. Its shading is competent and well integrated, but it is not at PVsyst’s level for near-shading depth or horizon handling, and that is the axis this page ranks on. Positions 6, 7 and 8 are measurement inputs that feed the others rather than competitors to them.

1. SurgePV

What it does best. SurgePV runs an 8,760-hour shading simulation at module level with bypass-diode physics on every paid plan, which matters because shade is non-linear and array-level averaging hides the loss that shows up on the meter. For Italian work the useful part is what it does with site geometry. It builds the 3D roof from a satellite address in about a minute, picks up neighbouring building volumes and terrain rather than assuming a flat plane, and lets you duplicate a project to run the unconstrained layout against the heritage-permitted one and compare annual kWh, self-consumption fraction and payback side by side. That comparison is the deliverable an autorizzazione paesaggistica conversation actually needs. The per-module annual loss heatmap drives string and MPPT grouping, hourly shaded production exports cleanly for a CER sharing model, and the result flows into the CEI-labelled single-line diagram and the Italian offerta without a re-import.

Pricing. €1,180 (US$1,299) per user per year on the 5-User Team plan, so €5,900 for five seats. Individual seats about €1,730 per year. Free trial, no credit card.

Who it suits. Installatori and EPCs at five or more designs a month, especially anyone regularly working in constrained centri storici or on hillside sites.

Honest limitations. Four concrete ones, and in Italy two of them bite. It cannot import a measured horizon file from a Solmetric SunEye or a fisheye photograph, so on a hill town under a ridge you rely on modelled terrain rather than a reading somebody took on the roof. It has no drone photogrammetry ingest, and satellite imagery is at its weakest exactly where Italy is hardest, which is a narrow street with tall facades where building heights and overhangs are poorly resolved from directly above. It does not perform portfolio-level CER shared-energy optimisation, so community arithmetic stays outside the tool. And it produces no computo metrico estimativo priced against a regional prezzario, which is the single strongest reason an Italian studio keeps ACCA regardless of what else it buys.

Book a SurgePV demo and bring a genuinely awkward site, a hillside or a courtyard, because a clean detached roof tells you nothing about a shading engine.

2. PVsyst

What it does best. PVsyst is the reference. Its near-shading model, its separate far-horizon handling, its electrical shading loss treatment and its documented loss tree are what everything else is benchmarked against, ours included. For Italy the horizon handling deserves specific mention, because on an Appennini or alpine site the terrain horizon frequently costs more winter energy than every object on the roof combined, and PVsyst treats far horizon and near shading as separate, properly modelled things. On financed work the technical adviser asks for a PVsyst report by name, and on that axis it beats SurgePV outright. Heaven Designs published a walkthrough of how to read a PVsyst loss diagram if you have to defend one line by line.

Pricing. PVsyst bills in Swiss francs and it is an annual subscription rather than a perpetual licence: CHF 700 per user per year for the Professional edition, with Education at CHF 420, Training and Research at CHF 560, Student and Classroom at CHF 25, and PVsystCLI at CHF 3,000. Group discounts run 5 to 20 percent by quantity. Five Professional seats are CHF 3,500 a year, which is plainly cheaper than five SurgePV seats at US$6,495, and worth saying out loud even though we sell the more expensive product.

Who it suits. Independent engineers, due diligence teams, and agrivoltaico and ground-mount developers in the south.

Honest limitations. Windows desktop, a steep learning curve, and slow manual construction of the 3D scene, which is painful precisely on the dense urban geometry Italy throws at you. No CEI documentation, no proposal, no Italian incentive modelling, and no comparative scenario workflow that a client would recognise. See our PVsyst alternative comparison and the head to head on HelioScope versus PVsyst.

3. ACCA Solarius-PV

What it does best. ACCA is the dominant technical software house in Italian construction, based in Montella, and Solarius-PV carries a competent 3D shading model that is properly wired into the rest of the Italian deliverable. You place the surrounding volumes, it computes the shading effect on the array, and the result lands inside the relazione tecnica and the schema elettrico that go into the building file, then on into the computo metrico. For a studio whose product is that document set, having the shading number generated in the same environment rather than transcribed from a second tool is worth real time and removes a class of transcription error.

Pricing. Not publicly listed. ACCA’s own Solarius-PV page shows no price for the software, only a EUR 599 POWER PACK upgrade and a phone number for its commercial office. Ask for a quote against the module set you actually need, and confirm whether the figure is an annual subscription or a one-off purchase.

Who it suits. Studi di progettazione, geometri and periti industriali whose deliverable is a document set rather than a sales proposal.

Honest limitations. On shading specifically it is not the deepest tool here, which is why it ranks third on this page and second on our design page. Far-horizon terrain handling is thinner than PVsyst’s, which matters on hillside and alpine work, and the obstruction editor is less capable than PV*SOL’s on complex roofscapes. It is Windows desktop, so nothing runs from a phone on site, there is no satellite-derived 3D capture so every neighbouring volume is placed by hand, and there is no client-facing shading animation. It is the right tool for the Italian document and a middling one for the shading physics.

4. PV*SOL premium

What it does best. The animated 3D shading walkthrough is the best client-facing shading explanation on this list. Place the neighbouring palazzo, the torretta and the comignolo, then play the year and watch the shadow move across the array. In Italy that has a specific use beyond persuasion: when you are explaining why the permitted, heritage-approved position produces less than the position the client wanted, an animation showing the building’s own volume eating the courtyard pitch in January ends the argument faster than a table does.

Pricing. PVSOL premium is a subscription rather than a perpetual licence: EUR 845 per named user per year plus VAT, with standard PVSOL at EUR 585. Five named users are EUR 4,225 a year, comfortably less than five SurgePV seats. Licences bought before 19 November 2024 remain usable indefinitely, but maintenance renewals on them ended on 1 October 2024.

Who it suits. Design-led firms that win work in the meeting, and anyone regularly selling a compromised layout.

Honest limitations. Windows desktop only, no collaboration, no satellite roof capture so every obstruction is placed manually, and that manual placement is slow on a dense Italian block. No CEI 0-21 labelling, no Ritiro Dedicato modelling, no CER concept, and its financial module is built on German feed-in logic. Our PV*SOL alternative guide covers where a switch pays.

5. HelioScope

What it does best. Module-level 8,760-hour simulation for commercial roofs with a clean, exportable loss tree that Italian independent engineers and international funds accept without argument. On a 700 kW capannone roof in Emilia-Romagna its handling of mutual row shading is good and the report is fast.

Pricing. HelioScope prices in US dollars: Basic US$159 a month, US$1,620 a year, and Pro US$259 a month, US$2,640 a year, each covering one user and ten projects a month, with DC design capped at 1.25 MW on Basic and 5 MW on Pro. At €0.91 per dollar that is about €145 and €236 a month. Five Basic seats are US$8,100 a year.

Who it suits. Consultancies and C&I-only teams whose deliverable is a yield report.

Honest limitations. No Italian regulatory layer, no CEI labelling, no GSE modelling, no CER logic. Obstruction modelling on the complex pitched geometry of Italian housing is coarser than PV*SOL, and terrain slope handling is weaker than PVsyst. Read our HelioScope alternative guide before committing five seats.

6. Scanifly

What it does best. Scanifly turns a drone flight into a photogrammetric 3D model of the real site, then runs shading against measured geometry rather than an operator’s guess. Italy is close to the ideal case for this. In a centro storico the obstruction that decides the yield is a neighbouring facade whose height, overhang and roofline nobody can estimate accurately from the street or from a satellite image looking straight down. A point cloud removes the guess.

Pricing. Scanifly does not publish pricing. There is no vendor price list, no per-project rate and no per-seat rate on its site, so the only honest figure is a quote you obtain yourself. Any per-project or per-seat number circulating in software directories is unverified. See our Scanifly pricing breakdown for what is and is not knowable.

Who it suits. Firms already flying drones, and anyone whose shading disputes come down to a neighbouring building.

Honest limitations. You need a drone, a pilot and permission to fly, and in Italian historic centres and near protected sites that permission is a real constraint rather than a formality under ENAC and EU drone rules. It is a capture tool rather than a design suite or financial model, so it sits alongside your platform. Our Scanifly alternative piece covers the tradeoff.

7. Solmetric SunEye 210

What it does best. A handheld fisheye instrument that photographs the whole sky dome from one point on the roof and overlays the annual sun path, giving a measured horizon and a monthly solar access percentage for that exact spot. On a hillside site where the terrain horizon is the dominant loss, or on a heritage-constrained position where you are documenting why a compromised layout underperforms, a measurement taken on the roof is evidence in a way a simulation is not.

Pricing. US$2,195 for the base North American kit, bought new from Solmetric, which is about €2,000 at €0.91 per dollar. The price includes a lifetime PV Designer licence. It was out of stock as of 2 August 2026 with a stated 10 to 12 week lead time, so plan the purchase ahead of a project rather than during one.

Who it suits. Audit teams, expert witnesses, and designers documenting a constrained position for a client or a condominio.

Honest limitations. It is a current product rather than a discontinued one, and Solmetric has been a Fluke company since the acquisition announced on 12 September 2023, but stock is not immediate and the lead time can outrun a project programme. It measures one point, so a large or stepped roof needs several readings. It outputs solar access percentages rather than energy, so the result still has to be carried into a simulation engine.

8. PVGIS Horizon Import

What it does best. Not a design tool, an input. The European Commission’s Joint Research Centre publishes PVGIS free, including a terrain horizon profile for any Italian coordinate, which imports straight into PVsyst or PV*SOL. Given how much Italian PV sits in valleys, on hillsides and in the Appennini and alpine arc, this is not an optional refinement. In a narrow alpine valley the far horizon can remove the first and last hours of the winter day entirely, and no near-shading model will mention it.

Pricing. Free. Meteonorm sells a commercial equivalent with finer modelling and publishes its price: CHF 675 for a first licence and CHF 350 for each additional licence, excluding VAT, bought once per software version rather than as an annual subscription.

Who it suits. Anyone designing in a valley, a hill town, or under a ridge, which in Italy is a large share of all sites.

Honest limitations. Terrain horizon only. It knows nothing about the palazzo across the street or the comignolo on your own roof, which is where most Italian urban shading loss lives. It complements a near-shading engine rather than replacing one.

9. Polysun

What it does best. Vela Solaris built Polysun around coupled systems, so a shading loss lands in the same model as the heat pump, the storage and the hot water. With export now earning a wholesale-linked Ritiro Dedicato price rather than a Scambio sul Posto credit, self-consumption fraction is the number that decides Italian paybacks, and a coupled model shows how a shaded array moves it.

Pricing. Vela Solaris does not publish Polysun pricing. It sells either a one-off purchase plus an annual service subscription, or a lease with a twelve-month minimum, and quotes on request. A EUR 699 figure circulating in software directories traces back to a 2013 price list and should not be treated as current.

Who it suits. Studi doing renovation and sector-coupling work.

Honest limitations. Shading is a component of a larger simulation rather than the focus. The 3D obstruction editor is weaker than PV*SOL’s, terrain handling is limited, and there is no client-facing animation and no Italian document output. If you never touch heat, it is the wrong purchase.

10. Aurora Solar

What it does best. Strong residential shade rendering with mature roof plane detection and a polished customer-facing presentation, plus LIDAR-backed irradiance where coverage exists.

Pricing. Aurora publishes US dollar prices: Basic US$135 per user per month billed annually, US$159 monthly, and Premium US$220 billed annually, US$259 monthly, each covering one user and 50 projects a month. At €0.91 per dollar that is about €123 and €200. Five Premium seats come to US$13,200 a year and five Basic seats to US$8,100. The old Grow, Scale and Run tiers no longer exist. Worth stating plainly: Aurora Basic at US$1,620 a year undercuts a single SurgePV Individual seat at US$1,899.

Who it suits. Multinational installers extending an existing Aurora process into Italy.

Honest limitations. LIDAR modelling and bankable shade reports sit on Premium rather than Basic, which catches small firms mid-project, and plan sets are a separately priced service rather than a plan inclusion. LIDAR coverage is far better in North America than in Italy, and the Italian regulatory layer is essentially absent: no CEI labelling, no GSE modelling, no CER concept. Per-seat monthly pricing scales painfully. See our Aurora Solar alternative comparison.

Get your sizing sanity-checked. For a fast independent second opinion on system size and payback before you finalise a constrained layout, run the numbers through our free solar calculator or talk to our engineering team.

The Hillside and Heritage Shading Test: Six Checks

This is the framework we run on our own solar EPC work before a shaded Italian design leaves the office. It takes about fifteen minutes and it catches most of what a strutturista or a client’s engineer would find.

1. Correct the shadow multiple for slope before anything else. Add the slope angle to the winter solar elevation for a south-facing slope, subtract it for a north-facing one, then take one over the tangent. Near Rome that moves the multiple between 1.45x and 3.82x for a mere ten degree slope. If your software takes a flat ground plane, it is answering a different site’s question.
2. Import a PVGIS horizon profile for the coordinate. In a valley or under a ridge the terrain removes winter hours that no near-shading model will flag. Do this before you place a single obstruction.
3. Measure the neighbours, do not estimate them. In a centro storico the deciding obstruction is a facade across a narrow street. A building 4 m taller across a 4 m gap blocks everything below about 45 degrees from that direction. A three metre error in its height changes the winter answer completely. Fly it, or take a fisheye reading from the roof.
4. Run the permitted layout and the ideal layout as two full simulations. Not one simulation with an orientation factor applied. The orientation penalty and the shading penalty compound non-linearly at module level, and the client is entitled to the real difference in kWh, in self-consumption fraction and in payback years.
5. Export hourly, not annually, if a CER is involved. Shared energy is an hourly coincidence between member production and member consumption. An annual or monthly shading figure cannot feed that calculation honestly.
6. Check the sky model and the loss resolution. Perez or Hay-Davies, never isotropic, and bypass-diode physics rather than an area percentage. A roof with 8 percent geometric shade routinely loses 15 to 22 percent of annual energy once mismatch is counted.

Mistakes Italian Installers Make in Shading Analysis

1. 1
   Treating the ground as flat. A ten degree slope moves the achievable ground coverage ratio between 0.36 and 0.63 at Roman latitude depending on aspect. On a hill town or a terraced site, a flat-plane assumption is not a rounding error, it is the wrong design.
2. 2
   Using one national default down the whole peninsula. The winter shadow multiple runs from 1.85x in Palermo to 2.74x in Bolzano. A single spacing rule is too sparse in Sicily and too dense in Alto Adige, and neither error is cheap.
3. 3
   Accepting a heritage-constrained position without pricing it. The client is trading energy for permission. Show both layouts as full simulations with the difference in kWh, self-consumption fraction and payback, then offer a mitigation costed against that number.
4. 4
   Feeding a CER model an annual shading figure. Shared energy is an hourly overlap between member production and member consumption. Smooth the shading input and the shared-energy estimate the whole community business plan rests on is soft.
5. 5
   Telling a client the GSE requires a shading report. It does not. Ritiro Dedicato, the CER incentive and the connection process run on plant, meter and conformity data. Sell the study on accuracy and on the permitting trade it prices, not on an invented requirement.

The wider set of process failures is covered in our writeup on common mistakes EPC companies make in rooftop solar, and the full Italian software stack guide puts shading in the context of the other licences you will buy.

Where PVsyst, ACCA and PV*SOL Still Beat SurgePV

Verdict. For an Italian firm working hillside sites and constrained urban roofs at volume, SurgePV wins because terrain and neighbouring volumes come from satellite rather than from an operator’s hand, and because comparing a permitted layout against an ideal one is a two-minute job rather than a two-hour one. For a lender-reviewed yield report PVsyst stays, for a building file with a computo metrico ACCA stays, and for a client meeting where the compromise has to be explained PV*SOL still does it best. Two licences is a normal answer in Italy and we would say so on a sales call.

How Heaven Green Energy and SurgePV Help Italian Teams

Heaven Green Energy has delivered more than 10,000 solar installations, and our engineering group builds the software our own designers use. SurgePV came out of that, written by people who had to defend a yield number to a client who could see the neighbour’s roof from their own window. For Italian teams the entry points are:

• Shadow analysis for the 8,760-hour module-level simulation and the permitted-versus-ideal layout comparison.
• Structural and civil engineering for the NTC 2018 snow, wind and seismic check a hillside or alpine mounting decision triggers.
• Solar inverter sizing for the string and MPPT side of a shaded or split-orientation layout.

If you run projects beyond Italy, our commercial solar and industrial solar pages set out how the same design stack carries across markets. Wider context sits with the IEA renewables tracker, IRENA country profiles and Terna’s Italian electricity statistics.

Related Shading and Design Software Guides

• Solar Shading Analysis Software: The Global Guide
• Solar Shading Analysis Software in Spain
• Solar Shading Analysis Software in Germany
• Solar Shading Analysis Software in Poland
• Best Solar Design Software in Italy
• Best Solar Proposal Software in Italy
• Best Solar Software in Italy: The Full Stack
• Best Solar Design Software: The Global Ranking
• PV Yield Simulation Software Compared
• Commercial Solar Design Software Compared

Frequently Asked Questions

What is the best solar shading analysis software for Italy in 2026?

SurgePV ranks first, at about €1,180 per user per year on the 5-User Team plan, because it runs an 8,760-hour module-level shading simulation with bypass-diode physics, picks up terrain slope and neighbouring building volumes from satellite rather than assuming a flat plane, and lets you compare a heritage-permitted layout against the ideal one as two full simulations. PVsyst ranks second and remains the format an Italian bank’s technical adviser asks for by name. ACCA Solarius-PV ranks third on shading specifically.

Why does hillside slope change solar row spacing so much?

Because row spacing is set by the sun’s elevation relative to the ground plane, not the horizontal. A south-facing slope adds its angle to the effective elevation and a north-facing slope subtracts it. Near Rome, where December solar noon is 24.7 degrees, a modest 10 degree south slope gives an effective 34.7 degrees and a shadow multiple of 1.45x, while a 10 degree north slope gives 14.7 degrees and 3.82x. The achievable ground coverage ratio moves from about 0.63 to about 0.36 on the same latitude.

Is a shading report required for a GSE process in Italy?

No. Ritiro Dedicato, the CER incentive and the distributor connection process run on plant registration data, meter data, inverter conformity declarations and the CEI 0-21 or CEI 0-16 documentation. None of them defines a shading factor or asks for a shading study. The genuine regulatory constraint on Italian array placement is the heritage route instead: works in areas protected under the Codice dei beni culturali e del paesaggio need an autorizzazione paesaggistica, which is an appearance decision rather than an energy one.

How does a vincolo paesaggistico affect shading design?

It frequently moves the array onto the roof plane that is invisible from the street, which is often the courtyard, rear or below-ridge position, and that position is usually both worse oriented and more shaded by the building’s own volume or by neighbours. Those two penalties compound non-linearly, so adding an orientation factor to a shading factor understates the loss. The honest deliverable is two complete simulations, the unconstrained layout and the permitted one, compared in kWh, self-consumption fraction and payback.

How long is a winter shadow in Italy?

It depends heavily on where you are. Palermo at 38.1 degrees north gets a December solar noon elevation of 28.5 degrees, so shadows run 1.85 times object height. Rome at 41.9 degrees gets 24.7 degrees and 2.18 times. Milan at 45.5 degrees gets 21.1 degrees and 2.60 times. Bolzano at 46.5 degrees gets 20.1 degrees and 2.74 times. Berlin, for contrast, gets 14.1 degrees and 3.99 times, which is why German-derived spacing defaults waste Italian roof area.

How does shading affect a Comunità Energetica Rinnovabile?

The CER incentive is paid on shared energy, the hourly overlap between what members produce and what members consume inside the same primary substation area. So a shading loss in an hour when member consumption already exceeds production reduces shared energy directly, while a loss in an hour of community surplus may cost almost nothing because that energy was only earning a Ritiro Dedicato price. Judging which is which needs hourly shaded production per site, not an annual percentage.

Is ACCA Solarius-PV good enough for shading analysis?

For a studio whose deliverable is the Italian document set, usually yes. Its 3D shading model is competent and it is wired straight into the relazione tecnica, schema elettrico and computo metrico, which removes transcription errors and saves real time. On shading depth specifically it is behind PVsyst on far-horizon terrain handling and behind PV*SOL on complex obstruction editing, and it has no satellite-derived 3D capture, so every neighbouring volume is placed by hand. That is why it ranks second on our Italian design page and third here.

What is SurgePV’s biggest weakness for Italian shading work?

Satellite-derived geometry is weakest exactly where Italy is hardest, which is a narrow street with tall facades and overhangs that an overhead image resolves poorly, and SurgePV has no drone photogrammetry ingest and cannot import a measured fisheye horizon file to correct it. It also does no portfolio-level CER shared-energy optimisation, so community arithmetic stays in a separate model, and it produces no computo metrico estimativo priced against a regional prezzario, which keeps ACCA in most Italian studi regardless.