Commercial Solar Installation Costs NSW 2026 - Get Free Quotes

Commercial Solar Costs in NSW

A 10kW system installed runs $8,000 to $14,000, a 30kW system $22,000 to $38,000, and a 50kW system $35,000 to $60,000. At 100kW expect $70,000 to $120,000, and a 250kW array across a warehouse roof lands between $175,000 and $300,000. Those figures are after small-scale certificates have been applied where the system qualifies for them. General installation is covered at commercial solar installation, with residential comparison at residential solar installation. Anything larger than 250kW becomes a construction project with its own procurement process attached.

Per watt is the measure the industry actually uses and it is worth understanding. Most commercial systems in New South Wales price between $0.70 and $1.20 per watt installed, with the rate falling as the system grows because the fixed costs of design, approval and mobilisation spread across more capacity. A 10kW system carries the same paperwork as a 30kW one. That is why small commercial arrays look expensive against the residential figures people have heard. Compare rates within a size band and not across them. A 15kW quote and a 60kW quote should never be judged on the same per watt figure.

Several costs sit outside the per watt rate and they are the ones that vary most between quotes. A switchboard upgrade runs $3,000 to $15,000, structural engineering $1,500 to $5,000, a network connection application anywhere from a few hundred to several thousand, and tilt frames add $50 to $150 per panel on a flat roof. None of those is optional where the site requires them. Work out which of those sit inside the figure you have been given. Two quotes on the same roof can differ by twenty thousand dollars on exclusions alone.

What You Pay For

Panels are the visible cost and the smallest lever on the total. Tier one manufacturers such as Jinko, Trina, LONGi, REC and Q Cells all produce reliable product at broadly similar output, and the difference between the cheapest and dearest panel on a 50kW system is modest against the whole project. Panel choice matters more for the warranty position and the manufacturer's likely longevity than for the electricity produced. Approved products are listed by the Clean Energy Council and an installer should be working from that list. Panel degradation rates differ slightly and are stated in the performance warranty. Over twenty five years that difference is measurable but modest against the other variables.

Inverters are where a commercial system succeeds or fails over twenty years. String inverters from Fronius, SMA, Sungrow and Huawei dominate the commercial market, and the choice affects monitoring, servicing and how the system behaves when one string underperforms. An inverter is also the component most likely to need replacement during the system life, so local support and parts availability matter more than the specification sheet. Inverter work is covered at solar inverter installation and replacement.

Mounting and racking is a bigger line on commercial roofs than most people expect. A tilted metal roof takes a straightforward rail system, while a flat membrane roof needs ballasted or penetrating frames engineered for wind uplift, and that changes both the material and the labour. Tilt frames on a flat roof also space the rows apart to avoid shading, which reduces how much capacity a given roof area will hold. Establish what mounting system is proposed and whether the roof type has been confirmed on site. Ballasted systems avoid roof penetrations entirely but add considerable weight, which is exactly why the structural assessment has to come before the mounting decision is made. Row spacing on a flat roof also reduces how much capacity a given area will hold.

Electrical work between the array and the switchboard is real money on a large site. Cable runs across a warehouse, isolators, protection devices and the connection into the main switchboard all scale with the distance involved, and a switchboard at the far end of a building costs considerably more to reach than one below the array. Commercial electrical work is covered at commercial electrical maintenance. Find out where the switchboard sits relative to the roof space before accepting any figure. Voltage drop over a long run pushes the cable size up and the cost with it.

Access equipment is a genuine cost that residential quotes never carry. Scissor lifts, boom lifts, edge protection and roof anchor points all appear on commercial jobs, and a two storey factory with no permanent roof access needs equipment hired for the duration. Height safety obligations sit with SafeWork NSW and are not negotiable on a commercial site. An installer who has not visited the roof cannot have priced this properly. Documented safe work method statements are part of the job on any commercial roof. A crew turning up without them is a liability and not a saving.

Monitoring is worth paying for on a commercial system and it is frequently cut to sharpen a quote. Per string or per panel monitoring shows you which part of an array is underperforming instead of telling you the total is lower than expected, and on a large system that difference is the difference between a fixed fault and a slow decline nobody notices. Optimisation is handled under solar monitoring and optimisation. Expect $500 to $3,000 depending on how granular the reporting is, and treat it as part of the system and not an accessory to it.

Cost by System Size

A 10kW to 20kW system suits a small shopfront, a medical practice or an office tenancy. At $8,000 to $26,000 installed it is priced closer to the residential market than the commercial one, and it usually connects to an existing three phase supply without major switchboard work. Comparison pricing appears at 10kW solar system costs. The economics work best where the business operates through daylight hours and consumes nearly everything it generates. Three phase supply is close to universal on commercial premises and simplifies the connection. Most tenancies of that size are already on a supply capable of carrying the inverter.

The 30kW to 50kW band is the most common commercial installation in New South Wales. It suits a light industrial unit, a childcare centre, a small manufacturer or a medium sized retail site, and at $22,000 to $60,000 it typically pays back inside four to six years on a daytime load. This is also the band where the per watt rate improves noticeably over the smaller systems. Most installers quoting commercial work are comfortable in this range.

Systems from 50kW to 100kW need more careful network engagement and more careful design. The connection process becomes more involved, export limiting is common, and the switchboard and cabling work grows accordingly. At $35,000 to $120,000 the project starts to warrant proper financial modelling instead of a rule of thumb payback. Financing options are covered at solar financing. Export limiting is common enough in this band to plan for instead of hoping against.

Above 100kW the project changes character entirely. The incentive structure moves from upfront certificates to annual ones, network approval becomes a formal process with engineering studies, and installation moves into commercial construction territory with programme, site inductions and staged commissioning. At $175,000 to $300,000 for 250kW the per watt rate is at its best. The cost is time instead, since these projects run months instead of weeks. Staged commissioning means the system comes online in sections instead of all at once. Expect months instead of weeks from the first conversation to full output.

Batteries change the arithmetic and are worth considering separately instead of assuming. Storage lets a business use generation outside daylight hours and can reduce demand charges where the tariff includes them, but it adds substantially to the capital cost and the payback is more sensitive to the tariff structure. Storage is priced at solar battery storage installation. Model the solar case and the solar plus storage case as two separate decisions.

Carport mounted solar is the option for businesses with parking and no usable roof. A solar carport costs considerably more per watt than a roof mount because the structure itself has to be built, engineered and footed, but it produces shaded parking and a mounting surface at the same time. Structures of this kind are covered at solar carport installation. It also pairs naturally with vehicle charging, which is covered at commercial EV charging station installation. A carport also has a planning pathway that a rooftop array often does not. Confirm the approval position before designing the structure.

STCs, LGCs and What They Pay

Small-scale technology certificates are the reason quoted prices look lower than the equipment would suggest. Systems up to 100kW create STCs based on the expected generation over a deeming period, and installers almost always assign those certificates against the price so the figure you see is already net of them. The scheme is administered by the Clean Energy Regulator. You are not applying for anything, but you are entitled to know what value has been assigned. The value assigned should be shown as a line on the quote.

The deeming period shrinks every year and that matters to timing. Certificates are calculated on the years remaining until the scheme concludes at the end of 2030, so the same system installed a year later creates fewer certificates and carries a higher net price. That is a genuine reason to move sooner and not a sales tactic. Confirm the current deeming multiplier with the regulator instead of accepting an installer's characterisation of it. Nothing about the deeming reduction is discretionary, since it is set in the scheme itself.

Certificate value fluctuates because STCs are traded. The price moves with market supply and demand, which means a quote given six weeks ago may no longer reflect the value being assigned. Have the STC value and the assumed price to be stated separately on the quote instead of buried in a single net figure. That way you can see what changes if the market moves before installation. A quote with a stated certificate value and price is one you can check independently. Certificate prices move weekly and a stale quote reflects a stale assumption.

Above 100kW the system moves to large-scale generation certificates and the cash flow inverts completely. LGCs are created annually based on actual generation instead of upfront on expected generation, so instead of a discount at purchase you receive a revenue stream over the system life. That means a higher upfront cost and an ongoing income, and it requires accreditation as a power station and annual reporting. Businesses crossing that threshold should take advice on whether the administrative load suits them. The threshold is measured on system capacity instead of annual generation, so confirming exactly how your proposed system is measured against it is worth doing explicitly with the installer.

Sizing decisions cluster around the 100kW line for exactly this reason. A business that could justify 110kW will sometimes install 99kW instead, taking the upfront certificate benefit and avoiding the ongoing compliance. Whether that is the right call depends on the load, the roof and how the business values cash now against income later. It is a question for your accountant as much as your installer.

Tax treatment is worth raising with your adviser early. Commercial solar is a capital asset and the depreciation treatment, along with any write-off provisions in force at the time, materially affects the after tax cost of the project. Those provisions change with each budget cycle, so nothing written on a webpage should be relied on. State energy programmes may also be available and are published through Energy NSW. Get the tax position confirmed before you commit and not at the end of the financial year. Nothing about the tax position should come from an installer's sales material.

Grid Connection and Exports

Your network operator has to approve the connection before anything is switched on. In New South Wales that is Ausgrid across Sydney, the Central Coast and the Hunter, Endeavour Energy through Sydney's west and south and the Illawarra, and Essential Energy across regional areas. Each has its own application process, its own timeframes and its own view of what a given part of the network can accept. The installer usually lodges the application, but it is your connection and the outcome is yours to live with. Approval timeframes vary considerably between the three operators, so find out which network your site sits on before you start building a programme around it.

Approval is not automatic and this is where commercial projects most often stall. A network with existing constraint in the area may limit what you can export, require a study before deciding, or approve the system on the condition that it exports nothing at all. That decision arrives after design and before installation, which is why a project timeline should include it explicitly. Put it to each installer: what do they expect the network to say and how long the application usually takes in your area. A study on a constrained part of the network can add weeks to the programme. A constrained feeder can turn a straightforward project into a months long conversation.

Zero export and export limiting are common outcomes on commercial systems and they are not disasters. A zero export system generates for your own consumption and simply cannot push anything back to the grid, which for a business consuming most of its generation on site changes very little. The control is achieved with metering and inverter settings that reduce output when export would occur. Where a system is heavily export limited, the design should be sized to consumption from the outset.

Feed-in tariffs are the reason exports matter less than people assume. A business pays a retail rate for electricity from the grid and receives a much smaller rate for electricity sent back, so every kilowatt hour consumed on site is worth several times one exported. Current tariff information is covered at solar feed-in tariffs. That single asymmetry between the import rate and the export rate is what should be driving the system size, and it is the reason a roof full of panels is not automatically the right answer.

Metering has to change and it is a separate arrangement from the connection approval. A bidirectional meter capable of recording import and export is required, and that is organised through your electricity retailer instead of your installer or the network. Retailers vary considerably in how quickly they attend. A system sitting commissioned but unable to operate while a meter change is scheduled is a common and avoidable frustration. Ask your retailer about the meter change at the same time you sign the contract. The retailer, the network and the installer are three separate parties on this step.

Demand charges deserve attention because solar affects them less than businesses expect. Many commercial tariffs charge for peak demand measured in kilovolt amperes as well as for energy consumed, and solar reduces the energy component reliably while doing much less for a demand peak that occurs on a cloudy afternoon or after dark. A business with a high demand charge may find the savings smaller than a simple kilowatt hour calculation suggests. Look at a full year of bills and identify which component the money actually goes to. Businesses on a flat rate tariff have a simpler calculation and usually a better one.

Sizing to Your Consumption

The single most useful input to a commercial solar design is twelve months of interval data. Your retailer can provide it, it shows consumption in half hour or fifteen minute blocks, and it reveals the shape of your load in a way a monthly bill never will. An installer designing from an annual kilowatt hour total is estimating, and an installer designing from interval data is engineering. Most retailers provide it on request at no cost, so request it before you approach anybody for a quote.

Load shape decides the outcome more than roof area does. A bakery drawing heavily from three in the morning, a cold store running overnight and an office consuming from eight to six are three entirely different solar propositions on identical buildings. The daytime consumers do well and the overnight consumers do not, at least without storage. Be honest about which one your business is before you fall in love with a roof full of panels. Storage changes the picture for overnight consumers, though not cheaply, so model both cases before deciding which of those businesses you actually are.

Self consumption is the metric that matters and it should appear in every proposal. It expresses what proportion of the generation your business uses on site instead of exporting, and a well designed commercial system usually targets a high figure. An installer who cannot tell you the modelled self consumption has not modelled it. Request the number along with the assumptions that produced it.

Seasonal variation catches businesses that only look at an annual figure. A site with heavy summer air conditioning load matches solar generation beautifully, while a business whose demand peaks in winter does not, and the same system produces a different result in each case. Air conditioning load is covered at commercial air conditioning. Request the modelling month by month instead of as a single annual saving. Weekend operation matters too, since a site closed on Saturday and Sunday exports for two days in seven.

Future load is worth building into the design where it is genuinely coming. Adding electric vehicle charging, electrifying a gas process or expanding production all increase daytime consumption and improve the case for a larger system. Load management for charging is covered at EV charger load management. What is not worth doing is oversizing on a vague intention, since a system generating power nobody uses earns the export rate and nothing more. A signed contract for new plant is a firm intention, and a board discussion is not.

Roof area sets the ceiling and it is usually less than the plan suggests. Skylights, air conditioning plant, exhaust fans, walkways, fire service access and required setbacks from roof edges all remove usable area, and on a flat roof the row spacing needed to avoid self shading reduces it further again. A rule of thumb of six to eight square metres per kilowatt is a starting point on a tilted roof and more on a flat one. A physical roof inspection is what turns that estimate into a number, and a drone survey is a reasonable substitute where roof access is difficult.

Roof, Structure and Asbestos

Structural capacity has to be established before panels go on and it is not a formality. An array adds distributed load and, more importantly, wind uplift, and older industrial buildings were not designed with either in mind. A structural engineer's assessment costs $1,500 to $5,000 and is money well spent on any building of unknown provenance. Where a building certifier or an insurer asks later, that report is what answers them.

Wind loading is the part that surprises people. Panels present a surface to the wind and the fixings have to resist uplift calculated for the region, the terrain and the height of the building, which is why a coastal warehouse needs more substantial mounting than an inland one of the same size. Structural design standards are published by Standards Australia and referenced by the building code. An installer proposing the same fixing pattern on every job has not done this calculation. Coastal sites in particular need fixings rated for the exposure.

Roof condition decides whether the timing is right at all. A metal roof with ten years of life left is a reasonable host for a twenty five year array, and one with rust at the laps is not, because removing and reinstating an array to replace a roof is an expensive exercise. Roofing work is covered at roofing services. Have the roof assessed honestly before committing, since the cheapest time to replace it is before the panels go on.

Asbestos cement roof sheeting is a serious consideration across older New South Wales industrial areas. A great many factories and warehouses built before 1990 across western Sydney, Newcastle and the regional centres have asbestos cement roofing, and drilling or fixing into it is not permitted. Removal is licensed work covered at asbestos roof removal, with identification at asbestos testing and inspection. Establish the roof material before an installer quotes, because it can change the project from an installation into a roof replacement. A roof replacement combined with a solar installation is a single project worth pricing as one.

Penetrations and warranty are worth settling in writing. Every roof fixing is a potential leak point, and where a roof carries a manufacturer or installer warranty, penetrating it can void that cover unless the work is done to their specification. Non penetrating ballasted systems avoid the issue on flat roofs at the cost of additional weight. Ask who carries responsibility for a leak that appears at a mounting point two years later.

Leased premises need the landlord involved before design begins. A tenant installing solar on a building they do not own faces questions about consent, who owns the asset at the end of the lease, what happens on assignment and whether make good obligations require removal. None of that is difficult, but all of it is slow if it starts late. Raise it with the landlord at the same time you start collecting quotes, since some will fund the system themselves and adjust the rent instead.

Accreditation and Standards

Accredited installation is what makes a system eligible for certificates. Installers and designers working on systems that claim small-scale certificates must hold current accreditation, which is now administered by Solar Accreditation Australia after the scheme transferred from the Clean Energy Council. An unaccredited installation cannot create certificates, which turns a discounted price into the full price. Request the accreditation number and check it.

Electrical licensing is separate and equally necessary. The connection work is licensed electrical work in New South Wales and must be performed by a licensed electrician, with certification issued on completion. Licensed electricians appear on the public register kept by NSW Fair Trading. Broader electrical work is covered at electrical services.

A large system often needs work at switchboard upgrade level as well, and on an older commercial board that is a cost worth establishing before the solar quote is accepted rather than after. Certification for the electrical work should be provided on completion as a matter of course, since it is what an insurer will ask for after any incident. Keep it with the system documentation rather than the invoice folder.

The technical standards behind the installation are worth naming because quotes reference them. Photovoltaic array installation, inverter grid connection requirements and the general wiring rules are all published through Standards Australia and called up by the regulatory framework. They govern isolation, labelling, cable protection and how an inverter must behave when the grid goes down. A quote citing the correct standards is a reasonable sign of an installer who works to them. Labelling and isolation requirements exist so an electrician can safely work on the array later.

Planning approval applies to some commercial installations and not others. Roof mounted solar on many commercial buildings falls within exempt development, while heritage listed buildings, some conservation areas and ground mounted arrays can require a development application. Planning pathways are administered through Planning NSW and applied by your council. Confirm the pathway before design is finalised, since it affects the timeline more than the cost. A council planning enquiry costs nothing and settles the question early.

Warranties on a commercial system come in three separate layers and they are frequently conflated. Panels carry a product warranty and a longer performance warranty, inverters carry their own much shorter product warranty, and the installer carries a workmanship warranty on the installation itself. Each is only as good as the entity behind it. Establish what happens to the workmanship warranty if the installer ceases trading, since that is the layer most likely to disappear.

Maintenance is modest but it is not nothing on a commercial array. Panels lose output as dust and grime accumulate, particularly on a low tilt roof near a road or an industrial process, and inverters need periodic inspection. Cleaning is covered at solar panel cleaning, with faults at solar panel repairs and maintenance.

A cleaning interval of once or twice a year suits most metropolitan sites, moving to quarterly where a nearby industrial process or an unsealed road puts a real load of dust on the array. Consumer guarantees on both the equipment and the work are administered by the ACCC. Monitoring output against the same period last year is the cheapest way to know whether a clean is due.

What Drives the Price

System size is the primary driver and the rate improves as it grows. Fixed costs of design, network application, mobilisation and commissioning spread across more capacity, which is why a 100kW system costs far less than ten times a 10kW one. That effect is strongest between 10kW and 50kW, and beyond 100kW the per watt rate flattens out while site factors take over as the main variable. Compare rates within a size band and never across two of them.

Roof type changes the mounting cost substantially. A tilted metal roof with good access takes a straightforward rail system, while a flat membrane roof needs engineered ballast or penetrating frames, and a tiled roof on a commercial building is slower again. Each of those is a different labour figure for the same array. Tell every installer what the roof is made of and what pitch it sits at.

Switchboard condition is the most common unbudgeted cost on commercial solar. An older board with no spare capacity, no room for the required protection devices or asbestos backing panels needs upgrading before a system can connect, and that is $3,000 to $15,000 on its own. An installer who has not opened the board has not priced it. Comparison figures appear at switchboard upgrade costs, and asbestos backing panels in an older board are a common and unwelcome discovery.

Cable run distance scales quietly and can be significant. A switchboard directly below the array is inexpensive to reach, while a board at the opposite end of a large warehouse means long cable runs in proper containment, and both the copper and the labour add up. On very long runs the cable size increases to manage voltage drop, which increases the cost again. Establish where the connection point is and how far the cable has to travel. Containment on an exposed run is a cost in its own right.

Access and height requirements affect the labour on every commercial job. A single storey factory with permanent roof access is straightforward, while a multi storey building or a site with no anchor points needs hired equipment, edge protection and a documented safe work method. Those costs are real and they belong in the quote instead of appearing later. An installer who has not been to the site cannot have included them accurately.

Sydney Metro Costs

Sydney has the largest concentration of commercial solar installers in the state and competition at the 30kW to 100kW end is genuine. Roof material and switchboard condition account for most of the price difference between two sites, far more than the postcode. A 2018 industrial unit in a business park and a 1975 factory in an older industrial area are different projects with the same roof area. Neither is reliably dearer until somebody has been on the roof, and getting three quotes in this band is both realistic and worth the effort.

The older industrial areas carry the asbestos question most heavily. Parts of western Sydney, the inner south and the older Parramatta corridor have significant stock of pre 1990 factories with asbestos cement roofing, and that single fact can change a solar project into a roof replacement project. Installers working those areas ask about it as a matter of routine. Establishing the roof material yourself before you request quotes saves everybody a round of revisions, and it costs nothing beyond a phone call to whoever maintains the building.

Newer business parks in the north west and south west are the easiest commercial solar sites in the state. Modern metal roofs at a good pitch, switchboards with spare capacity and clear roof access all reduce the unknowns, and quotes for those buildings tend to cluster closely. What can still catch a tenant out is the landlord consent process on a leased unit. Start that conversation early, because it moves at the landlord's pace and not yours. Ask the landlord early, since the process moves at their pace and not yours.

Network constraint varies by area and is not something you can assess from the street. Some parts of the Sydney network have limited capacity to accept additional export, which produces export limits or zero export conditions on approval. An installer who works regularly in your area will have a sense of what the network has been approving. Treat that as informed expectation instead of a guarantee, and ask what the network has been approving nearby in recent months.

Regional NSW Costs

Regional per watt rates sit slightly above metropolitan ones and travel is the main reason. Fewer installers cover much larger areas, crews stay overnight on multi day jobs, and equipment hire has to travel with them. Against that, regional sites frequently have larger roofs, better access and fewer shading obstructions. Ask whether travel and accommodation sit inside the quoted figure.

Network constraint is a bigger issue outside the metropolitan network than within it. Long rural feeders with limited capacity mean export limiting is common and zero export conditions are not unusual, particularly where other generation has already connected in the area. That is a design input and not an obstacle, provided it is known before the system is sized. Ask the installer to confirm the likely position with the network before the design is finalised. Long feeders are the reason regional constraint is more common than metropolitan constraint.

Agricultural businesses often have excellent solar cases and unusual load shapes. Irrigation pumping, cool rooms, dairies and processing sheds all draw heavily and many of them draw during daylight, which is exactly what suits solar. Shed and outbuilding electrical work is covered at shed electrical installation. Where the load is spread across several buildings on one property, the metering arrangement needs establishing early. Metering across several buildings on one title needs settling before design begins.

Dust and soiling reduce output more in agricultural and industrial settings than in a suburb. An array near an unsealed road, a quarry or a grain handling operation accumulates material that a suburban roof never sees, and output falls accordingly between cleans. Building a realistic cleaning interval into the operating cost is sensible instead of pessimistic. It is a modest annual figure against the generation it protects, and soiling losses are measurable enough to monitor instead of guessing at.

Service response is the practical constraint outside the cities. An inverter fault on a system three hours from the nearest technician means production lost while attendance is arranged, and on a large array that is real money. Find out who attends a fault, where they are based and what the response commitment is. A slightly dearer installer with local presence is frequently the better commercial decision. Local presence is worth paying a small premium for on a large array.

What to Look Out For

Insist on modelling against your own interval data. A proposal built on an annual consumption figure cannot tell you how much of the generation you will actually use, and self consumption is what determines the return. Any installer worth engaging will ask for the data before quoting. A quote arriving without it has assumed a load shape that may not be yours. A proposal without self consumption modelling is incomplete regardless of the price. A design premised on full export that returns export limited is a different investment.

Check what is excluded before you compare per watt rates. Switchboard upgrades, structural engineering, network application fees, access equipment and meter changes are all commonly left out of the headline figure, and a cheaper quote is frequently a less complete one. Ask each installer to list their exclusions explicitly, because the gap between two quotes almost always lives in that list. A cheaper number with four items missing from it is the dearer proposal once the site is understood.

Confirm the accreditation and the electrical licence separately. Accreditation is what makes the system eligible for certificates, the electrical licence is what makes the connection lawful, and they are different credentials held under different schemes. Both numbers should appear on the quote. A business that supplies neither without being asked is not one to hand a six figure project. Both credentials are verifiable in a few minutes online. Verification takes a few minutes and is worth doing on any project of this value.

Get the network position in writing before you sign. Whether the system can export, and how much, is decided by the network operator and not by the installer, and a design premised on full export that comes back export limited is a different investment. Ask what happens to the contract if the network imposes a limit, and read that clause closely before signing anything. A contract silent on the point leaves the entire risk sitting with you.

Treat any commercial proposal produced without a site visit with suspicion. Roof material, roof condition, structural capacity, switchboard state, cable route and access all change the figure materially, and none is visible from an aerial image. A quote produced from satellite imagery alone has assumed the best case on six separate unknowns. Expect a proper installer to want an hour on site before quoting, because that hour is what separates a proposal from a price.

What to Look for in a Quote in NSW

A commercial solar quote should state the system size in kilowatts, name the panels and inverter by make and model, and give the price per watt alongside the total. It should show the assigned certificate value separately from the net price, list exclusions explicitly, confirm who lodges the network application, and state whether structural certification and switchboard work are included. The modelled annual generation and self consumption belong on the document with the assumptions that produced them. The exclusions list and the network position are the two items that most often separate a cheap quote from a complete one. Anything the quote leaves blank is worth a call before you accept it.

Give every installer the same information. Twelve months of interval data, the roof material and pitch, the switchboard location and age, the building's age, whether the premises are leased and any planned change to the load all shape the design. Proposals built on different assumptions are not comparable in any meaningful way. Send the same data pack to each of them and note the same constraints. Interval data is the single most valuable thing you can send them. Interval data is the single most valuable thing you can hand an installer.

The questions asked before a number appears tell you a great deal. Somebody asking for interval data, asking what the roof is made of and when the switchboard was last worked on, and asking about lease arrangements is designing a system. A price quoted from a roof area and a postcode has sold you a product. That difference shows up in the generation figures years later instead of at the point of comparison. The reasoning behind the number matters more than the number itself.

Settle the data, the exclusions, the network position and the accreditation before you engage anybody. Confirm the modelling uses your interval data, get the exclusions in writing, establish what happens if export is limited, and check both credentials. Related work is grouped under solar panel installation, with larger fitouts at commercial builders. Sorting all four before signing costs a phone call, and sorting them afterwards costs a crane. Everything on a commercial solar quote follows from the load, the roof and the network. Get those four right and the rest of a solar proposal takes care of itself.