A 75kW commercial solar system can be a practical fit for a business with a substantial daytime electricity demand and a large, usable roof. Warehouses, factories, farms, food businesses and larger retail or leisure sites may be able to use a significant share of the electricity while it is being generated.
The panel count and roof space are not fixed by the system size alone. They depend on the wattage and dimensions of the chosen modules, the roof layout, access routes, shading and the electrical design. This guide explains how to make a useful first estimate for an Irish site. The figures are planning estimates, not a design specification or quotation.
In the calculations below, “75kW” means approximately 75kWp of solar-panel capacity: the panels’ combined rated output under standard test conditions. The inverter’s AC rating and the amount of electricity that can be exported are separate design choices.
What is a 75kW commercial solar system, and how does it work?
A photovoltaic (PV) system converts daylight into direct-current (DC) electricity. An inverter converts that electricity into alternating current (AC) for the building’s electrical system. Solar generation normally supplies on-site demand first; surplus may be exported if the grid connection and export arrangements allow it.
The difference between kW or kWp and kWh matters. Kilowatts (kW) describe power at a moment in time. Kilowatts-peak (kWp) describe the panels’ rated DC capacity under standard test conditions. Kilowatt-hours (kWh) measure electricity generated or consumed over time. A 75kWp array does not generate 75kWh every hour: its output changes with daylight, season, weather, orientation and system losses.
A commercial design may also include monitoring, isolation and protection equipment, and—where the load profile and business case support it—battery storage. Battery storage is optional; it is not required for a grid-connected solar PV system.
Which businesses can benefit from a 75kW solar installation?
This size may suit a business that can use much of its solar electricity during the working day. Potential candidates include:
•Warehouses and distribution centres with broad roof areas and daytime operations.
•Factories, workshops and food processors with steady machinery or refrigeration loads.
•Farms with suitable sheds and regular electricity use for milking, cooling, ventilation or processing.
•Hotels, leisure facilities and larger retail premises with daytime heating, cooling or equipment demand.
A large roof is not, by itself, a reason to install 75kWp. The best system size is usually matched to the building’s half-hourly electricity demand, available roof and connection capacity. Businesses that operate mainly at night may need a different configuration or a carefully assessed storage option.
How many panels are needed for a 75kW commercial solar system?
Use this simple calculation:
Number of panels = required system capacity in watts ÷ individual panel wattage
For a 75kWp panel array, that is 75,000 watts divided by the wattage of one module. Since a fraction of a panel cannot be installed, round up to a whole number. The resulting DC capacity may be slightly higher than 75kWp.
With 400W panels, the calculation is 75,000 ÷ 400 = 187.5, so the system would need 188 panels, giving a total capacity of 75.2kWp. With 450W panels, 75,000 ÷ 450 = 166.67, which rounds up to 167 panels and 75.15kWp. With 500W panels, 75,000 ÷ 500 = 150, so 150 panels provide exactly 75kWp. With 550W panels, 75,000 ÷ 550 = 136.36, so 137 panels provide 75.35kWp.
These are arithmetic examples, not a recommendation for a particular module. The final 75kW commercial solar panel system will use the modules available to the installer and a design that fits the roof, electrical equipment and grid connection. A designer may choose a different DC-to-AC ratio, so the panel nameplate total and inverter rating will not necessarily be identical.
Roof space requirements for a 75kW installation
Panel surface area versus usable roof area
Panel dimensions vary by manufacturer and model. For a preliminary estimate, commercial modules in the 400–550W range may occupy roughly 1.9–2.6m² each. Using representative dimensions for each of the panel-count examples above gives a combined panel surface area of approximately 330–370m². This is an estimate: the product datasheet should be used for an actual design.
That figure is only the panels’ footprint. A safe commercial layout also needs allowance for roof access, fire-safety provisions, maintenance routes, rooflights, vents, drains, plant equipment, edge setbacks and shading. Those constraints mean the gross roof area needed is larger than the combined panel area, and parts of a large roof may not be usable.
As an early planning allowance—not a guaranteed specification—set aside around 450–650m² of clear, usable roof for a compact, well-planned layout. A tilted arrangement on a flat roof can need more room to limit row-to-row shading and comply with site-specific wind, access and fire-safety requirements; roughly 550–800m² or more may be needed in some cases. The actual figure can fall outside these ranges once the roof and equipment layout are surveyed.
For comparison, SEAI gives a worked example in which a 30kWp array typically uses 75 panels and has an overall area of 125m². That example illustrates why the area depends on the selected module and the scheme’s definition of area; it should not be scaled mechanically to specify a 75kWp roof layout.[1]
Roof types and design factors
Metal roofs can be suitable where the cladding, purlins and fixings are in sound condition. The mounting method must be compatible with the roof profile and avoid compromising weather-tightness.
Flat roofs can accommodate flexible layouts, but mounting frames, ballast or roof penetrations must be designed for the roof structure and wind conditions. Tilted rows can require wider spacing and reduce the number of panels that fit.
Pitched roofs may provide useful unshaded areas, particularly where the roof faces south, east or west. The available planes, pitch, roof condition and safe access all influence the layout.
Across all roof types, the designer should assess orientation, tilt, shading from trees or nearby structures, cable routes and structural capacity. A structural roof assessment is especially important for older buildings, roofs near the end of their service life, or systems that add material loads. A professional site survey checks these constraints before the panel count and quote are finalised.
Estimated 75kW commercial solar system cost in Ireland
As a broad indicative, pre-grant guide, an Irish commercial solar pricing guide published in 2026 reports installed prices of roughly €900–€1,500 per kWp. Applied to 75kWp, that suggests an order-of-magnitude budget of about €67,500–€112,500.[4] Treat this as a starting range only. It is not a LVP Renewables quotation, and a site-specific proposal may be outside it.
The main items that can move the price include:
•Panel technology, module dimensions and product warranties.
•Inverter selection, monitoring and any battery storage.
•Roof type and mounting equipment, including any reinforcement or remedial work.
•Labour, safe access, scaffolding or lifting equipment.
•Cable distances, switchgear and electrical upgrades.
•Export limits, connection studies and any network works required.
•Site complexity, working hours and the amount of design or commissioning work.
A detailed quotation should state what is included and identify assumptions about roof condition, grid connection, VAT and any optional equipment. For an initial view of LVP’s photovoltaic services, see its page on PV panels and commercial solutions.
SEAI grants and financial support for commercial solar
As of 14 October 2026, SEAI’s Non-Domestic Microgen Grant page says support is available for eligible businesses and other listed organisations, with solar PV systems up to 1,000kWp covered by the scheme. It also states that an enhanced grant window runs from 6 October 2026 to 6 July 2027 for new applications, with grant support at an effective 45% rate.[1]
Under the grant table published on that page, the 21–200kWp band is listed at €400 per kWp. On that basis, a 75kWp system points to a grant figure of up to €30,000 before the scheme’s invoice-cost limit and other terms are applied. SEAI says the final payment is the lower of the value on the application summary and 45% of the invoiced cost. The published terms, application date, eligible costs and conditions should be checked with SEAI before a project is committed. Do not begin the works before receiving the grant offer; the scheme requires a registered Non-Domestic Microgen company and an application to ESB Networks before installation.[1]
Grant rates, eligibility and application windows can change. A grant is not guaranteed until an eligible applicant has an offer and meets the scheme requirements. Businesses should also ask their accountant or financial adviser to check any other applicable tax treatment or funding route rather than assuming supports can be combined.
Expected annual electricity generation in Ireland
An indicative model using the European Commission’s PVGIS service for a 75kWp, south-facing Dublin array at a 30° tilt, with 14% system losses, estimates annual generation of about 72,900kWh.[3] For early planning, a reasonable broad range might be about 65,000–75,000kWh a year for a well-sited Irish system of this size. A site-specific model may produce a different result.
PVGIS models solar radiation and PV system performance by location and configuration.[2] Actual commercial solar energy generation depends on the building’s location, orientation, tilt, shading, module and inverter performance, downtime and weather. A roof facing east or west can still be useful, but its generation profile and annual yield will differ from the Dublin example. A proper proposal should use the site address and actual roof planes.
Potential electricity-bill savings and return on investment
Savings depend on how much solar power the business uses at the time it is generated and on the value of the electricity it would otherwise buy. Consider an illustration using 73,000kWh annual generation, 75% self-consumption, and an assumed avoided electricity price of €0.25/kWh:
73,000kWh × 75% × €0.25 = €13,687.50 estimated annual bill savings
This is an example, not a forecast. It excludes export payments, standing charges, demand charges, maintenance, financing, degradation, tax and changes in electricity prices. The 75% self-consumption assumption may be too high or too low for a particular load profile. Export income, if available, depends on the supplier arrangement and applicable terms and is not guaranteed.
Using the broad €67,500–€112,500 pre-grant cost range above, dividing by the illustrative €13,687.50 annual savings gives a simple pre-grant payback of roughly 4.9–8.2 years. This is a basic comparison rather than a full return-on-investment calculation. A business should use its actual half-hourly consumption data, quotation, grant offer, export terms and financing costs to estimate its own payback. Savings and payback periods are not guaranteed.
Installation, grid connection, maintenance and system life
A commercial solar project normally starts with a review of electricity bills or interval data, roof plans and business operating hours. The installer surveys the site, checks the roof and electrical infrastructure, designs the array and provides a quotation. The project then proceeds through grant and grid-connection steps, installation, testing, commissioning and handover.
The grid route depends on the system’s inverter AC rating, export capacity and the site connection—not just the panel DC capacity. ESB Networks publishes separate generation-connection processes, including application and technical-assessment steps for larger generators. The installer should confirm the applicable route and any export constraints before work begins. SEAI also states that the connection application is to be made before installing a system supported through its Non-Domestic Microgen Grant.[1]
After commissioning, monitoring can help identify faults or unexpected drops in output. Maintenance is generally a matter of checking the monitoring data, inspecting the system and responding to faults; the exact inspection plan depends on the site and installer. Ask for written product, inverter and workmanship warranty terms, as warranty periods differ by component and provider. Solar equipment can remain productive over many years, but output, repairs and component replacement should not be assumed to be cost-free or guaranteed.
Is your business roof suitable for a 75kW system?
Before deciding that a roof can take 75kWp, ask for a site-specific assessment that covers:
•The roof’s usable area after pathways, setbacks, obstructions and shading are mapped.
•Structural capacity, roof condition, waterproofing and likely remaining roof life.
•Module dimensions, mounting system, wind exposure and safe maintenance access.
•The business’s daytime load profile and desired level of self-consumption.
•Inverter capacity, grid connection, export limits and any electrical upgrades.
•Planning, building and fire-safety requirements that may apply to the particular property.
•The current grant offer and the timing of the works, if applying for support.
The roof-area figures in this article are useful for an initial conversation, not a substitute for engineering checks or a layout drawing. A structural assessment and professional survey protect the building and help ensure the proposal is technically and financially realistic.
Conclusion: plan your commercial solar assessment
A 75kW commercial solar system typically needs around 137–188 panels using the example module ratings above. The panel surfaces may total roughly 330–370m², while a safe and practical roof layout may call for substantially more clear roof area. The final answer depends on the module, roof type, access and design.
Generation, cost, grant support and payback also vary from one site to another. If your business is considering commercial solar panels in Ireland, contact LVP Renewables for a tailored commercial solar assessment and quotation. A site survey can establish the usable roof area, the right system size, the likely generation and the connection steps for your premises.
FAQs
How many solar panels are required for a 75kW commercial solar system?
It depends on the module wattage. Using the examples in this guide, the system needs about 188 × 400W, 167 × 450W, 150 × 500W or 137 × 550W panels. The final number depends on the chosen modules and system design.
How much roof space is needed for a 75kW solar installation?
The combined panel surface area is approximately 330–370m² for the example module sizes. Allow roughly 450–650m² of clear, usable roof for a compact layout as a preliminary estimate; tilted flat-roof layouts may need around 550–800m² or more. Pathways, setbacks, rooflights and structural constraints can change these figures.
How much does a 75kW commercial solar system cost in Ireland?
A broad 2026 indicative range is approximately €67,500–€112,500 before grants, based on €900–€1,500 per kWp. Roof condition, equipment, access, electrical work and grid requirements can move the final quotation. The current SEAI grant terms may reduce eligible project costs for approved applications, but support is not guaranteed.
How much electricity can a 75kW solar system generate in Ireland?
A 75kWp south-facing Dublin example modelled with PVGIS at 30° tilt and 14% system losses produces about 72,900kWh a year. A broad early estimate is 65,000–75,000kWh annually, but location, orientation, shading, weather and system efficiency all affect actual output.
