20kw solar system can be a practical option for a farm, workshop, warehouse, office, retail premises or large property with significant electricity demand. At this size, the installation can produce a meaningful amount of renewable electricity, particularly when the building uses power during daylight hours.
The price depends on much more than the number of panels. Roof condition, mounting equipment, inverter design, electrical works, scaffolding, grid connection requirements and battery storage can all change the final quotation. A 20kW system for a business or farm is also treated differently from a large system proposed for a private home when grants and connection requirements are considered.
This guide explains the likely 20kw solar system price in Ireland, how many panels are needed, how much roof space is required, how much energy the system may produce and which supports may be relevant.
What is a 20kW solar system?
A solar PV system is usually described by its capacity in kilowatts peak, or kWp. A 20kWp array has panel ratings that add up to at least approximately 20,000 watts under standard test conditions.
The capacity is not the same as the amount of electricity generated. The difference is:
•kW or kWp: the system’s rated power capacity at a point in time.
•kWh: the quantity of electricity generated or consumed over a period.
A 20kW solar panel system will not produce 20kW continuously. It generates during daylight, and its output rises and falls with sunlight, cloud, temperature, orientation, shading and system losses. In Ireland, SEAI notes that around 75% of solar PV generation occurs between May and September.
A 20kW system is often used in two different settings:
•Large domestic property: a home with unusually high demand from heat pumps, electric vehicles, electric heating, home offices or other loads.
•Commercial or agricultural property: a farm, workshop, warehouse, office, school, retail unit or community building with regular daytime electricity use.
For an ordinary home, 20kW may be significantly larger than the property’s typical demand and available roof space. For a business or farm, it may be a modest system that offsets only part of the daytime load.
20kW solar system price in Ireland
As a current planning guide, industry pricing information for Ireland places a standard commercial rooftop installation of around 20kWp at approximately €18,000–€34,000 before grants, depending on equipment, roof complexity and electrical works. A second 2026 industry guide gives a narrower standard rooftop range of approximately €20,000–€30,000 before grants for a 20kWp system.
These are indicative market ranges, not an official price list or a quotation from LVP Renewables. A straightforward large roof may sit nearer the lower end. A difficult roof, long cable route, structural reinforcement, specialist switchgear or a complicated grid connection can push the price higher.
For a more useful budget, ask a quotation to separate the following items:
•Solar panels and mounting system.
•Inverter or inverters and monitoring equipment.
•Design, engineering and system modelling.
•Scaffolding, access equipment and labour.
•Roof repairs or structural reinforcement.
•Cabling, protection, switchgear and electrical upgrades.
•ESB Networks connection work or export limitation equipment.
•Commissioning, documentation and after-sales support.
•Battery storage, if included.
•VAT and any grant shown separately.
A 20kW solar system cost in Ireland should be compared on a like-for-like basis. A cheaper quote may exclude scaffolding, electrical upgrades, monitoring, structural work or a battery. Check the panel and inverter warranties, expected annual generation and the assumptions behind the financial model before comparing totals.
Domestic versus commercial pricing
A 20kW system installed on a private dwelling may be more expensive per kWp than a commercial rooftop system because the roof is often more fragmented and access is less efficient. It may also need several roof faces, multiple strings or specialist optimisers.
Commercial solar panels in Ireland are often installed on large, uncomplicated roofs. The installer can use longer rows, more efficient access arrangements and larger electrical equipment. However, commercial projects may involve three-phase supplies, larger switchboards, structural surveys and more detailed export or connection assessments.
How many panels are needed for a 20kW system?
The calculation is:
20,000 watts ÷ panel wattage = panel quantity
The result is rounded up to the next whole panel where necessary so that the array reaches at least 20kWp.
Panel rating: 350W
Calculation: 20,000 ÷ 350 = 57.14
Approximate panel count: 58 panels
Resulting capacity: 20.30kWp
Panel rating: 400W
Calculation: 20,000 ÷ 400 = 50
Approximate panel count: 50 panels
Resulting capacity: 20.00kWp
Panel rating: 450W
Calculation: 20,000 ÷ 450 = 44.44
Approximate panel count: 45 panels
Resulting capacity: 20.25kWp
Panel rating: 500W
Calculation: 20,000 ÷ 500 = 40
Approximate panel count: 40 panels
Resulting capacity: 20.00kWp
Panel rating: 550W
Calculation: 20,000 ÷ 550 = 36.36
Approximate panel count: 37 panels
Resulting capacity: 20.35kWp
The exact design may use a slightly different capacity. Panel ratings do not always divide evenly into 20,000 watts, and roof layout or inverter compatibility may be more important than achieving an exact number. The quotation should state the number of panels, the individual panel rating, total DC capacity in kWp and inverter AC capacity.
20kW solar panel size and roof space
The physical size of a 20kw solar panel varies by manufacturer. Many current panels are approximately 1.7–2.0 metres long and around 1.1 metres wide. For an early estimate, using about 1.9m² per panel gives the following panel surface areas:
•350W panels: approximately 58 panels, covering about 110m².
•400W panels: approximately 50 panels, covering about 95m².
•450W panels: approximately 45 panels, covering about 86m².
•500W panels: approximately 40 panels, covering about 76m².
•550W panels: approximately 37 panels, covering about 70m².
These figures describe the combined panel surface only. The total usable roof area must also allow for roof edges, maintenance access, mounting clearances, walkways, skylights, vents, rooflights, valleys, chimneys and shaded sections.
As a broad early planning allowance, a 20kW rooftop installation may need around 85–145m² of suitable usable roof area. The lower end may be possible on a clean, efficient commercial roof using higher-wattage panels. A complicated roof may require more area or may not be able to accommodate the full array.
SEAI gives a worked commercial example in which a 30kWp installation uses about 125m², although actual panel dimensions and layout vary. A site survey is therefore essential before treating any roof-space estimate as final.
Roof orientation and pitch also affect the design. South-facing panels can provide strong annual production, while east- and west-facing roofs can spread generation into the morning and afternoon. Shading from trees, buildings, chimneys or roof structures should be modelled rather than estimated by eye.
How much power does a 20kW solar system produce?
The question “how much power does a 20kw solar system produce?” needs two answers: the system’s maximum rated capacity and its energy generation over time.
The maximum rated capacity is approximately 20kW or 20kWp. Annual energy generation is measured in kWh and is lower than 20kW multiplied by every hour of the year because the panels do not operate at their rated output continuously.
SEAI states that a well-located 3kW system using around 20m² can generate about 2,600kWh per year. That equates to roughly 867kWh per kWp. Applying a similar benchmark to 20kWp gives approximately 17,000kWh per year.
A reasonable early planning range for many Irish locations is approximately 15,000–18,000kWh per year, subject to the exact site and system design. Using that range, the average generation would be approximately:
•Daily average: 41–49kWh across the year.
•Monthly average: 1,250–1,500kWh across the year.
•Annual generation: 15,000–18,000kWh.
These are averages, not a daily promise. Summer months can produce much more than the annual daily average, while winter production can be much lower. SEAI notes that Irish PV systems still operate on overcast days, but not at their maximum rated capacity.
Generation is affected by:
•County and local solar resource.
•Roof direction and pitch.
•Shading and obstructions.
•Panel efficiency and inverter performance.
•Temperature, dirt and downtime.
•Cable and battery losses.
An installer should provide a location-specific generation estimate and explain the assumptions used.
Factors that affect the 20kW solar system price
Two 20kW systems can have very different prices. The main factors include the following.
Panel brand and efficiency
Higher-efficiency panels can produce more power from a limited roof area. Premium products may include longer product warranties, improved temperature performance or specialist construction, but a higher price does not automatically produce a better financial return.
Inverter capacity and design
The inverter converts the panels’ DC electricity into AC electricity for the building. The design may use one larger inverter or several smaller units, depending on roof orientations, strings, monitoring and redundancy. A commercial site may require three-phase equipment.
Roof and mounting equipment
A pitched roof, flat roof, agricultural shed and ground-mounted array each need different mounting solutions. Flat roofs may require ballasted or mechanically fixed systems. Ground-mounted projects can add foundations, fencing, trenching and civil works.
Electrical work and grid connection
The main switchboard, cable routes, protection, export capacity and supply arrangement can materially affect price. ESB Networks defines micro-generation as up to 6kVA on single phase or 11kVA on three phase. A 20kW project may therefore need a different connection assessment rather than being treated as a standard micro-generation installation.
Monitoring, warranties and support
Monitoring allows the owner to compare actual performance with the expected output. Include inverter, panel, workmanship and battery warranties in the quotation, along with the process for fault reporting and replacement.
SEAI solar grants and funding in Ireland
Grant eligibility depends on the property type and scheme rules. A 20kW system should not be assumed to qualify simply because solar PV grants exist.
Domestic support
The current SEAI domestic solar PV grant provides up to €1,800 for eligible homes. A separate battery grant of €600 may also apply. The domestic scheme page states that the home must have an MPRN, must have been built and occupied before 2025 and must not have previously received solar PV funding at that MPRN.
The domestic solar grant is capped at 4kWp, so it does not fund the full cost of a 20kW domestic array. It is also necessary to receive the grant offer before work begins and to use the applicable registered company.
Non-domestic support
Businesses, farms, public-sector bodies, schools, community centres and non-profit societies may be eligible for the SEAI Non-Domestic Microgen Grant. The scheme supports systems up to 1,000kWp.
The current SEAI scheme page states that, for new applications made from 6 October 2026 to 6 July 2027, support is increased to an effective 45% rate, subject to scheme conditions. Its published rate table lists €600 per kWp for systems from 7kWp to 20kWp, meaning a 20kWp system has a calculated grant value of €12,000 before applying any lower-of-cost or scheme limitations. The payment is the lower of the grant amount shown in the application summary and 45% of the invoiced cost.
Grant windows, rates and eligibility can change. Apply through the official SEAI process, wait for the letter of offer and do not start work before the required approval. A quotation should identify whether the grant is domestic or non-domestic and show the gross price and assumed grant separately.
20kW solar system with battery storage
A battery stores surplus solar electricity for later use. It can charge during the day and discharge when the building needs electricity in the evening or overnight. This can increase self-consumption and reduce imported electricity.
Battery storage does not increase the amount of sunlight available or remove the need to size the PV array properly. Charging and discharging also cause energy losses, and the battery adds capital cost, controls and future replacement considerations.
Battery capacity should be based on the building’s load profile. A farm or business with substantial evening demand may benefit from a larger battery than an office that is empty after 6pm. Consider usable capacity, power rating, warranty, cycle life, fire protection, backup capability and whether the system can be expanded later.
SEAI explains that batteries can increase the proportion of solar electricity used on site, but they increase the system cost and some energy is lost through the charge-discharge cycle.
Electricity bill savings and export payments
Solar reduces the amount of electricity purchased from the grid when the building is using power. The value of each kilowatt-hour used directly is generally linked to the import tariff that would otherwise have been paid.
Daytime consumption is therefore important. A farm running pumps, a workshop operating machinery or a warehouse using refrigeration may use a large share of solar electricity as it is generated. A property with low daytime demand may export more electricity or need a battery to shift generation into the evening.
Excess generation may be exported, subject to the suitable ESB Networks connection and the electricity supplier’s arrangements. SEAI explains that the Clean Export Guarantee is paid by the electricity supplier at a competitive market rate, and that a smart meter allows exported electricity to be measured accurately. Export rates vary by supplier and can change, so they should not be treated as a permanent fixed income.
20kW solar system payback period: a worked example
The solar system payback period is estimated by dividing the net installation cost by the annual financial benefit. It is not a guarantee because electricity prices, export rates, generation, maintenance and usage can change.
Consider this hypothetical non-domestic example:
•Gross 20kWp rooftop installation: €28,000.
•Assumed eligible grant: €12,000, subject to the scheme rules and grant offer.
•Net capital cost: €16,000.
•Annual generation: 17,000kWh.
•Direct on-site use: 70%, or 11,900kWh.
•Avoided electricity cost: €0.30/kWh.
•Exported electricity: 5,100kWh.
•Hypothetical export value: €0.10/kWh.
The illustrative annual benefit would be:
•Direct-use saving: 11,900 × €0.30 = €3,570.
•Export income: 5,100 × €0.10 = €510.
•Total annual benefit: €4,080.
•Simple payback: €16,000 ÷ €4,080 = approximately 3.9 years.
This example is deliberately hypothetical. The assumed grant, import rate, export value, generation and self-consumption must be replaced with the figures in a property-specific quotation. Finance costs, maintenance, inverter replacement, battery costs and tax treatment are not included.
Is a 20kW solar system suitable for your property?
A 20kW solar panel installation may be suitable for:
•Farms and agricultural sheds.
•Workshops and manufacturing units.
•Warehouses and distribution premises.
•Offices, retail premises and hospitality buildings.
•Schools, community centres and other non-profit sites.
•Larger homes with heat pumps, EV charging and high electricity use.
Suitability depends on more than roof size. Review at least 12 months of electricity bills or half-hourly consumption data. Check the roof structure, available unshaded area, electrical supply, grid connection, planning requirements and whether the expected solar output matches the building’s load profile.
Planning a 20kW solar panel installation
The normal process includes:
1.Review electricity bills and future demand, including EVs and heat pumps.
2.Survey the roof, ground area, orientation, shading and structure.
3.Design the panel layout, strings, inverter and battery if required.
4.Confirm electrical and ESB Networks requirements.
5.Check the relevant SEAI grant and apply before work starts.
6.Compare written quotations and expected generation.
7.Complete the connection process and install the system.
8.Test, commission and receive the safety file and warranties.
9.Set up monitoring and compare actual generation with the forecast.
For non-domestic work, ESB Networks states that the inverter must comply with IS EN50549-1 with the current Irish settings and that installation must be completed by a registered electrical contractor following the applicable connection process.
How to choose a solar installer in Ireland
Compare installers on the complete system rather than only on the 20kW solar system price. Ask for:
•Panel and inverter model numbers.
•Total array capacity in kWp and inverter AC rating.
•Expected annual generation and modelling assumptions.
•Roof loading, mounting and access details.
•Electrical and grid connection responsibilities.
•Battery capacity and backup specification, if applicable.
•Product, workmanship and installation warranties.
•Monitoring arrangements and after-sales support.
•Grant eligibility and the required application timetable.
For grant-supported work, use the relevant SEAI-registered company. SEAI advises applicants to compare quotes, check references and request a written contract showing the work, price, payment terms and warranties.
Conclusion
The 20kw solar system price in Ireland depends on system design, equipment, roof complexity, electrical work and whether battery storage is included. As an early commercial planning range, a standard 20kWp rooftop installation may cost approximately €18,000–€34,000 before grants, but the only reliable price is a site-specific quotation.
A 20kW system could use around 37–58 panels depending on panel wattage and may require approximately 85–145m² of usable roof area. A broad Irish planning estimate for generation is around 15,000–18,000kWh per year, subject to the property’s location, orientation, shading and system efficiency.
Domestic and non-domestic grant rules are different. A large home may receive only the applicable capped domestic support, while an eligible business or farm may qualify under the Non-Domestic Microgen Grant. Review electricity demand, self-consumption, export arrangements and the grid connection before deciding on system size.
Visit LVP Renewables to request a tailored solar quotation for your home, farm or commercial property.
FAQs
How much does a 20kW solar system cost in Ireland?
A standard commercial rooftop 20kWp installation may cost approximately €18,000–€34,000 before grants, based on current industry pricing guides. Difficult roofs, electrical upgrades, structural work, ground mounting and batteries can increase the price. A site survey is needed for an accurate quotation.
How many panels are needed for a 20kW solar system?
The number depends on panel wattage. A 20kW system may use approximately 58 panels at 350W, 50 panels at 400W, 45 panels at 450W, 40 panels at 500W or 37 panels at 550W. The final capacity may be slightly above 20kWp.
How much power does a 20kW solar system produce?
A 20kW system has a rated capacity of approximately 20kWp. In Ireland, a broad early planning estimate is around 15,000–18,000kWh of annual generation, or roughly 41–49kWh per day averaged across the year. Actual output varies by location, roof direction, pitch, shading, weather and equipment.
Can you get an SEAI grant for a 20kW solar system in Ireland?
Possibly, but the answer depends on the property type and scheme. The domestic solar PV grant is capped at €1,800 and covers up to 4kWp, so it does not fund the full 20kW array. Eligible businesses, farms and other non-domestic applicants may be able to apply under the SEAI Non-Domestic Microgen Grant, subject to current rates, eligibility and approval before work begins.
