A standard domestic solar panel in Ireland measures 1,722mm by 1,134mm and weighs a little over 20kg. A slightly longer version, 1,762mm by 1,134mm, is becoming the new standard: 40mm longer, same width. Either way you are looking at a panel of roughly two square metres that one person can carry and two can lift onto a roof. That footprint has been stable for years. The wattage behind it has not, and that is the part that matters when you are working out what your roof can hold.
- Standard domestic panel: 1,722mm × 1,134mm × 30mm, about 20.8kg (LONGi Hi-MO)
- The emerging standard: 1,762mm × 1,134mm × 30mm, 20–22kg (JA Solar DeepBlue 4.0 Pro)
- Either is close to 2 m² per panel and about 11kg per m² on the roof
- A modern panel of that size makes 400–450W. The same rectangle made 300W in 2018
- Allow roughly 4.5 m² of panel per kWp, or 5–6 m² of roof once you allow for spacing and edges
- A typical 3-bed semi carries about 4.65 kWp on 21.1 m², which is ten or eleven panels
- The SEAI grant stops paying above 4 kWp, and you only get it once per MPRN
How Big Is One Solar Panel?
Two sizes cover almost every domestic installation in Ireland. PureVolt, an SEAI-registered installer working in Galway and Dublin, puts it plainly on its equipment guide: the standard domestic panel is 1,722mm by 1,134mm, and a slightly longer 1,762mm by 1,134mm is becoming prevalent as a new standard. Forty millimetres longer, identical width.
Those are not marketing numbers. They come straight off the manufacturers' own datasheets. LONGi lists its Hi-MO residential modules at 1,722 × 1,134 × 30mm and 20.8kg. JA Solar's product brochure gives its DeepBlue 4.0 Pro residential modules as 1,762 ±2mm × 1,134 ±2mm × 30 ±1mm at 20kg and 22kg depending on the variant. Same width, near-identical thickness, a few centimetres of difference in length.
| Panel | Dimensions | Area | Weight |
|---|---|---|---|
| LONGi Hi-MO (residential) | 1,722 × 1,134 × 30mm | 1.95 m² | 20.8kg |
| JA Solar DeepBlue 4.0 Pro | 1,762 × 1,134 × 30mm | 2.00 m² | 20–22kg |
| Large-format (commercial) | 2,333 × 1,134 × 30mm | 2.65 m² | 32.5kg |
| Largest utility modules | 2,465 × 1,134 × 35mm | 2.80 m² | 34.6kg |
The bottom two rows are there to head off a common confusion. Panels do get considerably bigger than the domestic standard, but the big ones are not what goes on a house. JA Solar's own brochure lists those 2.3 and 2.5 metre modules alongside the residential ones, and they weigh half as much again. PureVolt makes the same distinction: larger panels come out for commercial and business installations where there is a lot of roof to cover. On a semi-detached house in Ireland you are getting the 1.7 metre rectangle.
Same Rectangle, Almost Twice the Power
Here is what actually changed. A panel of these dimensions was a 300W panel in 2018. Today the same footprint carries 400 to 450W, and the 440W panel has become the reference unit for quoting Irish domestic systems. The efficiency gain happened inside the glass, through half-cut cells and better wafer technology, and it left the outside alone.
That has a consequence people rarely spell out. Every rule of thumb about how much roof you need per kilowatt was written for panels that no longer exist. You will still see 6 to 8 square metres per kWp quoted widely, including in older guidance. That was a fair figure for 300–350W panels. With a 440W panel at 2 m², a kilowatt-peak takes about 4.5 m² of actual panel.
Both numbers have a use. The 4.5 m² figure tells you how much glass goes up. The larger figure is closer to how much roof you should have available, because panels are not laid edge to edge: installers leave clearance at the eaves, the ridge and the verges, work around chimneys and roof lights, and keep clear of anything that shades. Allowing 5 to 6 m² of usable roof per kWp is realistic for a clean rectangular slope. Allow more if the roof is broken up.
What Fits on an Irish Roof
The useful way to answer this is not per square metre but per house, and PureVolt publishes exactly that: typical array sizes and the roof area they cover, by house type, for a south-facing roof in the middle of the country.
| House type | Typical array | Roof area covered | Panels (approx) |
|---|---|---|---|
| 2-bed mid-terrace | 3.72 kWp | 16.9 m² | 8–9 |
| 3-bed semi-detached | 4.65 kWp | 21.1 m² | 10–11 |
| 4-bed detached | 5.58 kWp | 25.3 m² | 12–13 |
| 6-bed detached | 7.44 kWp | 33.8 m² | 17 |
Run the arithmetic across that table and it holds together: 21.1 m² for 4.65 kWp works out at 4.54 m² per kWp, which is what you get from ten and a half 440W panels at 2 m² each. The panel count column is the same figure read the other way.
We have left the annual generation figures out of that table on purpose. The same installer quotes 860 kWh a year per kWp for a typical Irish home, but the per-house numbers published alongside these array sizes work out closer to 970 kWh per kWp, which is a best-case south-facing site rather than a typical one. Sizing is a roof-geometry question and yield is a location-and-orientation question, so we would rather send you to the sizing guide for output than quote a figure the source contradicts elsewhere on its own site.
These are areas of panel, on the half of the roof that faces the right way. A 3-bed semi has considerably more than 21 m² of total roof; what it has is roughly that much usable south-facing slope after the north side, the chimney and the edges come out. That is also why orientation changes the sums. PureVolt puts a south-east or south-west roof about 5% behind due south, and a due east or west roof about 20% behind per panel. An east-west roof does let you use both slopes, so you get double the area to work with. Our guide to solar panel direction in Ireland goes through that trade-off properly.
There is a second way to ask the sizing question: how many panels your electricity use justifies, rather than how many your roof holds. That calculation lives in our guide to how many solar panels you need in Ireland.
Will the Roof Take the Weight?
Almost always, yes, and the number is smaller than people expect. A 20.8kg panel covering 1.95 m² puts about 10.7kg on every square metre it covers. The heavier 22kg panel comes to around 11kg per m². Add the mounting rails and hooks and you are still in the region of 15kg per square metre spread across the rafters.
For context, that is less than the roof already carries in slate or concrete tile. The load is also distributed, not concentrated: the mounting system spreads it into the rafters at multiple fixing points rather than resting it on the covering. A ten-panel array adds somewhere around 210kg in panels, spread over roughly 20 m² of roof.
Where weight does come up is on older or unusual roofs: a tired farmhouse roof, a bungalow with lightweight sheeting, an old slate roof due for replacement anyway. That is a structural question for the installer's survey, not something to settle from a table. It is also a reason to get the roof done first if it is close to needing work, because taking an array off and putting it back is a cost you would rather not pay twice.
The Sizing Trap in the SEAI Grant
This is where panel size stops being a technical curiosity and starts costing money.
The SEAI Solar PV grant pays €700 per kWp up to 2 kWp, then €200 for every additional kWp up to 4 kWp, and caps at €1,800. It is paid pro rata, so a 2.5 kWp system draws €1,500. In practice that means €1,400 for 2 kWp, €1,600 for 3 kWp, and €1,800 for 4 kWp. Above 4 kWp the grant does not grow. SEAI has confirmed the maximum stays at €1,800 in 2026.
So the grant tops out at 4 kWp, while the table above says a typical 3-bed semi has room for 4.65 kWp and a 4-bed detached for 5.58 kWp. Most Irish roofs hold more than the grant will pay for. That is a fine reason to think carefully about the last few panels, which you fund yourself at close to full price.
SEAI states the grant "is not open to homes with previous funding for solar PV at this MPRN". Fitting a small array now to test the water, intending to grant-fund an extension in a few years, does not work. The second array gets no grant at all. If your roof has the room and the budget stretches, the panels beyond 4 kWp are cheaper to add on day one, while the scaffolding is up and the installer is already there, than to add as a separate job later with no grant behind them.
Two other limits sit above the grant. Your inverter's export capacity has to stay within 6 kW single-phase or 11 kW three-phase to use the free NC6 notification route, which our guide to the maximum solar system size in Ireland covers in detail. And to qualify for the grant at all the home must have an MPRN and have been built and occupied before 2021. Once you have grant approval you get 8 months to complete the works.
Panel dimensions are standard, so the thing worth comparing across quotes is how many the installer says your roof takes and where they propose to put them. Ask each one for a panel layout, not just a system size. Free quotes from SEAI-registered installers covering your county. No obligation, takes about 60 seconds.
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1,722mm by 1,134mm, about 30mm thick, weighing a little over 20kg. A slightly longer 1,762mm by 1,134mm panel is becoming the new standard, 40mm longer with the same width. Both work out at roughly 2 square metres per panel. LONGi lists its Hi-MO residential modules at 1,722 × 1,134 × 30mm and 20.8kg; JA Solar's DeepBlue 4.0 Pro is 1,762 × 1,134 × 30mm at 20–22kg.
About 4.5 m² of actual panel per kWp with modern 440W panels, or 5 to 6 m² of usable roof once you allow for spacing, edge clearance and obstructions. The widely quoted 6 to 8 m² per kWp is a legacy figure from the era of 300–350W panels and is now conservative. As a real-world check, an Irish 3-bed semi typically carries 4.65 kWp across 21.1 m² of covered roof.
Ten or eleven. A typical Irish 3-bed semi-detached house takes an array of about 4.65 kWp covering 21.1 m² of roof, which at 440W and 2 m² a panel is ten to eleven panels. A 2-bed mid-terrace runs closer to eight or nine panels, a 4-bed detached to twelve or thirteen.
Between 20 and 22kg for a domestic panel, which is about 11kg for every square metre of roof it covers. With mounting rails included the load is roughly 15kg per m², distributed into the rafters at multiple fixing points rather than resting on the slates. That is less than the roof already carries in slate or tile, so weight rarely rules an installation out. Older or lightweight roofs are a question for the installer's structural survey.
Barely. Domestic panels have grown 40mm in length in recent years and not at all in width, because the industry standardised on a 1,134mm wafer format. What has changed is output: the same rectangle that produced 300W in 2018 now produces 400 to 450W. Much larger modules of 2,333mm and 2,465mm do exist, but they are for commercial and utility installations, not houses.
Yes, and most Irish roofs have the room. The grant pays €700 per kWp to 2 kWp then €200 per additional kWp to 4 kWp, capping at €1,800, while a typical 3-bed semi holds 4.65 kWp and a 4-bed detached 5.58 kWp. Panels beyond 4 kWp are funded entirely by you. The separate limit to watch is grid export capacity: 6 kW single-phase or 11 kW three-phase keeps you on the free NC6 route.
No. SEAI states the grant is not open to homes with previous funding for solar PV at the same MPRN, so a second array attracts no grant. Panels you might want eventually are cheaper to fit at the outset, while the scaffolding is up and the installer is on site, than to add later as a standalone job with no grant support. If the roof has the space, size for where you expect to be rather than where you are.
Sources: LONGi — Hi-MO residential modules — module dimensions 1,722 × 1,134 × 30mm; Hi-MO 6 430W listed at 20.8kg. JA Solar — product brochure (PDF) — DeepBlue 4.0 Pro residential modules 1,762 ±2mm × 1,134 ±2mm × 30 ±1mm at 20kg and 22kg; larger modules 2,333 × 1,134 × 30mm at 32.5kg and 2,465 × 1,134 × 35mm at 34.6kg. PureVolt Solar — guide to solar panels (2026) — standard domestic panel size 1722mm x 1134mm with 1762mm x 1134mm becoming a new standard; larger panels used on commercial installations; typical array size and roof area covered by house type (2-bed mid-terrace 3.72 kWp / 16.9 m²; 3-bed semi 4.65 kWp / 21.1 m²; 4-bed detached 5.58 kWp / 25.3 m²; 6-bed 7.44 kWp / 33.8 m²); 1 kWp generating about 860 kWh a year in Ireland; south-east and south-west roofs about 5% behind due south, east and west about 20% behind per panel with double the usable area. Two notes on that source: it describes the 1,762mm panel as "60mm longer" than the 1,722mm one, which is a 40mm difference, and we have used the measured figure; and its per-house annual generation figures (3,617 / 4,521 / 5,423 / 7,156 kWh) imply about 970 kWh per kWp against its own headline figure of 860 kWh per kWp, so we have not reproduced them. SEAI — Solar electricity grant (solar PV) — €700 per kWp up to 2 kWp, €200 for every additional kWp up to 4 kWp, capped at €1,800, paid pro rata (2.5 kWp = €1,500); maximum remaining at €1,800 in 2026 as confirmed by Minister O'Brien; MPRN required, home built and occupied before 2021, grant not open to homes with previous funding for solar PV at this MPRN; 8 months to complete works after approval. Panel areas and per-square-metre loadings are calculated from the dimensions and weights above. Manufacturer specifications vary by model and change between product generations — check the datasheet for the exact panel on your quote. All sources checked 7 August 2026.
Published: 7 August 2026. Author: Neil Russell.