---
title: "Solar panel weight per square metre on a roof | ComparePV"
description: "Module weight per square metre from every datasheet in our catalogue, what rails and ballast add, and how to hold the total against what your roof can carry."
source: "https://comparepv.com/articles/how-much-does-a-solar-array-weigh"
image: "https://comparepv.com/static/images/og/articles/how-much-does-a-solar-array-weigh.jpg"
updated: 2026-10-09
---

# How much weight do solar panels add to a roof?

Module weight per square metre from every datasheet in our catalogue, what rails and ballast add, and how to hold the total against what your roof can carry.

By [Bart Szablowski](https://comparepv.com/authors/bart-szablowski) · Updated 9 October 2026 · 8 min read


## The analysis

On this page

1. Weight per module and weight per square metre
2. What the catalogue says
3. Mounting adds its own load
4. Pitched roof or ballasted flat roof
5. When to get a structural check
6. What to do with this when you buy
7. What these figures can't tell you

Figures and denominatorsRelated readingReferences

**In short:** the median module in our catalogue weighs 26.5 kg and covers 2.22 m², which works out at a median of 11.5 kg per square metre of roof it covers. In two structural reports from one mounting maker, the rails on a pitched roof add about a kilogram per square metre, while the ballast on a flat roof weighs more than the modules themselves. Ask what your roof can take per square metre, not per module.

A datasheet gives weight per module, because that is what someone lifts. A roof doesn't care about one module. It carries a load spread over its surface, and a structural engineer will ask how many kilograms, or kilonewtons, land on each square metre. This article turns the first figure into the second, then adds what the datasheet leaves out.

![Top view of a square concrete paver laid as ballast on an aluminium mounting rail and plastic foot on a black flat-roof membrane](https://comparepv.com/static/images/articles/flat-roof-ballast-paver-on-rail.webp)

*A concrete paver laid as ballast on the rail of a flat-roof mounting system before the modules go on: on a ballasted roof this weight, not screws, holds the array down. Image: [Asurnipal](https://commons.wikimedia.org/wiki/File:Sulz-ASZ_Vorderland-aluminum_substructures_photovoltaic_modules-PMT_EVO_2-1_EW-ballast-01ASD.jpg), [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0).*

### Weight per module and weight per square metre

Weight per module mostly follows the size of the module. A bigger frame holds more glass, more cells and more aluminium, so it weighs more. In the catalogue the median module is 26.5 kg, with the 10th percentile at 20.3 kg and the 90th at 35.0 kg, and 55 % of modules are over 25 kg. The [article on module sizes](https://comparepv.com/articles/how-big-are-modern-solar-panels) covers what that means for lifting.

Divide each module's weight by its area and most of the frame size drops out. What's left is how the module is built: the glass on the front, the frame, and either a polymer sheet or a second pane of glass on the back. PVEducation's page on module materials describes the usual stack: tempered glass in front, an aluminium frame, a thin polymer backsheet behind.

| Figure | 10th percentile | Median | 90th percentile |
| --- | --- | --- | --- |
| Weight per module | 20.3 kg | 26.5 kg | 35.0 kg |
| Weight per square metre | 10.5 kg/m² | 11.5 kg/m² | 12.5 kg/m² |

Read the table across, not down. Divide each 90th percentile by its median, then do the same for the 10th. Whichever row moves less from its median is the figure you can plan with before you have picked a module.

### What the catalogue says

Of 14,005 modules, 13,880 state a weight, a length and a width that pass the sanity checks, so they have a weight per square metre. Rated power per kilogram is the other way to look at the same datasheets: the median is 18.8 W/kg. If you size the system in kilowatts, divide its watts by that figure to get a first guess at the module weight before you have chosen a model.

#### Glass on the back weighs more than a backsheet

A bifacial module needs a back that lets light through, which usually means glass on both faces. The catalogue splits weight per square metre by that build:

| Build | Modules | Weight per square metre, median |
| --- | --- | --- |
| Listed as bifacial | 7,743 | 12.2 kg/m² |
| Not listed as bifacial | 6,262 | 10.8 kg/m² |

The gap between the two medians is what the second pane costs per square metre, on paper. Check the Modules column before you trust the gap: a median over a few dozen modules can move with one manufacturer's datasheets. Whether the rear side earns its weight back in yield is a separate question, covered in [is a bifacial solar panel worth it](https://comparepv.com/articles/is-a-bifacial-solar-panel-worth-it).

### Mounting adds its own load

The datasheet weight is the module alone. Between the module and the roof sit clamps, rails and the hooks or feet that carry them, and on a flat roof often a lot of concrete.

Mounting manufacturers' planning software prints this in a structural report for each job. Two K2 Systems reports, posted publicly by the shops that sold the kits, show the scale:

- **Pitched roof.** A SolidRail array on a 35 degree tiled roof: the modules weigh 10.91 kg/m², the mounting system 1.25 kg/m², and the report gives a total dead load of 0.12 kN/m² without ballast.
- **Flat roof.** An S-Dome 6 ballasted array of six modules on a garage roof: the modules weigh 10.98 kg/m² and the mounting system 2.25 kg/m² before ballast. The ballast plan then adds 346.5 kg of ballast for six modules of 1.82 m² each, which is about 32 kg for every square metre of module.

Two jobs aren't a survey, and your installer's report is the one that counts. But the pattern holds as a rule of thumb. On a pitched roof the mounting is a small addition to the modules. On a ballasted flat roof the ballast can outweigh the modules, about three times over in that report.

#### Kilograms and kilonewtons

Structural reports and building codes work in kilonewtons per square metre. One kilogram weighs 9.81 newtons, so multiply kg/m² by 9.81 and divide by 1000 to get kN/m². A load of about 102 kg/m² is 1 kN/m², which is why the pitched-roof report above turns roughly 12 kg/m² into 0.12 kN/m².

### Pitched roof or ballasted flat roof

#### Pitched roof: hooks into the rafters

On a pitched roof, hooks under the tiles are screwed into the rafters, rails run across the hooks and the modules clamp onto the rails. The array is held down by the screws, so it needs no extra weight. The load per square metre is roughly the module figure plus the mounting.

The same K2 report puts that dead load next to the snow load for its site: 0.575 kN/m² of snow on the roof, against 0.12 kN/m² of array. That's one site in one snow zone, and snow isn't new: the roof was meant to carry it before the array went up. But it shows the size of the question, and it's why snow load and wind load sit in the same structural report as the dead weight.

#### Flat roof: weight instead of screws

On a flat roof, installers often avoid drilling through the waterproofing. The array then stays put because it is heavy: concrete blocks or pavers sit in trays on the frame, like the one in the picture above. How much depends on wind at the site, the height of the building, the roof edge and the friction between the feet and the membrane. The ballast plan is calculated for each roof, and the corners and edges, where wind pulls hardest, get the most.

Two things follow. A ballasted array can weigh several times what the same modules weigh on rails, so the roof check matters far more there. And the load isn't spread evenly. Edge rows carry more ballast than middle rows, and the weight lands on the feet and the strips under them, not evenly across the deck. The K2 flat-roof report gives 0.34 kN/m² for the module block itself and 0.20 kN/m² averaged over the roof area. Ask which of the two your engineer's figure means.

#### Try your own numbers

Set the number of modules and switch between the two roof types. Module weight and area start on the catalogue medians. Mounting, ballast and the allowance are example inputs, so type the ones from your own quote.

**What the array puts on each square metre of roof**

Set the modules, their weight and area, the mounting and, for a flat roof, the ballast, and see the total weight and the load per square metre against an allowance you type.

Divide the module weight by its area to get the modules' load per square metre, then add the mounting and any ballast, both already per square metre. A 22 kg module of 2 m² is 11 kg/m²; with 1.5 kg/m² of rails on a pitched roof that is 12.5 kg/m², or 0.12 kN/m². The same modules ballasted on a flat roof with 2.5 kg/m² of frame and 30 kg/m² of concrete come to 43.5 kg/m², over three times as much. Ten or forty modules give the same load per square metre; only the total in kilograms changes.

Interactive on the web page.

Moving the module count changes the total kilograms and leaves the load per square metre where it was. A roof that is over its allowance per square metre stays over with fewer modules. It needs a lighter build, a different fixing, or a stronger roof.

### When to get a structural check

In Europe, roof loads are designed to EN 1991-1-1, the Eurocode part on densities, self-weight and imposed loads for buildings, with EN 1991-1-3 for snow and EN 1991-1-4 for wind. A solar array is extra self-weight that sits on the roof all the time. What a roof was designed for depends on the country, because each national annex sets its own values. For roofs reached only for maintenance, the imposed load is a national choice. The Danish annex, for example, sets the spread imposed load on such roofs at zero, keeps a 1.5 kN point load, and drops both whenever snow is on the roof. So there's no single European figure you can hold your array against.

Get the roof checked by a structural engineer before you build when:

- **The roof is flat and the array is ballasted.** That is when the extra load can be several times the modules' own.
- **The building is old, or nobody has its drawings.** Timber that has sagged or been cut for a roof window has less margin than the original design.
- **The roof is light by design.** Sheet-metal and sandwich-panel roofs on sheds, garages and halls are built close to their limits.
- **You are in a heavy snow area** or the array creates a step where snow can drift.
- **The array covers only part of a roof plane.** The load lands on some rafters or purlins and not on others.

On an ordinary pitched roof in sound condition, an installer may judge the load from a site visit rather than a full calculation. That's their call to make, and it should come in writing.

### What to do with this when you buy

1. Ask your installer for the load in kg/m² or kN/m², modules and mounting together, and for flat roofs including ballast. A total in kilograms alone doesn't answer the question.
2. Take the module's weight and area from its datasheet ([how to read one](https://comparepv.com/articles/how-to-read-a-solar-panel-datasheet)) and divide. If the result sits far from the catalogue median of 11.5 kg/m², check the datasheet figures before anything else.
3. For a ballasted flat roof, ask for the ballast plan, not just a total. It shows where the heavy rows are.
4. If you need to save weight, compare two figures: the catalogue's spread per square metre, from 10.5 to 12.5 kg/m², and the ballast in your plan. Whichever is larger is where the weight can come off.

The number of modules is a separate question, covered in [how many solar panels a household needs](https://comparepv.com/articles/how-many-solar-panels-does-a-household-need). The [roof-fit selector](https://comparepv.com/tools/roof-fit-selector) works out how many fit.

### What these figures can't tell you

Datasheet weights are nominal, and an engineer will use the weight on the specific datasheet, not a median. Our figures stop at the module: cables, inverters, optimisers and walkways are not in them. The two mounting figures come from two real jobs, not a survey of mounting systems. And whether your roof can take the load depends on the building, which no catalogue knows.


## 01. Figures and denominators

How the figures above were computed. Every figure is recomputed from the catalogue and the live shop offers when the page is served, and each one counts only the modules or offers that publish the value.

The pool is every listable module in our catalogue, as each manufacturer's datasheet states it. One datasheet usually covers a whole power ladder of the same frame, so the figures count modules, not datasheets.

Weight per module counts when the datasheet weight is between 1 and 100 kg; that is 13,987 modules. Area is the outer length times the outer width, frame included, counted when the length is between 500 and 3000 mm and the width between 300 and 1500 mm.

Weight per square metre is the datasheet weight divided by that area, for the 13,880 modules that state all three figures. A result outside 5 to 25 kg/m² is left out: no framed module is built that light or that heavy, so a figure out there is a dimension in the wrong unit or a weight from the packing list. The bifacial split uses the same figure and the same range, by whether the catalogue lists the module as bifacial.

All medians and percentiles are continuous percentiles over the modules that state the figure. Mounting and ballast weights are not in our catalogue; the figures for them in the text come from the two manufacturer reports in the sources, and the ones in the interactive figure are example inputs.


| Figure | Value | Computed over |
| --- | --- | --- |
| Module weight, median | 26.5 kg | 13,987 modules |
| Module area, median | 2.22 m² | 13,990 modules |
| Module weight per square metre, median | 11.5 kg/m² | 13,880 modules |
| Module weight, 10th percentile | 20.3 kg | 13,987 modules |
| Module weight, 90th percentile | 35.0 kg | 13,987 modules |
| Share of modules heavier than 25 kg | 55 % | 13,987 modules |
| Module weight per square metre, 10th percentile | 10.5 kg/m² | 13,880 modules |
| Module weight per square metre, 90th percentile | 12.5 kg/m² | 13,880 modules |
| Modules in the catalogue | 14,005 | 14,005 modules |
| Modules stating weight, length and width | 13,880 | 14,005 modules |
| Rated power per kilogram, median | 18.8 W/kg | 13,987 modules |
| Modules listed as bifacial | 7,743 | 14,005 modules |
| Bifacial modules: weight per square metre, median | 12.2 kg/m² | 7,735 modules |
| Modules not listed as bifacial | 6,262 | 14,005 modules |
| Monofacial modules: weight per square metre, median | 10.8 kg/m² | 6,145 modules |
| Modules stating a weight | 13,987 | 14,005 modules |


## 02. Related tools

[Roof-fit selector](https://comparepv.com/tools/roof-fit-selector)


## 03. Related reading


#### How big are modern solar panels

[Open](https://comparepv.com/articles/how-big-are-modern-solar-panels)

Length, width, weight, watts per square metre and per kilogram for every module in our catalogue, and what the common formats mean for roofs and lifting.


#### Is a bifacial solar panel worth it?

[Open](https://comparepv.com/articles/is-a-bifacial-solar-panel-worth-it)

When the back of a bifacial module pays off, ground mount or roof, how bifaciality factors are spread in our catalogue and what bifacial modules cost per watt.


#### How many solar panels does a household need

[Open](https://comparepv.com/articles/how-many-solar-panels-does-a-household-need)

Yearly kWh, your site's yield in kWh/kWp and one module's power give the module count. Worked for Warsaw, Munich and Seville, with the catalogue spread.


#### How to read a solar panel datasheet

[Open](https://comparepv.com/articles/how-to-read-a-solar-panel-datasheet)

A field by field guide to the solar module datasheet, with typical values from our catalogue and three arithmetic checks that catch a figure that is wrong.


## 04. Reference list

1. [European Commission Joint Research Centre, Eurocode 1, Actions on structures, EN 1991-1-1 densities, self-weight, imposed loads for buildings](https://eurocodes.jrc.ec.europa.eu/EN-Eurocodes/eurocode-1-actions-structures)
2. [Danish Standards, National Annex to EN 1991-1-1, imposed loads on roofs of category H (clause 6.3.4.2, Table 6.10)](https://www.ds.dk/media/mv5dsp34/ds-en-1991-1-1-dk-na-2013-english.pdf)
3. [K2 Systems, K2 Base structural report for a SolidRail array on a 35 degree tiled pitched roof (2023), dead load and snow load sections](https://www.heima24.de/shop/images/products/media/K2-8kwp-waag.pdf)
4. [K2 Systems, K2 Base structural report for an S-Dome 6 ballasted array on a flat garage roof (2022), dead load and ballast sections](https://www.photovoltaik4all.de/media/56/1d/e8/1694533420/einzelgarage-s-dome-6-3x2_report.pdf)
5. [PVEducation, Module materials](https://www.pveducation.org/pvcdrom/modules-and-arrays/module-materials)


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Source: https://comparepv.com/articles/how-much-does-a-solar-array-weigh