Roof Load Reference
How much do solar panels weigh per m²?
A rail-mounted commercial array adds roughly 15 to 25 kg/m² of dead load over the array footprint. A ballasted flat-roof system is heavier, typically 30 to 60 kg/m². A single panel is about 25 kg. The figures below are verified to the Eurocodes, with one caveat that matters: weight alone never tells you whether a roof can carry an array.
Modules at roughly 11 to 13 kg/m², plus rails, clamps and fixings. Dead load to BS EN 1991-1-1. The lightest framed systems sit near 12 kg/m².
Panels, frame and ballast together. The ballast holds the array down against wind uplift, so the quantity is set by the wind calculation under BRE Digest 489 and scales with exposure.
A 470 W module is roughly 22 kg; a large-format 650 W module is around 34.6 kg. Most current commercial modules sit between 25 and 30 kg.
Conversion: 1 kN/m² is about 102 kg/m².
These are typical, indicative figures. The actual figure depends on the specific system and the manufacturer's datasheet, and whether any given roof can carry it requires a project-specific structural assessment.
Why kg/m² is not the whole answer
The weight a solar array adds is the easy part to quote. It is also only one of three loads an engineer has to resolve before a roof can be signed off. The dead load above is the added permanent weight over the array footprint, the area the panels cover, on top of the roof's existing self-weight. It is not spread over the whole roof, and it is not the full picture.
Dead load
The permanent weight of panels, frame and ballast. The kg/m² figures above. Assessed to BS EN 1991-1-1.
Snow load
Variable by site, altitude and drift. Can exceed the array weight on an exposed UK roof. BS EN 1991-1-3.
Wind uplift
Acts to lift the array and load the fixings. The reason ballasted systems get heavier. BS EN 1991-1-4 and BRE Digest 489.
These are combined and checked against the roof's capacity under BS EN 1990. That is why a light dead load never means the roof is fine: a structure that passes on weight alone can still fail once snow and wind are added in combination.
From a weight figure to a signed answer
Free structural pre-check
An indicative screening from a few roof details. Shows whether the load picture looks comfortable, tight, or needs a closer look. No cost, no commitment.
Desktop roof loading report
A full site-specific assessment to BS EN 1990, combining dead, snow and wind, signed by a qualified structural engineer. From £130 residential, £150 commercial, no VAT added.
Order online
Submit the roof and array details and receive the engineer-signed report within the 48-hour benchmark from confirmed scope.
Solar panel weight and roof load questions
How much do solar panels weigh per square metre?
A rail-mounted, in-plane commercial solar PV array typically adds about 15 to 25 kg/m² (0.15 to 0.25 kN/m²) of dead load over the array footprint: the panels at roughly 11 to 13 kg/m² plus the rails, clamps and fixings. A ballasted flat-roof system is heavier, typically 30 to 60 kg/m² (0.30 to 0.60 kN/m²), because the ballast holds the array down against wind uplift. These are typical, indicative figures; the actual figure depends on the specific system and the manufacturer's datasheet.
How much does a single solar panel weigh?
A typical commercial solar panel weighs around 25 kg, with most modules in the 22 to 35 kg range. A 470 W module is roughly 22 kg; a large-format 650 W module is around 34.6 kg. Most current commercial modules sit between 25 and 30 kg.
How much weight does a ballasted solar system add to a flat roof?
A ballasted flat-roof commercial system typically adds about 30 to 60 kg/m² (0.30 to 0.60 kN/m²) of dead load over the array footprint. Higher-tilt, more exposed or heavier configurations rise to around 75 to 100 kg/m² (0.75 to 1.0 kN/m²), because the ballast quantity is set by the wind uplift calculation under BRE Digest 489. The added load concentrates over the array footprint, not the whole roof.
What is the dead load of solar panels?
Dead load is the permanent self-weight a solar PV system adds to the roof: the panels, the mounting frame and, on flat roofs, the ballast. For rail-mounted arrays it is typically 0.15 to 0.25 kN/m² (15 to 25 kg/m²) over the array footprint; for ballasted flat-roof systems it is typically 0.30 to 0.60 kN/m². Dead load is assessed under BS EN 1991-1-1 and is one of three load inputs, alongside snow and wind.
Is the kg/m² figure enough to know if my roof can take solar panels?
No. Dead load in kg/m² is only one of three inputs. It is combined with snow load, which varies by site and altitude, and with wind uplift, then checked against the roof's capacity under BS EN 1990. A roof that looks light enough on dead load alone can still fail once snow and wind are added. Whether a specific roof can carry a specific array requires a project-specific structural assessment.
Can my roof take solar panels?
That cannot be answered from a weight figure alone. It depends on the existing roof structure and its condition, the proposed array, the mounting and ballast, and the site's snow and wind loads, all assessed together under the Eurocodes. Our free structural pre-check gives an indicative screening, and a Desktop Structural Roof Loading Report, signed by a qualified structural engineer, gives the definitive answer.
Have the array weight? The next question is whether the roof can carry it.