How much do solar panels weigh on a roof?

A typical solar panel weighs 18–22kg and covers about 1.7m². Including the mounting system, expect 14–18 kg/m² for on-roof systems. This is comparable to heavy concrete roof tiles.

Can my roof support solar panels?

Most UK roofs built after 1960 can support solar panels without structural modifications. Standard 150mm rafters at 400mm centres can typically carry an additional 15–20 kg/m² beyond existing tile weight. Older roofs or those with 100mm rafters may need assessment.

What is wind uplift for solar panels?

Solar panels act as sails and can experience significant wind uplift forces. In exposed or coastal areas (Wind Zone 3), uplift forces can exceed 1.2 kPa. Mounting systems must be designed to resist these forces.

Do I need a structural survey for solar panels?

Most MCS-certified installers include a basic structural assessment. A full structural engineer’s report is recommended if: your roof is pre-1960, the rafters are under 100mm, or you’re in a high wind zone.

What is the difference between on-roof and in-roof solar?

On-roof (rail-mounted) panels sit above your existing tiles on brackets. In-roof (integrated) panels replace the tiles and sit flush. In-roof is lighter but more expensive. Flat roof ballast systems use weights to hold panels in place without penetrating the membrane.

TradeCalculator

Solar Roof Loading Calculator — Weight, Rafter Capacity & Wind Uplift

Check if your roof structure can support solar panels. Calculates panel weight plus mount system per m\u00b2 against rafter size and spacing capacity.

Number of Panels

Total solar panels planned

Panel Weight

Weight per panel (typical: 20kg)

Panel Area

Area per panel (typical: 1.7m\u00b2)

Mount Type

Mounting system affects weight

Rafter Spacing

Wind Zone

Price Per Panel (optional)

How We Calculate This

This calculator determines the total loading from solar panels and mounting systems, then compares it against your rafter capacity.

The formula

Total weight = (Panels × Panel weight) + (Array area × Mount weight/m\u00b2)

Load per m\u00b2 = Total weight ÷ Array area

Combined load = Existing roof load + Solar load

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.