Free · Roof area · Solar capacity
Roof Solar
Area Calculator
Find your roof surface area from house size and pitch — then see how many solar panels fit and how much they produce.
Roof area m²
Panels & kWp
Annual production
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Your house & roof
After north side, chimneys, shading
Your roof
Roof surface area
101.7 m²
footprint 80 m²
Usable area
61 m²
Panels (400 W)
30
System size
12.0 kWp
Estimated annual production
12,252
kWh / year
Estimates assume 400 W panels (~2 m² each), 80% system efficiency and your peak sun hours. Use the solar panel calculator for savings & ROI.
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Pitch adds surface
A steeper roof has more surface area than its footprint. A 30° pitch adds ~15% to the roof area.
Not all roof is usable
Exclude the north side, dormers, chimneys and shaded areas — typically 50–70% of the roof remains usable.
10 m² per kWp
Plan 10–15 m² of clear roof per kWp. A 5 kWp home system needs roughly 50–60 m².
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FAQ
Roof solar FAQ
How do I calculate my roof area?
Multiply the house length by the width to get the footprint, divide by the cosine of the roof pitch to account for the slope, then add overhang. A 10×8 m house with a 30° pitch has a roof of about 10×8/cos(30°) ≈ 92 m² plus overhang.
How many solar panels fit on a typical roof?
A 400 W panel is about 2 m². After excluding the north side, chimneys and shading, a 100 m² roof with 60% usable area fits about 30 panels (12 kWp).
How much roof area do I need for solar?
About 10–15 m² of roof per kWp. A typical 5 kWp system needs roughly 50–60 m² of usable south-facing roof.
Does roof pitch affect solar output?
Pitch affects how much roof surface you have and the optimal tilt. A steeper roof has more surface area but each m² may be less optimally tilted. 30–35° is near-optimal for most northern latitudes.
What is usable roof area?
The fraction of your roof actually suited for panels — typically 50–70% after excluding the north-facing side, dormers, chimneys and shaded areas.
How much does a solar roof produce?
A 5 kWp system on a south-facing roof produces 4,000–7,000 kWh/year depending on your sun hours. Use the panel calculator for precise savings and ROI.
How big is a 400 W solar panel?
About 2 m² (roughly 1.7 × 1.13 m). Higher-wattage panels are slightly larger but produce more per m².
What is the best roof for solar?
South-facing in the northern hemisphere (or north-facing in the south), 20–45° pitch, no shading and at least 10 m² of clear roof per kWp.