How many solar panels fit on my roof?

Far more than you need. Across the 525 cities we have measured, the median roof could physically hold about 69 panels — while a typical home only needs 15 to 22. Roof capacity is rarely the limit. Shading, orientation and how much electricity you actually use are.

The number nobody publishes

"How many panels fit" and "how many panels do I need" get treated as the same question. They are not, and the gap between them is enormous. Using Google's aerial imagery across 525 cities, the median rooftop measures about 213 m² and could take roughly 69 panels. The median home needs closer to 17.

The arithmetic

A standard 400W residential panel is roughly 1.87 m × 1.13 m — about 2.1 m² (22.5 sq ft) each. So in theory:

The catch is the word usable. Your total roof area and your usable area are very different numbers.

What eats your usable area

• Fire code setbacks. The one people never expect. Most jurisdictions require clear pathways — commonly 3 ft along ridges and sometimes along edges — so firefighters can move. On a small or complex roof this can remove a third of the surface before anything else.
• Obstructions. Plumbing vents, chimneys, skylights, dormers, satellite dishes. Each needs clearance, not just its own footprint.
• Wrong-facing planes. In the northern hemisphere a north-facing slope produces 30-50% less and is rarely worth using. Orientation compared →
• Shading. Area that is shaded for much of the day is area you should not fill. This is usually the real constraint, and the hardest to judge from the ground. How to assess it →

Worked example

A 1,600 sq ft roof (about 149 m²) with two slopes:

1. North-facing slope unusable → 75 m² left
2. Fire setbacks take roughly 25% → 56 m² left
3. Two vents and a chimney with clearance, about 8 m² → 48 m² left
4. 48 ÷ 2.1 ≈ 22 panels, roughly 8.8 kW

Total roof 149 m²; usable 48 m². Most of a roof is not panel space, which is why estimating from floor area or a satellite screenshot goes wrong.

Capacity by city

Measured median roof size and panel capacity, from Google's imagery:

The right-hand column is the one that matters. Filling the left-hand column costs far more and returns less, because you cannot save money on electricity you were never going to buy. Why exports pay so little →

Getting your actual number

Estimating from floor plans or eyeballing a satellite photo will not account for setbacks, obstructions or shading. Enter your address and we read your specific building from Google's aerial and 3D imagery — usable area, panel count and measured sunlight hours after shading, for your roof rather than an average one.

What this looks like in real cities

Measured rooftop data, spanning the range from fastest to slowest payback we have found:

See all 525 cities →

Frequently asked

Related guides

Check your own roof free →

General information, updated 2026-08-22. Not financial, tax or engineering advice.