Solar Roof Area Calculator

Check whether your roof has room for solar. This solar panel area calculator works out the shadow-free space a system needs in sq. ft., or flips it around to show how many kW and panels fit in the roof space you have.

Plan 80 to 100 sq. ft. of shadow-free roof per kW, including row spacing and walkways:

System	Roof area needed
1 kW	80 – 100 sq. ft.
2 kW	160 – 200 sq. ft.
3 kW	240 – 300 sq. ft.
5 kW	400 – 500 sq. ft.
10 kW	800 – 1,000 sq. ft.

Calculate Roof Area for Solar

I want to know

System size (kW) Not sure what size you need? Start with the solar system size calculator.

Your Roof Estimate

–

shadow-free area needed

In square metres–

Panels (540 – 620W)–

Planning norm80 – 100 sq. ft. per kW

Measure before you buy: usable space shrinks around tanks, parapets and shade. A site visit by a local solar contractor will confirm what really fits and today's price.

Built and maintained by Solar Calculators Pro · How we convert roof area into kW

Roof Area Needed for Solar Panels by System Size

System Size	Roof Area (sq. ft.)	Roof Area (sq. m.)	Panels (550W)
1 kW	80 – 100	8 – 9	2
2 kW	160 – 200	15 – 19	4
3 kW	240 – 300	22 – 28	6
5 kW	400 – 500	37 – 46	10
10 kW	800 – 1,000	74 – 93	19

The 80 to 100 sq. ft. per kW norm includes row spacing and maintenance walkways, not just panel surface. A single 550W panel is about 21 sq. ft. of glass, but tilted rows need gaps so they do not shade each other.

How Many Solar Panels Can Fit on My Roof?

Divide your usable, shadow-free roof area by 80 to 100 sq. ft. per kW. Common roof sizes:

Usable roof area	System that fits	Panels (550 W)
200 sq. ft.	2 – 2.5 kW	4 – 5
300 sq. ft.	3 – 3.5 kW	6 – 7
500 sq. ft.	5 – 6 kW	10 – 11
1,000 sq. ft.	10 – 12 kW	19 – 22

Higher-wattage 600 to 620 W panels fit slightly more kW in the same space. Measure only the area that stays free of shade from 9 am to 4 pm.

What Counts as Usable Roof Space

Shadow-free window: the area should get direct sun from roughly 9 am to 3 pm year-round. Water tanks, parapets, staircase headrooms and nearby buildings all cast moving shadows.
Orientation: south-facing exposure generates the most in India. East and west work at a small loss; pure north-facing pitched roofs are usually skipped. Get the exact angle from the solar panel tilt angle calculator.
Structure: flat RCC roofs take standard ballasted or anchored structures. Metal and tile roofs need rail systems, which change spacing slightly.
High-rise flats: shared roofs need society consent; per-flat entitlement is often limited to 1 to 2 kW of the common roof.

Measuring Your Roof the Right Way

The number you enter should be usable area, and finding it takes ten minutes:

Measure the full slab first (length × width in feet, or trace it in a satellite map app), then subtract the water tank footprint, staircase headroom, parapet shadows and anything permanent.
Watch the shadows at three times: around 9 am, noon and 3 pm. Any area shaded in two of the three checks should be excluded; a winter check matters most because shadows are longest.
Neighbouring buildings count. A taller building to the south is the most damaging neighbour a solar roof can have; the strip it shades in December is effectively dead area.
Pitched roofs: only the south, east and west faces are usable; enter the area of those faces, not the plan area of the house.

What Fits a 350 sq. ft. Terrace in Surat

A Surat homeowner clears the tank and shaded corners and is left with 350 sq. ft. of clean terrace. In "what fits my roof" mode, the calculator returns 3.5 to 4 kW: up to 7 or 8 modern panels. At Surat's 5.0 sun hours that supports roughly 420 to 480 units a month of generation, enough for a mid-size home. If the family needed 5 kW, the honest answer is that this roof cannot host it with proper spacing, and 620W panels or an elevated structure over the tank area become the options to discuss.

After the Area Check: Design Decisions That Follow

Tight fit? Go high-wattage. 620W panels extract about 15% more capacity from the same area than 540W ones; specify this in the quote request.
Elevated structures reclaim area. Raising panels 6+ feet clears tanks and creates usable space below, at ₹3,000 to ₹8,000 per kW extra; often the cheapest way to fit the next kilowatt.
Set the tilt before the layout. Row spacing depends on tilt; get your angle from the tilt angle calculator so the layout drawing uses real numbers.
Then size the system properly: roof capacity is the ceiling, not the target. The system size calculator tells you what you actually need.

Roof Planning Slip-Ups

Using the plot or plan area. Balconies, overhangs and pitched faces make plan area misleading; measure the actual installable surface.
Ignoring future construction. A planned first-floor room or neighbour's third floor can shade tomorrow what is sunny today; site the array away from that edge.
Packing panels edge to edge. Skipping walkways saves area on paper and makes every future cleaning and repair a rope-access job.
Trusting one noon-time look. Noon shadows are the shortest of the day; an area that passes at noon may still lose two morning hours to next door's tank.

How Roof Space Is Estimated

Area needed = System kW × 80 to 100 sq. ft.
Max system = Roof area ÷ 100 (conservative) to Roof area ÷ 80 (tight fit)

Space allowances

Norm: 80 – 100 shadow-free sq. ft. per kW, standard Indian rooftop planning
Includes: inter-row spacing and walkways for flat-roof tilted mounting
Conversion: 1 sq. m. = 10.76 sq. ft.

Roof Space Questions

How much roof area is required for a 3kW solar system?+

About 240 to 300 sq. ft. (22 to 28 sq. m.) of shadow-free roof. That covers 6 panels of 550W plus the row spacing and walkways a tilted flat-roof installation needs.

How many solar panels fit on a 1000 sq ft roof?+

If the full 1,000 sq. ft. is shadow-free, roughly a 10 to 12 kW system fits, which is 19 to 22 panels of 550W. In practice tanks and shading usually reduce the usable area, so 7 to 9 kW is more typical on such roofs.

Can solar panels be installed on a small 200 sq ft roof?+

Yes. 200 sq. ft. of shadow-free space takes about 2 to 2.5 kW, enough to offset 220 to 300 units a month. Using 620W panels squeezes the most capacity out of a small roof.

Why do panels need more space than their own area?+

On flat roofs, panels are tilted toward the sun, so each row casts a shadow behind it. Rows must be spaced so the winter sun clears the row in front, and walkways are needed for cleaning, roughly doubling the raw panel footprint.

Does the roof direction matter?+

Yes. In India panels should face true south for maximum annual output. East or west facing loses about 10 to 15%; the tilt angle calculator gives the ideal tilt and direction for your city.

Is my roof strong enough for solar panels?+

A solar array loads only about 15 to 20 kg per sq. m., well within the capacity of a sound RCC roof. Old, cracked or lightweight sheet roofs should be assessed by the installer; ballasted structures avoid drilling where waterproofing matters.

How much roof area does a 5kW solar system need?+

Plan 400 to 500 sq. ft. of shadow-free area, which carries 9 to 10 panels of 550W with row spacing and walkways. With 620W panels a tight but workable 5 kW fits in about 400 sq. ft.

Can panels go over my water tank or on a raised structure?+

Yes. Elevated structures 6 feet or higher routinely span tanks and create shaded utility space below. They add ₹3,000 to ₹8,000 per kW and need proper wind-load engineering, but they are the standard fix for cluttered Indian terraces.

How do I calculate roof area for solar panels?+

Multiply the system size in kW by 80 to 100 sq. ft. to get the roof area needed, or divide your usable shadow-free roof area by 80 to 100 to find how many kW fit. Leave out water tanks, stair rooms and anything that casts shade.

What does rooftop solar cost per square foot of roof?+

Roughly ₹580 to ₹725 per sq. ft. of roof used for an on-grid system before subsidy, because each kW costs about ₹58,000 and needs 80 to 100 sq. ft. Price your exact system with the solar panel cost calculator.