"Will it fit?" usually comes right after "how much will it make?". The answer depends on the roof as much as the plant, so here is how we think about space on homes, shops and factory sheds.
The rule of thumb
On a flat concrete roof, allow 90 to 100 square feet of shadow-free area for every kW. That covers the panels, the gaps between rows (so one row doesn't shade the next in winter), a path to walk and clean, and clearance from the parapet.
| Plant size | Flat roof area needed |
|---|---|
| 3 kW | 270 – 300 sq ft |
| 5 kW | 450 – 500 sq ft |
| 10 kW | 900 – 1,000 sq ft |
| 25 kW | 2,250 – 2,500 sq ft |
| 50 kW | 4,500 – 5,000 sq ft |
| 100 kW | 9,000 – 10,000 sq ft |
For a sense of scale, a single modern Waaree panel of 600 to 700 watts is roughly 2.4 m long and 1.1 to 1.3 m wide, about 29 to 33 square feet on its own.
Metal sheds need less
On a metal sheet roof the panels usually sit flush, following the slope. There's no need for gaps between rows to avoid shading, so the same plant often fits in 60 to 70 square feet per kW, depending on walkways. The catch is that you're stuck with whichever way the roof faces. An east-west shed loses around 7% of generation compared with a south-facing one, which is usually still well worth doing.
Before anything goes on a shed we check the sheets, purlins and fixings. A tired roof should be repaired before the panels go on, not after.
What eats into usable space
- Water tanks and stair rooms, plus the shadows they throw, which are longest in December.
- Parapet walls. A tall parapet shades the first row on winter mornings and evenings.
- Trees and taller buildings, especially to the south.
- Space you need for other things: drying clothes, a terrace garden, the floor you might add one day.
When an elevated structure helps
On crowded terraces we often raise the panels on a taller steel structure. Lifting them clear of the parapet and the tank shadows recovers a surprising amount of area, and the space underneath stays usable. We recently worked on a roof of about 4,500 square feet where the owner wanted a plant that would normally need 6,300 square feet or more. An elevated structure made it fit.
Space and size aren't the same question
A roof that can take 20 kW doesn't mean you should put 20 kW on it. Under West Bengal net metering, units you don't use within the year lapse on 1 April, and a plant can't exceed your sanctioned load anyway. We size to consumption first and then check the roof. If the roof is too small, we look at higher-wattage panels or an elevated structure before suggesting a smaller plant. Our guide to sizing a home plant walks through it.
Get your roof measured
Our free survey measures the roof, maps the shade and gives you a 3D layout showing exactly where each panel goes. Book one here, or send a few photos of the roof on WhatsApp for a first opinion.
Quick answers
How much space is needed for a 5 kW solar system?
About 450 to 500 square feet of shadow-free flat roof, or less on a metal shed where the panels can sit flush.
How much roof area is needed for a 100 kW solar plant?
Around 9,000 to 10,000 square feet on a flat roof, and usually less on a large metal shed.
Can solar panels be installed on a tin shed?
Yes. Panels are fixed on rails along the sheet roof after the sheets, purlins and fixings have been checked.