The installation of solar panels on terrace roofs is on the rise in India. A lot of homeowners are confused as to how to calculate rooftop area for solar panels for their home.
Homeowners are now getting the benefit of the central subsidy under PM Surya Ghar: Muft Bijli Yojana, and they are happily switching to free and cleaner energy.
If you are planning a rooftop solar system but do not know how to work out the area required and the number of solar panels needed, you will know exactly how much rooftop area your home solar plant needs.
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How to Calculate Solar Panel Requirements for Your Home?
Finding the exact solar panel size for your home takes a simple four-step calculation based on your electricity use.
- Go through your last 12 months’ electricity bills and note the units (kWh) consumed each month.
- Add up the total units for the 12 months and divide by 12 to get your average monthly consumption in kWh. This is the starting point for sizing your system.
- Divide your average monthly consumption by the monthly generation of a 1 kW solar system. In India, a 1 kW solar panel system generates about 4 units a day on average (4 to 5 units on a clear sunny day), which is about 120 units a month. This gives you the total solar system capacity you need in kilowatts.
- Divide that capacity by the wattage of one solar panel, usually 550 watts or 600 watts, and round up. This gives you the number of panels needed for your rooftop installation.
For example, Amit’s electricity use over the last 12 months was 450 + 400 + 400 + 400 + 450 + 500 + 550 + 500 + 450 + 400 + 350 + 450 = 5,200 units.
So his average monthly consumption is about 433 units. Dividing 433 by 120 units per kW gives a system size of about 3.6 kW.
With 550-watt panels, Amit needs 7 solar panels for home; with 600-watt panels, he needs 6.
This step-by-step approach gives you the right solar system size, so you get the most savings for your money invested.
Step 1: Find your average monthly consumption
- Divide Amit’s yearly consumption of 5,200 units by 12. We get 433.33 units per month, his average monthly electricity use.
Step 2: Find the size of the solar system in kW
- 1 kW of solar generates about 120 units a month in India.
- To find the system size, divide the average monthly consumption by 120.
- 433.33 ÷ 120 = 3.61 kW.
- So Amit’s house needs a solar system of about 3.6 kW. If your result is close to 3 kW, our guide to a 3 kW solar rooftop for home covers that size in detail.
Step 3: Find the number of solar panels
- Most home solar panels in India today are rated between 550 watts and 600 watts. This rating is the panel’s capacity, printed on its label as Wp (watt peak).
- To calculate solar panel capacity in kW, divide the watts by 1,000: a 550 W panel is 0.55 kW and a 600 W panel is 0.6 kW.
- Now divide the system size by the capacity of one panel:
- 550 W panels: 3.61 ÷ 0.55 = 6.56, rounded up to 7 panels (total 3.85 kW)
- 600 W panels: 3.61 ÷ 0.6 = 6.02, so 6 panels (total 3.6 kW)
- Amit’s house needs a solar plant of about 3.6 to 3.85 kW, made up of 6 to 7 solar panels of 600 W or 550 W each.
Solar Panel Size in Feet
Solar panel size depends on its wattage and cell type. Here are the common sizes of solar panels that you may find on Indian rooftops:
| Panel type | Size in mm | Size in feet | Area per panel |
| Older 330 W to 400 W (72-cell) | about 1956 x 992 | about 6.4 ft x 3.3 ft | about 21 sq ft (1.9 sq m) |
| 550 W to 585 W (144 half-cut cells) | about 2278 x 1134 | about 7.5 ft x 3.7 ft | about 28 sq ft (2.6 sq m) |
| 600 W and above | about 2172 x 1303 or 2382 x 1134 | about 7.1 ft x 4.3 ft or 7.8 ft x 3.7 ft | about 29 to 31 sq ft (2.7 to 2.8 sq m) |
So the 550 watt solar panel size in feet is roughly 7.5 ft long and 3.7 ft wide. For example, JAKSON’s 585 W N-type TOPCon module measures 2278 x 1133 mm. Newer, higher-wattage panels are bigger per panel, but they produce more power per square foot, so you need fewer of them.
How to Calculate the Total Rooftop Area Required for Solar Panels
There are two numbers to know: the space the panels cover, and the total roof area you should set aside.
- Panel footprint. Multiply the area of one panel by the number of panels. For Amit’s seven 550 W panels: 7 x 28 sq ft = about 195 sq ft. This is the bare minimum; panels can’t be packed edge to edge on a flat terrace.
- Total rooftop area required. On a flat Indian terrace, panels are tilted towards the south in rows, so each row needs a gap to avoid shading the row behind it, especially on winter mornings. You also need walkways for cleaning and clearance from the parapet, water tank and staircase head. That is why MNRE advises that a 1 kW rooftop system generally requires about 10 sq m (about 108 sq ft) of shadow-free area. With today’s 550 W and larger panels, 100 sq ft per kW is a good working figure.
Solar panel area per kW formula: Rooftop area required (sq ft) = System size (kW) x 100
So Amit’s 3.6 kW system needs about 360 sq ft of shadow-free rooftop area.
This area should get at least 5 hours of direct sunlight a day, with no shade from trees, nearby buildings or water tanks. A south-facing, open stretch of terrace is ideal. A few hours of shade on even one panel can pull down the output of the whole string.
Solar Panel Area per kW: Quick Reference Table
| System size | Suits a monthly bill of about | No. of 550 W panels | Panel footprint | Rooftop area required |
| 1 kW | 120 units | 2 | about 56 sq ft | about 100 sq ft (10 sq m) |
| 2 kW | 240 units | 4 | about 111 sq ft | about 200 sq ft (20 sq m) |
| 3 kW | 360 units | 6 | about 167 sq ft | about 300 sq ft (30 sq m) |
| 4 kW | 480 units | 8 | about 222 sq ft | about 400 sq ft (40 sq m) |
| 5 kW | 600 units | 10 | about 278 sq ft | about 500 sq ft (50 sq m) |
| 6 kW | 720 units | 11 | about 306 sq ft | about 600 sq ft (60 sq m) |
| 8 kW | 960 units | 15 | about 417 sq ft | about 800 sq ft (80 sq m) |
| 10 kW | 1,200 units | 19 | about 528 sq ft | about 1,000 sq ft (100 sq m) |
Area required for 3kW solar panel in square feet: the most popular home size needs about 300 sq ft of shadow-free roof, with six 550 W panels. A 3 kW system also gets the full central subsidy of up to ₹78,000 under PM Surya Ghar.
Area required for 5kW solar panel in square feet: about 500 sq ft, for homes using 550 to 650 units a month. See our 5 kW solar system price guide for cost and savings.
Before You Finalise: Check Your Terrace
- Shade: stand on your terrace at 9 am, 12 noon and 3 pm and note where shadows fall. Only count the area that stays sunny.
- Direction: a south-facing space gives the best output in India. East and west work too, with slightly lower generation.
- Height from roof: on a standard tilted structure, the lower edge of the panel usually sits about 6 inches to 12 inches above the slab. If you want to keep using your terrace, an elevated structure raises the panels to about 6 to 8 ft, so the space underneath stays usable.
- Roof strength: a 550 W panel weighs about 28 to 32 kg. An RCC roof in good condition carries a home system easily. It is recommended to get the cracks on the roof or leakage from the roof fixed before installation.
- Approvals: on-grid systems need net metering approval from your DISCOM, and the PM Surya Ghar subsidy needs a registered vendor.
Put your numbers into our rooftop solar calculator for a quick estimate based on your own bill.
Frequently Asked Questions
Q1. How much area is required for a 1 kW solar panel system?
About 100 sq ft (roughly 10 sq m) of shadow-free roof. Two 550 W panels cover about 56 sq ft of that; the rest allows for spacing and access.
Q2. How much area is required for a 3 kW solar system in square feet?
About 300 sq ft. That is enough for six 550 W panels in tilted rows with walkways. If your terrace is tight, a layout with fewer rows or an elevated structure can sometimes fit it in less.
How much area is required for a 5 kW solar panel system?
About 500 sq ft, or around 50 sq m, for ten 550 W panels.
What is the official roof area per kW for rooftop solar in India?
MNRE’s consumer guidance says a 1 kW rooftop system generally requires about 10 sq m of shadow-free area. The actual figure can vary with today’s higher-wattage panels.
What is the size of one solar panel in feet?
A 550 W panel is about 7.5 ft x 3.7 ft, or about 28 sq ft. Older 330 W to 400 W panels were about 6.4 ft x 3.3 ft.
How many units does a 550-watt solar panel produce?
About 2.2 units a day on average (0.55 kW x 4 units), or around 60 to 70 units a month, depending on your location, season and shade.
How high are solar panels above the roof?
On a standard structure, the lower edge sits about 6 inches to 12 inches above the roof. Elevated structures usually raise it to about 6 to 8 ft so the terrace can still be used.
How many solar panels do I need for 400 units per month?
400 ÷ 120 = about 3.3 kW. Six 550 W panels (3.3 kW) cover that, on about 330 sq ft of roof. For 500 units a month, plan for about 4.2 kW: eight 550 W panels and about 420 sq ft.
How much area do I need for a 50 kW or 500 kW rooftop plant?
The same rule of about 10 sq m per kW applies as a starting point, so 50 kW needs about 500 sq m and 500 kW about 5,000 sq m. On metal-sheet factory roofs, panels often follow the roof slope, which can reduce this. See our rooftop solar for factories page for more information.
What if my roof is smaller than the area I need?
Install the largest system your shadow-free area allows. Even a 2 kW system can cut a large part of your bill. Higher-wattage panels and elevated structures can also help you fit more on a small terrace.
With government subsidies and trusted solar manufacturers like JAKSON Solar, solar panels for houses are now more affordable than ever. Once you know your rooftop area for solar panels, the next step is a site survey, where our team confirms the layout, shade and exact system size for your home.
For more information: Call JAKSON Solar Experts at: 1800-103-2600 (Toll Free) OR Email at: solar-bu@jakson.com
