The right system size depends on how much electricity you use and how much roof you have. Here is a quick way to estimate it.
Step 1: find your monthly units
Look at your electricity bill for the units (kWh) consumed each month. If you only know the amount, divide it by your tariff per unit as a rough guide.
Step 2: rule of thumb for generation
In good sun, 1 kW of solar produces roughly 4 units a day, or about 120 units a month. Actual output varies with season, shade, tilt and cleaning.
Step 3: divide
System size (kW) ≈ monthly units ÷ 120
Example: a home using about 450 units a month needs about 450 ÷ 120 ≈ 3.75, so a 4 kW system would cover most of its use.
Step 4: check your roof
You need roughly 100 sq ft of shadow-free roof per kW. A 3 kW system needs about 300 sq ft. A south-facing roof with little shade works best, and our team checks shading and orientation on site.
Don’t forget the subsidy
Residential rooftop systems can receive up to ₹78,000 under PM Surya Ghar for systems of 3 kW and above. Read the subsidy guide.
Try the calculator
Our solar and subsidy calculator does the arithmetic for you. For an exact design, request a free site survey.
Want this worked out for your roof?
Book a free site survey. We will size the system and handle the subsidy paperwork.