The right system size depends on two things: how much electricity you use and how much shade-free roof you have. Here is the quick method our engineers start with.
Step 1: Find your monthly units
Look at your electricity bill for the number of units (kWh) you use in a month. If you only have the bill amount, divide it by your tariff per unit. For example, a ₹6,000 bill at ₹8 per unit is about 750 units a month.
Step 2: Convert units to kilowatts
In most of India, 1 kW of rooftop solar generates roughly 4 units a day, or about 120 units a month. Divide your monthly units by 120 to get the system size. In our example, 750 ÷ 120 ≈ 6 kW.
Step 3: Check your roof
Each kW needs roughly 80 sq ft of shade-free roof. A 6 kW system therefore needs about 480 sq ft. If your roof is smaller, you can install a smaller system, use higher-efficiency panels, or add a carport or ground-mount section.
What changes the answer
- Shade from trees, tanks or nearby buildings reduces generation.
- Roof type — RCC, tin shed and curved roofs need different mounting.
- Future load such as an EV or air-conditioning may justify a larger system now.
- Net-metering limits set by your electricity distribution company.
For a quick estimate, try our solar savings calculator. For an exact design, request a free site survey.