How to Choose the Right Solar System Size for Your Home
Use your electricity bill to work out whether you need 1, 2, 3 or 5 kW, and how much roof space it takes.
In this article
The right system size depends on how many units you use, not on how big your house is. Here is a quick way to work it out.
Step 1: Find your monthly units
Look at the last 6–12 electricity bills and note the units (kWh) consumed. Take the average. Summer months are usually higher because of fans and ACs.
Step 2: Divide by 120
In West Bengal, 1 kW of panels produces about 4 units a day, or roughly 120 units a month. So:
- Up to 120 units/month → 1 kW
- About 240 units/month → 2 kW
- About 360 units/month → 3 kW
- About 600 units/month → 5 kW
Step 3: Check your roof
You need about 100 sq ft of shadow-free roof per kW. Water tanks, trees and neighbouring buildings can cast shadows, which is why we always do a site visit.
Step 4: Think about the subsidy
The PM Surya Ghar subsidy reaches its maximum of ₹78,000 at 3 kW. For many families, 3 kW is the sweet spot between cost and savings.
Try the solar calculator on our home page for a quick estimate, then book a free site visit for an exact design.