Skip to content
HQ8T

Solar Panel Calculator

Rooftop solar size, cost, subsidy and payback.

units (kWh)

From your bill. Use an average of summer and winter.

hours

4.5–5.5 in most of India.

watts
₹
₹per unit
Solar system size
3 kW
6 panels of 540 W · ~300 sq ft roof
Cost after subsidy
₹1,02,000
₹1,80,000 − ₹78,000 subsidy
Yearly saving
₹28,800
Pays back in ~3.5 years

Generates about 4,271 units a year (356 a month). Subsidy shown is PM Surya Ghar for homes: ₹30,000 per kW for the first 2 kW and ₹18,000 for the 3rd kW (max ₹78,000). Total ₹1.8 Lakh before subsidy.

Estimate only. Get a site survey from an empanelled vendor on the PM Surya Ghar portal; shading, roof direction and panel quality change the output.

How to use

  1. 1Enter the units you use per month from your bill.
  2. 2Check sunshine hours, panel size and cost per kW.
  3. 3Enter your electricity rate per unit.
  4. 4See the system size, cost after subsidy and payback period.

Frequently asked questions

How many kW solar do I need for 300 units a month?

About 2.5–3 kW in most of India, since 1 kW makes roughly 110–130 units a month.

How much subsidy does PM Surya Ghar give?

₹30,000 per kW for the first 2 kW and ₹18,000 for the 3rd kW, up to ₹78,000 for 3 kW or more, for residential rooftops.

How much roof space is needed?

Roughly 100 sq ft of shadow-free roof per kW.

How long does solar take to pay back?

Usually 3–6 years after subsidy, depending on your electricity rate. Panels then keep producing for 25 years.

You may also need