Solar Panel Payback Calculator India (PM Surya Ghar)

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Formula at a glance

Solar Payback Calculator: Units a year — kW × units per kW a day × 365 × (1 − degradation)^(year − 1). Example: 3 kW home system with subsidy → Payback period: 3.3 years — How the Solar Payback Calculator works: Units a year — kW × units per kW a day × 365 × (1 − degradation)^(year − 1)

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📘 About the Solar Panel Payback Calculator

A rooftop solar system in India produces about 4 units per kW each day — a 3 kW system about 360 units a month, enough for many homes. Under the PM Surya Ghar Muft Bijli Yojana, homes get a central subsidy of ₹30,000 per kW for the first 2 kW and ₹18,000 for the third (up to ₹78,000).

The calculator adds up the bill savings year by year — with your tariff rising and panels slowly losing output — subtracts the cost after subsidy and maintenance, and shows when you break even, the total saving over 25 years, the CO₂ you avoid and the roof space you need.

🧮 Formula

Units a year

kW × units per kW a day × 365 × (1 − degradation)^(year − 1)

Saving

Units used × tariff + units exported × 40% of tariff − maintenance

Payback

First year total savings ≥ cost after subsidy

✏️ Worked examples

3 kW home system with subsidy

You enter
Currency	₹ Indian rupee
System size	3 kW
Total cost before subsidy	180000
Apply PM Surya Ghar subsidy (India, residential)	Yes — ₹30,000/kW up to 2 kW, ₹18,000 for the 3rd kW, max ₹78,000
Other subsidy amount (if 'No')	0
Units per kW per day	4 kWh
Your electricity rate	8 per unit
Tariff rise a year	3%
Share of solar you use yourself	80%
Panel output loss a year	0.5%
Cleaning & maintenance a year	1000

You get
Payback period	3.3 years
Your cost after subsidy	₹1,02,000 (subsidy ₹78,000)
Electricity generated	360 units a month · 4,380 a year
Savings in year 1	₹29,835
Total savings over 25 years	₹10,26,218 (10.26 lakh)
Return on investment	906% over 25 years
CO₂ avoided	74.3 tonnes over 25 years (≈ 3,537 trees growing for a year)
Roof area needed	about 300 sq ft (28 m²) of shade-free roof

Payback 3.3 years.

5 kW at ₹10 a unit

You enter
Currency	₹ Indian rupee
System size	5 kW
Total cost before subsidy	290000
Apply PM Surya Ghar subsidy (India, residential)	Yes — ₹30,000/kW up to 2 kW, ₹18,000 for the 3rd kW, max ₹78,000
Other subsidy amount (if 'No')	0
Units per kW per day	4 kWh
Your electricity rate	10 per unit
Tariff rise a year	3%
Share of solar you use yourself	70%
Panel output loss a year	0.5%
Cleaning & maintenance a year	1500

You get
Payback period	3.5 years
Your cost after subsidy	₹2,12,000 (subsidy ₹78,000)
Electricity generated	600 units a month · 7,300 a year
Savings in year 1	₹58,360
Total savings over 25 years	₹20,03,216 (20.03 lakh)
Return on investment	845% over 25 years
CO₂ avoided	123.8 tonnes over 25 years (≈ 5,896 trees growing for a year)
Roof area needed	about 500 sq ft (47 m²) of shade-free roof

3.5 years.

🧭 How to use this calculator

What you enter

Currency
System size (kW)
Total cost before subsidy
Apply PM Surya Ghar subsidy (India, residential)
Other subsidy amount (if 'No')
Units per kW per day (kWh)3.5–4.5 in most of India.
Your electricity rate (per unit)
Tariff rise a year (%)
Share of solar you use yourself (%)
Panel output loss a year (%)
Cleaning & maintenance a year

What you get

Payback period
Your cost after subsidy
Electricity generated
Savings in year 1
Total savings over 25 years
Return on investment
CO₂ avoided
Roof area needed

💡 Before you install

Apply on the national PM Surya Ghar portal and pick a registered vendor.
Ask for net metering approval from your DISCOM.
Check the roof is shade-free from 9 AM to 4 PM.
Get panel (25-year) and inverter (5–10 year) warranties in writing.

❓ Frequently asked questions

What is the payback period of rooftop solar in India?

Usually 3–6 years with the subsidy, depending on your tariff and how much of the power you use yourself; panels last 25 years or more.

How much does a 3 kW solar system cost?

About ₹1.6–2 lakh for an on-grid system before subsidy; after the ₹78,000 PM Surya Ghar subsidy, about ₹0.9–1.3 lakh.

How much roof area do I need?

About 100 square feet (10 m²) of shade-free roof per kW.

☀️ Solar Panel Payback Calculator (PM Surya Ghar Subsidy)