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Solar Suite

Solar Panel Size & Rooftop Area Calculator

Calculate recommended kW solar capacity, area required, and number of panels based on daily power usage.

Live 2026 Data
Monthly Units 100 - 1500+ kWh
Area Required 100 - 1000 sq ft
Panels Needed Mono-PERC / Bifacial
Recommended Size 1 kW to 10+ kW

1. Enter Configuration Parameters

Frequently Asked Questions (FAQ)

How much shadow-free rooftop area is needed per kW of solar?

Typically, 1 kW of solar installation requires about 90 to 100 square feet of shadow-free, south-facing rooftop area.

What is the cash subsidy for rooftop solar under PM Surya Ghar Yojana?

The central government provides a direct subsidy of Rs. 30,000 per kW for the first 2 kW of solar capacity, and Rs. 18,000 for the 3rd kW. The maximum subsidy is capped at Rs. 78,000 for any residential installation of 3 kW or higher.

How much roof space is required to install a 3 kW solar system?

A 3 kW residential solar system requires approximately 250 to 300 square feet of shadow-free rooftop space. Each solar panel is roughly 20 square feet, and a 3 kW setup typically uses 6 to 8 high-efficiency monocrystalline panels.

How many units of electricity does a 1 kW solar panel generate daily?

In India, a 1 kW solar plant generates an average of 4 to 4.5 kWh (units) of electricity per day in standard sunny conditions. This translates to roughly 120 to 135 units per month, or 1,500 units annually per kW of installed capacity.

What is solar net-metering, and how does it work?

Net-metering uses a bidirectional meter to record both the power you import from the grid and the excess solar power you export to the grid. At the end of the billing cycle, your DISCOM bills you only for the net units consumed (Import minus Export).

What is the typical ROI payback period for residential solar in India?

With the PM Surya Ghar subsidy, the net out-of-pocket cost for a 3 kW solar system is roughly Rs. 70,000 to Rs. 90,000. Generating Rs. 30,000 worth of free power annually, the system pays for itself in 2.5 to 3 years, followed by 22+ years of free power.

Does a grid-tied solar system work during power outages?

No. Standard grid-tied solar systems automatically shut down during a power cut for safety reasons (anti-islanding) to protect utility workers repairing the lines. To run appliances during power outages, you need a hybrid solar system with battery backup.

About This Calculator

Target Audience: Property owners exploring solar ROI, panel sizing & government subsidy benefits

What Does This Calculator Do?

This calculator determines the rooftop solar plant size (kW) and number of solar panels required to offset your electricity bill or support specific heavy appliances (like ACs).

How to Use It

  1. Target Bill Reduction: Select the percentage of your bill you want to offset (e.g., 100%).
  2. Rooftop Area: Enter the shadow-free rooftop area available in square feet.
  3. Panel Rating: Select panel wattage (e.g. 400W or 540W Mono PERC).

The Logic Explained Simply

  • The Concept: Rooftop space and average daily solar generation determine your system size. In India, a 1 kW solar system requires about 80-100 square feet of area and generates ~4 units of electricity daily.
  • The Formula:
  • Required Plant Size (kW) = Monthly Units / 120 (since 1 kW makes ~120 units/month)
  • Number of Panels = Plant Size (Watts) / Panel Rating (Watts)

Real-World Calculation Breakdown

If your monthly electricity bill shows consumption of 360 units:

  1. Required Plant Size: 360 units / 120 units per kW = 3 kW solar plant.
  2. Number of 540W Panels: 3,000 Watts / 540 Watts = 5.55 -> 6 panels.
  3. Rooftop Space Required: 6 panels × 20 sq ft/panel = 120 sq ft of shadow-free rooftop space.

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