Free Tool

Solar System Size Calculator

Enter your monthly electricity bill or units consumed. Get the exact system size (kW), number of panels, and rooftop area you need — for free.

A ₹5,000 monthly electricity bill (250–350 units) typically needs a 2.5–3 kW system — 5–6 panels and about 150–180 sq ft of roof.

Updated August 2026 Reviewed by the SolarOps360 Engineering Team

Enter Your Details

All fields are used only to estimate your system size. Results are indicative.

Example: 300 kWh/month needs a 2.4 kW system — 5 panels of 545W, about 123 sqft of roof, generating around 3,614 kWh/year. Enter your own bill or usage above.

Showing an example — enter your details above for your own numbers.

2.4
System Size (kW)
5
Panels Needed
123
Roof Area (sqft)
3,614
Annual Gen. (kWh)

Estimates assume ~5.5 peak sun hours/day and 75% system efficiency. Actual output varies by location, shading, and equipment. Bill-to-units conversion uses an indicative state average tariff.

How It Works

How This Calculator Works

  1. 1

    Enter your monthly electricity bill

    Type your average monthly electricity bill amount in ₹, or switch to enter the number of units (kWh) consumed monthly.

  2. 2

    Select your state

    Choose your state from the dropdown. The calculator uses state-specific electricity tariff rates to determine your consumption accurately.

  3. 3

    Choose your system type

    Select on-grid (most common, no batteries), off-grid (batteries, no grid), or hybrid (batteries + grid). This affects the system sizing.

  4. 4

    Click Calculate

    Hit the Calculate button to instantly see your recommended system size in kW, number of solar panels needed, rooftop area required, and annual generation estimate.

  5. 5

    Get your full report

    Click "Email Me My Full Report" to receive a detailed PDF with complete system specifications, equipment list, and next steps — delivered to your inbox.

Definitions

Understanding Your Results

System Size (kW)
The total capacity of solar panels needed, in kilowatts, to offset your electricity consumption.
Panels Needed
The number of individual solar panels required at your selected panel wattage to reach the recommended system size.
Roof Area
Approximate shadow-free rooftop area needed, including mounting clearance and row spacing between panels.
Annual Generation
Estimated electricity your system will generate per year, based on average peak sun hours and typical system losses.
FAQs

Frequently Asked Questions

How many solar panels do I need for a ₹5,000 monthly electricity bill?
A ₹5,000 monthly electricity bill typically represents 250–350 units (kWh) at an average tariff of ₹7/unit. This requires a 2.5–3 kW solar system with 5–6 panels of 545W each, occupying approximately 150–180 sqft of rooftop space.
What is the formula to calculate solar system size?
Solar system size (kW) = Monthly units (kWh) ÷ (Peak sun hours per day × 30 days × 0.75 efficiency). For most Indian locations, peak sun hours are 5–5.5 hours/day. So 300 units ÷ (5.5 × 30 × 0.75) = approximately 2.4 kW.
How much rooftop area is needed for a 1 kW solar system?
A 1 kW solar system using 545W panels needs 2 panels, each requiring approximately 25 sqft including mounting clearance. Total: around 50–60 sqft per kW of installed capacity.
What is the difference between on-grid, off-grid, and hybrid solar systems?
On-grid systems are connected to the electricity grid, allow net metering (sell excess power), and have no batteries. Off-grid systems use battery storage and are independent of the grid — ideal for remote areas. Hybrid systems have both grid connection and battery backup, giving the best of both.
How much electricity does a 3 kW solar system generate per month in India?
A 3 kW solar system in India generates approximately 360–400 kWh per month, assuming 4–5 peak sun hours per day and accounting for 20–25% system losses. This varies by location — Rajasthan generates more than West Bengal due to higher solar irradiance.

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