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Solar Calculator & Estimation Tools

Find out what size rooftop solar system suits your home, how many units it can generate and how much PM Surya Ghar subsidy applies, in seconds.

Built-in estimator

Rooftop solar unit & size estimator

Based on the common rule of thumb: 1 kW ≈ 4–5 units per day ≈ 120–150 units per month.

Average monthly electricity use (units / kWh)

Find "units consumed" on your WBSEDCL or CESC bill. Use a 12-month average if you can.

Residential home (eligible for PM Surya Ghar subsidy)

Estimates only. Actual generation depends on sunlight, roof direction and tilt, shading, dust and panel type. No prices are shown; ask us for a written quotation.

Your estimate

Recommended system size—

Units per day—

Units per month—

Units per year—

Shadow-free roof area—

PM Surya Ghar central subsidy—

Subsidy: ₹30,000/kW for the first 2 kW + ₹18,000 for the 3rd kW, maximum ₹78,000. For residential homes using DCR panels, installed through a registered vendor and applied for on pmsuryaghar.gov.in.

Send my estimate to SB TECH

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Advanced calculators from SolarConnect India

Need more detail, such as appliance load, batteries or GST? Use SolarConnect's official tools.

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Size panels from appliance load and rooftop space, check GST and yearly generation.

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Appliance load, rooftop area, subsidy estimate and battery sizing with a printable report.

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Meghna AI Solar Assistant

Ask questions about rooftop solar, subsidy, panels, inverters and batteries.

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How the estimate is calculated

System size = monthly units ÷ 135 (the middle of 120–150 units per kW per month), rounded up to the nearest 0.5 kW.
Generation = system size × 4–5 units per day, or × 120–150 units per month.
Roof area = roughly 80–100 sq ft of shadow-free roof per kW (depends on panel size and layout).
Subsidy = ₹30,000 per kW up to 2 kW, plus ₹18,000 for the 3rd kW, capped at ₹78,000.

For a site-specific answer, read how many units a 1 kW system produces or contact SB TECH for a roof assessment.