Estimate the rooftop solar capacity your property may need using your electricity consumption, location, available roof space, and electricity tariff. Explore estimated generation, installation cost, savings, applicable subsidies, and payback.
Follow 6 guided steps to calculate system kW, rooftop panel count, net costs, and payback.
Solar irradiance (Peak Sun Hours) and DISCOM net-metering tariffs vary significantly across Indian states.
Calculated feasibility summary based on your energy consumption baseline and local solar yield.
Seasonal simulation comparing solar output against expected grid electricity consumption across all 12 calendar months.
Solar engineering project costs consist of five key functional subsystems. Below is the transparent engineering Bill of Materials (BoM) cost allocation based on prevailing Indian market benchmark turnkey rates.
| Subsystem / Component | Engineering Specifications & Standards | Share (%) | Estimated Cost (₹) |
|---|---|---|---|
| Solar PV Modules | 550Wp Tier-1 Mono PERC / TOPCon, Half-Cut, DCR Compliant (ALMM listed) | 50% | ₹1,18,800 |
| Solar Inverter | Grid-tied String Inverter, MPPT tracking, IP65 rated, Wi-Fi telemetry monitoring | 18% | ₹42,768 |
| Module Mounting Structure (MMS) | Hot-Dip Galvanized (HDG) / Anodized Aluminum, rated for 150 km/h wind velocity | 12% | ₹28,512 |
| Balance of System (BoS) & Cabling | Solar DC cables (XLPO, UV resistant), AC cables, ACDB/DCDB boxes, SPDs, chemical earthing | 10% | ₹23,760 |
| Installation, Net-Metering & Liaison | Civil footing, electrical cabling, DISCOM net-meter documentation, CEIG approval | 10% | ₹23,760 |
| Total Turnkey Project Cost (Gross) | 100% | ₹2,37,600 | |
| Applicable PM Surya Ghar Central Financial Assistance (Subsidy) | CFA | - ₹78,000 | |
| Net Payable Capital Investment | Net | ₹1,59,600 | |
Launched by the Prime Minister in February 2024 with a ₹75,021 Crore national outlay, the PM Surya Ghar scheme provides direct Central Financial Assistance (CFA) deposited into the consumer's bank account following DISCOM net-meter inspection.
Solar panels are guaranteed by Tier-1 manufacturers for 25 years with a linear power warranty. Below is the multi-year cash flow forecast accounting for 0.7% annual module degradation, 3% grid electricity tariff inflation, routine O&M, and a scheduled inverter replacement in Year 12.
| Milestone Year | Annual Output (kWh) | Yearly Savings (₹) | O&M Maintenance (₹) | Major Component Outlay | Cumulative Net Cash Flow (₹) |
|---|
Our solar sizing model translates your monthly utility bills into an actionable, engineer-verified solar blueprint in 5 logical steps.
Select your Indian State & City to retrieve verified solar irradiance indices (PSH) and regional DISCOM tariff schedules.
Provide your average monthly units (kWh) or bill amount (₹) to compute daily kilowatt-hour generation targets.
Specify usable shadow-free terrace space or calculate it using our built-in length × width setback helper.
Select residential, commercial, or industrial to apply appropriate PM Surya Ghar subsidies or corporate tax depreciation.
Explore recommended system capacity in kW, module count, turnkey capital outlay, annual savings, and payback period.
At the Indian Institute of Solar Energy (IISE), our calculator implements transparent Photovoltaic (PV) system sizing algorithms conforming to Bureau of Indian Standards (BIS) and MNRE best practices.
Determines the daily target kilowatt-hours to offset:
Sizes solar array using local Peak Sun Hours (PSH) and Performance Ratio (PR):
Calculates panel count using 550Wp modules (rounded up):
Sums expected annual kilowatt-hours over 365 operating days:
Models 80% self-consumption + 20% grid export under net metering:
Computes years required to recover net out-of-pocket investment:
To ensure complete academic and technical honesty, all calculation constants and physical modeling assumptions are published below.
| Simulation Parameter | Standard Engineering Value | Technical Rationale & Verification Source |
|---|---|---|
| Peak Sun Hours (PSH) | 4.4 to 5.5 kWh/m²/day | Derived from IMD (India Meteorological Department) and NASA SSE satellite insolation datasets for Indian geographic coordinates. |
| Performance Ratio (PR) | 75.0% (0.75) | Standard temperature coefficient losses (-0.35%/°C above 25°C STC), string inverter conversion efficiency (97.5%), dust/soiling derating (3%), and AC/DC Ohmic cable drop (2%). |
| PV Module Wattage | 550 Wp Tier-1 Mono PERC | Standard utility-grade bifacial/monofacial half-cut cells. Area per module: ~2.27 m² (~24.5 sq. ft.). |
| Roof Area Density Factor | 80 to 85 sq. ft. per kW | Encompasses panel footprint plus mandatory row-to-row inter-panel inter-shading spacing and 600 mm maintenance access pathways. |
| Self-Consumption Share | 80% Direct / 20% Export | Reflects typical daytime occupancy profiles in residential and commercial buildings under standard net-metering regimes. |
| Grid Export Valuation | ₹3.00 to ₹3.50 / kWh | Banking and export energy settlement cap defined by state SERCs (Average Power Purchase Cost - APPC or flat feed-in credit). |
| Module Degradation | 0.7% per annum | Warranty backed linear degradation (first year: 2% initial LID, subsequent years: 0.55%–0.7% annually). |
| Tariff Inflation Rate | 3.0% per annum | Historical 10-year compound annual growth rate of retail electricity tariffs approved by State Electricity Regulatory Commissions. |
Explore benchmark reference scenarios across small homes, medium residences, large villas, commercial offices, and industrial sheds.
| Property Scenario | Monthly Bill | Monthly Units | Recommended System | Panel Count | Roof Space | Net Cost (After Subsidy) | Payback Period |
|---|---|---|---|---|---|---|---|
| Small Residential (1-2 BHK Apartment / Small House) | ₹1,500 / mo | ~200 kWh | 1.65 kW | 3 × 550W | ~140 sq. ft. | ₹52,800 (₹49.5k subsidy) | 3.2 Years |
| Medium Residential (2-3 BHK Independent House) | ₹3,500 / mo | ~460 kWh | 3.3 kW | 6 × 550W | ~280 sq. ft. | ₹1,00,200 (₹78k subsidy) | 3.1 Years |
| Large Residential (4-5 BHK Villa with Multiple ACs) | ₹7,500 / mo | ~1,000 kWh | 6.6 kW | 12 × 550W | ~560 sq. ft. | ₹2,78,400 (₹78k subsidy) | 3.6 Years |
| Commercial Office (Small SME / Branch Facility) | ₹35,000 / mo | ~3,500 kWh | 25.0 kW | 46 × 550W | ~2,125 sq. ft. | ₹12,00,000 (40% AD Tax) | 3.8 Years |
| Industrial Shed (Manufacturing / Warehouse) | ₹1,20,000 / mo | ~15,000 kWh | 100.0 kW | 182 × 550W | ~8,500 sq. ft. | ₹45,00,000 (40% AD Tax) | 3.3 Years |
Depending on your billing structure, roof type, and state jurisdiction, sizing considerations adjust to optimize economic returns.
Residential homeowners benefit from PM Surya Ghar: Muft Bijli Yojana subsidies up to ₹78,000. Typical home installations range from 2 kW to 5 kW, slashing monthly electricity bills by 80% to 95%.
Entering your monthly bill in Rupees allows instant sizing estimation. Our engine subtracts standard fixed meter charges (~5%) and applies your state's active retail tariff slab to derive true energy consumption.
Unit input is the preferred engineering methodology. Directly using kilowatt-hours bypasses municipal taxes, electricity duties, and power factor surcharges, giving 100% mathematical sizing precision.
Commercial tariffs in India often exceed ₹10–₹12 per unit. While direct PM Surya Ghar capital subsidy is ₹0, commercial entities recover up to 40% of project capex through Accelerated Depreciation tax write-offs.
In Maharashtra, MSEDCL, Tata Power, and Adani Electricity implement net-metering regulations with average peak insolation of 5.0 PSH. High residential tariffs (~₹7.80–₹11.50) provide rapid payback in 3.1 to 3.8 years.
Hybrid systems incorporate Lithium-ion (LiFePO4) storage for power cut autonomy. Battery storage adds approximately ₹15,000–₹22,000 per kWh. Sizing requires critical daytime vs nighttime load analysis.
Unlike commercial vendor calculators built to generate sales leads by exaggerating generation claims or quoting artificially low turnkey costs, the Indian Institute of Solar Energy provides an objective, faculty-verified engineering tool.
A web calculator is an essential preliminary feasibility tool, but it cannot replace professional on-site engineering due diligence. Always commission an on-site survey before finalizing contracts:
Verified calculators and design tools developed by IISE faculty for engineers and consumers.
Advanced feasibility tool for residential and commercial rooftop PV sizing with detailed loss derating factors.
Comprehensive technical manual for sizing standalone solar inverters, MPPT controllers, and battery banks.
Explore solar cable voltage drop estimators, solar panel quantity calculators, and PM Surya Ghar subsidy trackers.
Master industry-standard solar software used by EPC firms and utility project developers worldwide.
Industry-standard bankable solar PV energy yield simulation, 3D shading scenes, and loss tree analysis.
Rapid CAD-based commercial rooftop layout modeling, electrical stringing, and bankable reporting.
Architectural 3D solar modeling, shadow trajectory animations, and structural layout blueprints.
Comprehensive practical program covering hands-on rooftop mounting, inverter wiring, and DISCOM net metering.
Use your preliminary calculation as a starting point. Request an engineering review of system capacity, roof shading, project economics, and PM Surya Ghar subsidy approval from IISE technical specialists.
Comprehensive engineering answers prepared by IISE solar faculty.
Whether you are an Indian property owner evaluating rooftop solar feasibility or an aspiring engineer looking to design bankable PV projects, IISE provides the technical foundation you need.
1. Ministry of New and Renewable Energy (MNRE), Government of India – PM Surya Ghar: Muft Bijli Yojana Operational Guidelines (2024–2026).
2. National Portal for Rooftop Solar (pmsuryaghar.gov.in).
3. India Meteorological Department (IMD) & NASA Surface Meteorology and Solar Energy (SSE) Irradiance Database.
4. State Electricity Regulatory Commissions (MERC, GERC, RERC, KERC, TNERC, DERC, UPERC) Tariff Orders and Net-Metering Regulations (2025–2026).
Information Verification Date: Scheme criteria, benchmark turnkey costing, and central subsidies last verified by IISE engineering faculty in October 2026.