Case Studies
How a 50kW Rooftop Solar Plant Transformed a commercial space with green energy and Future
This case study examines the strategic installation of a 50kW on-grid rooftop solar power plant who Facing high operational overheads from steep commercial electricity bills under the TANGEDCO LM51 tariff, the Ownership sought a solution to reduce costs and champion environmental stewardship.
The 50 kW solar plant, which generates approximately 74,825 units annually, was perfectly sized to match the Commercial space daytime consumption. This resulted in an immediate reduction of the monthly electricity bill over 75% savings. With a net investment of ₹22,50,000, the project is on track for a rapid payback period of just 5 years and 8 months, proving to be a resounding financial and educational success.
Client: Private workspace," a private Co-working space, Tamil Nadu.
Tariff Category: TANGEDCO LM51, a commercial tariff, which has significantly higher rates than residential tariffs.
The Challenge: High & Unpredictable Operational Costs
The Co-working campus runs extensive facilities during peak sunlight hours (8:00 AM to 4:00 PM), including:
• Multiple Conference halls with AC and lighting. • Dining and party hall.
• Water pumps. This heavy daytime load resulted in substantial electricity bills that were a major drain on the Ownership budget.
Energy Profile Before Solar:
• Average Monthly Consumption: 6,589 units (kWh)
• Blended Tariff Rate LM51: Approx. ₹13.00 per unit (inclusive of energy, demand, and f ixed charges)
• Average Monthly Bill: 6,589 units × ₹13.00/unit = ₹85,657
• Annual Electricity Cost: ₹85,657 × 12 months = ₹10,27,884
The management needed a solution that would provide long-term protection against TANGEDCO's annual tariff hikes and free up capital for educational development.
A 50kW on-grid rooftop solar system was engineered and installed. The system operates under Tamil Nadu's "Net Feed-in" policy for commercial consumers.
System Specifications:
• Plant Capacity: 50 kWp
• System Type: On-Grid (Net-Feed-in)
• Location: Chennai, Tamil Nadu
• Annual Generation (Year 1): 74,825 units (kWh)
The "Self-Consumption" Strategy:
Under the Net-Feed in policy, it is most profitable to consume the solar power as it is generated ("self-consumption"). This is because the value of self-consumed power is equal to the high retail tariff (₹10.45/unit), whereas any excess power exported to the grid is Claimed at the cost of ₹3.37 at a much lower feed-in tariff.
The 50kW system was sized perfectly. Its average monthly generation (6,236 units) is just below the Workspace average consumption (6,589 units), ensuring that nearly 90% of the solar power generated is self-consumed on-site, maximizing the financial benefits.
The impact of the solar installation was immediate and transformative.
Before vs. After: A Monthly Cost Comparison (Year 1)
This table tracks the payback on the ₹3,00,000 investment, with no subsidy
Payback Analysis:
As the table shows, the remaining investment of ₹6,47,269 at the start of Year 4 is fully recovered early in that year.
• Payback Calculation: (₹6,47,269/ ₹8,35,216.9) × 12 months = 9.2 months.
• Total Payback Period: 3 Years and 9 Months.
1. Financial Prudence: The Workspace converted a recurring liability (electricity bill) into an income-generating asset.
2. Operational Resilience: The workspace is protected from annual 4-5% tariff hikes, making its long-term budget planning stable and predictable.
By generating 74,825 units of clean electricity in its first year, the co-working space has significantly reduced its carbon footprint.
• Annual CO2 Reduction: 50 kW × 650 kg CO2/kW/ year = 32,500 kg (32.5 tons) of CO2 emissions avoided.
The 50kW solar project at Chennai workspace is a landmark success. It underscores that for Co working spaces, solar power is not an expense but a critical, high-return investment. By achieving a payback in under 3.75 years.
