Step 1: Calculating Monthly Units
At an average blended domestic electricity tariff of approximately ₹6.80 to ₹7.20 per unit in Bihar (including energy charges, fixed charges, and duty), a monthly electricity bill of ₹5,000 corresponds to roughly 680 to 720 units (kWh) consumed per month.
Step 2: Recommended Solar kW Capacity
In Bihar, 1 kW of well-oriented rooftop solar generates approximately 120 to 130 units per month. Therefore:
700 units / 125 units per kW = 5.6 kW
We recommend either a 5 kW or 6 kW on-grid solar system. A 5 kW system will offset ~85-90% of your bill, while a 6 kW system will achieve near 100% net-zero billing annually.
Step 3: Cost, Subsidy & Payback Period
For a 5 kW residential system:
- Turnkey Cost: ~₹2,50,000
- PM Surya Ghar Subsidy: ₹78,000
- Net Customer Investment: ~₹1,72,000
- Annual Savings on ₹5,000 Bill: ~₹55,000 - ₹60,000/year
- Simple Payback Period: ~3.0 Years
Step 4: Roof Area Requirements
A 5 kW to 6 kW system requires roughly 400 to 550 sq. ft. of unshaded rooftop area.