Nithyam SoftwareCustomers ask one question first: "How big a system do I need?" Here is a quick method your whole sales team can use, and explain, in under a minute.
Step 1: Find the monthly units
Take the units from the last 6–12 bills and work out the average. If only the amount is known, divide it by the average tariff (for many homes, ₹6–9 per unit including charges).
Example: average bill ₹3,500 at about ₹7 per unit ≈ 500 units a month.
Step 2: Yearly need
Monthly units × 12.
500 × 12 = 6,000 units a year.
Step 3: Units one kW makes in your area
A well-placed 1 kW system in India makes roughly 1,300–1,600 units a year, depending on the state and the weather. Sunny, dry states (Rajasthan, Gujarat) are at the high end; the North-East and hilly areas at the low end. For Telangana and Andhra Pradesh, 1,450–1,500 is a fair planning number.
Adjust for the roof: south-facing or flat roofs with tilted panels get the full figure; east- or west-facing roofs lose roughly 10–12%.
Step 4: Divide
Yearly need ÷ units per kW, rounded up to the next half kW.
6,000 ÷ 1,500 = 4 → recommend 4 kW.
Step 5: Check the limits
- Roof area: plan about 70–100 sq ft of shadow-free roof per kW (more with walkways or elevated structures). 4 kW needs roughly 300–400 sq ft.
- Sanctioned load: many DISCOMs cap net-metered solar at the sanctioned load. If the customer's load is 3 kW, either propose 3 kW or apply for load enhancement first.
- Budget and subsidy: for homes, the central subsidy under PM Surya Ghar is highest up to 3 kW. Show both options when the numbers are close.
Step 6: Show the payback, not just the price
Customers buy savings. For every proposal, show:
- Monthly units generated and the new expected bill
- The subsidy and the net cost after subsidy
- Payback in years and 25-year savings
- An EMI if they will take a solar loan
Keep it honest: say these are estimates, and that actual generation depends on weather, shade and cleaning.
Do it in one tap
Nithyam's solar proposal works this out from the bill: recommended kW, generation, PM Surya Ghar subsidy, net cost, payback, 25-year savings and EMI. It prints them on the quotation PDF with your roof layout. You can change every assumption.