Start with electricity units
Use monthly kWh, not only the rupee bill. Fixed charges and tariff slabs distort a price-only comparison. Mark seasonal peaks and planned loads such as air-conditioning, pumps, EV charging or an additional floor.
Estimate useful generation
Expected yield depends on location, orientation, tilt, shading, temperature and system losses. Ask for annual generation with assumptions and a month-wise range—not a single universal ‘units per day’ promise.
Check how much generation you can use
Daytime consumption has high immediate value. Export treatment depends on the applicable utility arrangement. A larger plant may make sense for high consumption, but oversizing purely to maximise export can weaken returns.
Treat subsidy as a financing input
Central household assistance reaches its standard ceiling at 3 kW. A 5 kW plant can still be right for a larger load; a 3 kW plant can be too large for a low-consumption home. Decide capacity first, then calculate assistance.
Ask for three scenarios
Compare a conservative, expected and high-consumption case. Each should show gross cost, assistance, expected annual generation, self-consumption, export assumption, residual bill and loan repayment.
Official references
Regulations, eligibility and utility procedures can change. Verify the current rule and site-specific approval before investment.