Commercial Solar Sizing — California

Divide the bill by the tariff to get monthly kWh, then divide by your region's per-kW monthly yield (≈110–135 kWh/kW in sunny India). A ₹4,000 bill at ₹8/unit (500 kWh) typically needs 3.5–4.5 kW — seven to nine 550 W panels. This calculator does exactly that math with local values.

Modern 540–580 W panels occupy ~2.6 m² each; with walkways and spacing, budget 80–100 sq ft (7.5–9.5 m²) per kW for flat roofs. A typical 3 kW home system needs roughly 250–300 sq ft of shade-free area.

Usually 80–95%. Net-metering rules may cap capacity at your sanctioned load, slabs mean your last units are the cheapest to leave on the grid in some states, and consumption varies seasonally. Oversizing into low-value exports rarely pays — check your state's settlement rules.

Solar scales: leave inverter headroom (DC/AC ratio up to 1.3) or wall space for a second string. EV purchases and new ACs typically add 100–400 kWh/month — if those are planned within two years, size for them now; module additions later cost more per watt than doing it once.