Rooftop Solar Calculator

Enter your open, shade-free roof area. The calculator sizes an on-grid (grid-tie) rooftop system, lists the equipment, prices it item by item and estimates how much electricity it makes and what that saves on your bill.

Capacity = roof area ÷ 100, rounded down to whole kWp (70 % of the roof is usable, and each kWp needs 70 sq ft). Monthly generation = kWp × 91.65 kWh. Monthly savings = generation × your grid tariff (for educational / health establishments: × the grid tariff minus the solar tariff). Payback = system cost ÷ monthly savings.

• Institution or company. Standard tariff. You buy the system; the tool shows payback.
• Educational institution / health establishment. Supplier model: a supplier installs the system and sells you the power at a fixed solar tariff, so the cost is shown for reference and the result is a bill reduction.
• Commercial (shop, office, factory). Same equipment and cost rules; savings use the tariff you enter (default ৳12.21, an assumption).
• Personal (home). Same rules; savings use the tariff you enter (default ৳8, an assumption). Home tariffs are slab-based, so use the average rate from your bill.

Prices as of October 2026, excluding VAT and taxes. These are this calculator's own planning assumptions; real prices vary by supplier.

• It is a planning estimate, not a design or a quotation. No shading, tilt, orientation or structural study is done; real output and quantities depend on the site.
• Prices and tariffs change. VAT, taxes and financing costs are not included.
• On-grid systems need net-metering approval from your electricity distributor before connection.

This is an independent planning tool by Rasel Rana. The calculation may contain errors and is provided as is, without warranty. Check every figure with a licensed solar installer and your electricity distributor before making a decision.