Solar calculator Pakistan: size, panels and cost

Solar calculator Pakistan: from electricity units to a system estimate

Estimate solar panels, system size, roof space, battery backup and indicative cost from your electricity use. For an existing home, start with monthly units (kWh), ideally from twelve months of bills. A rupee bill can include taxes, adjustments, fixed charges and arrears, so bill-to-units conversion is a rough starting point.

How to estimate solar system size

Daily energy is monthly kWh divided by the days in the billing period. A first sizing check is daily energy divided by peak-sun hours and the system performance factor. Choose the city and review shade, orientation, heat and equipment losses before accepting the recommendation. Peak-sun hours describe energy availability, not the length of the day.

Worked example: 700 units a month in Islamabad

At 700 kWh over 30 days, 100% energy coverage, 4.9 peak-sun hours, 18% system loss and no additional shade reduction, the raw requirement is about 5.81 kW DC. The calculator rounds its recommendation up to 6.0 kW before selecting whole panels. With 585 W modules it therefore selects 11 panels, totalling 6,435 W DC (displayed as 6.43 kW by the tool). Ten such panels total 5.85 kW but fall below that rounded recommendation. These are software planning assumptions, not measured Islamabad generation or a production promise.

3 kW, 5 kW and 10 kW: panel count depends on panel wattage

Divide target DC watts by the selected panel wattage and round up. With illustrative 585 W modules, a target of 3 kW needs 6 panels (3.51 kW actual), 5 kW needs 9 (5.265 kW actual), and 10 kW needs 18 (10.53 kW actual). These are arithmetic checks; panel count alone does not establish string compatibility or roof fit.

Solar sizing method and editable assumptions

For the units method, the tool uses a 30-day planning month. Daily target energy is monthly kWh ÷ 30 × coverage percentage. Raw array size is that daily target ÷ (peak-sun hours × 0.82 × shade factor). The tool rounds up to the next 0.5 kW, then rounds panel count up to a whole panel. This is why a simple panel-wattage division can differ from the calculator result.

The shade factors are 1.00 without a selected reduction, 0.95 for low, 0.85 for medium and 0.70 for high shade. City sun-hour defaults and these losses are software planning assumptions; they are not a site-specific solar survey or a direct live import from Global Solar Atlas. Advanced inputs allow a custom sun-hours assumption. Use site evidence for roof orientation, obstructions and seasonal output.

How much battery backup do you need?

A 1,000 W essential load for four hours needs 4 kWh of usable load energy before additional real-world losses. At 90% depth of discharge, that is about 4.44 kWh nominal energy. The calculator then selects whole battery modules using the chosen model's usable-energy figure. Check inverter efficiency, temperature, battery power limits and motor-starting demand separately; an energy figure alone does not prove the equipment can run the load.

Solar prices and electricity rates: use your own quotation

Panel, inverter and battery reference prices are editable planning inputs, not a live dealer feed. Import and export rates are scenario inputs, not confirmation of your tariff or export eligibility. Match them to your current electricity bill, applicable agreement and equipment quotation. Keep quote date, exact model, quantity, warranty scope, installation, protection, structure and taxes in the comparison.

See an appliance energy and backup example. For solar resource methodology use Global Solar Atlas methodology; for product dimensions and electrical limits use the selected manufacturer's current datasheet.

Battery backup and solar savings answer different questions

Battery energy depends on essential load in kW multiplied by backup hours, adjusted for usable depth of discharge and conversion losses. Check starting surges and inverter power separately. Estimate savings by valuing electricity used directly and electricity exported separately; total generation is not automatically a reduction of the bill at one retail tariff.

Review all tariff and export-rate assumptions against your current DISCO agreement and bill. Defaults are editable planning inputs, not a statement of your entitlement. Compare on-grid, hybrid and off-grid choices using a dated itemized quote for panels, inverter, battery, structure, protection and installation. Official reference points include NEPRA and the Global Solar Atlas.

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Method explanation updated 29 October 2026. Software assumptions checked against the Pulse Hatch calculator implementation; market quotations and site measurements remain project-specific.

About Pulse Hatch planning tools

Pulse Hatch publishes construction and solar planning tools with editable project inputs and step-by-step guides. Meet Rohail Khalid, civil engineering and GIS professional, or send a correction or project question. Examples explain assumptions and do not replace a project-specific quotation.