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Bijli Hisab Methodology

How electricity usage, solar sizing, generation, savings, and payback are estimated—and where the model should not replace official advice.

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Methodology reviewed 13 June 2026.

Electricity usage

Monthly units are preferred. If only a bill amount is available, the calculator derives a rough unit estimate from an effective rate assumption.

Solar system size

Estimated monthly units are converted into a practical system-size band, then adjusted through generation and roof-loss assumptions.

Solar generation

The public calculator uses a Pakistan-average monthly yield per kW and applies a roof or shading loss. A site survey is required for final design.

Savings and payback

Savings combine estimated daytime self-consumption and exported units, then retain an allowance for residual grid and fixed charges.

Equipment prices

System prices are market ranges, not vendor quotations. Brand, model, protections, structure, installation scope, and battery design can materially change cost.

Source Policy

Official sources are used for tariff and policy context. Reference datasets support solar-generation assumptions. Equipment prices remain market estimates until verified quotations are available.

Official sourceReviewed 13 June 2026

Electricity tariff

Consumer-end tariff assumptions should be maintained from NEPRA and Government notifications. Exact DISCO-level tariffs can be added later as an advanced mode.

NEPRA consumer-end applicable tariff
Official sourceReviewed 13 June 2026

Solar export credit

Solar export assumptions should follow current NEPRA prosumer/net metering or net billing rules for Pakistan.

NEPRA Prosumer Regulations
Reference datasetReviewed 13 June 2026

Solar generation

The public calculator uses a Pakistan average generation assumption so users are not blocked by city/provider selection. Advanced regional tuning can be added later.

Global Solar Atlas
Market estimateReviewed 13 June 2026

Equipment prices

Panel, inverter, mounting, wiring, and installation prices are market estimates until vendor quotations are collected and verified.

Solar panel market price reference

Known Limitations

Provider-specific billing details can differ.
Weather and roof orientation affect solar output.
Daytime usage strongly affects savings.
Installer quotations determine final equipment cost.