Solar System Size Calculator
Find the right solar system size for your home based on your consumption, city, and roof space
Frequently Asked Questions
Sizing a solar system in Pakistan means matching system capacity to actual electricity consumption and local solar irradiance — a system sized for Karachi's sun exposure won't perform identically if installed in Lahore or a northern city with different average sunlight hours, and system type (on-grid, off-grid, or hybrid) changes what "properly sized" even means.
Why city and system type both change the right answer
Solar irradiance — the amount of usable sunlight energy a location receives — varies meaningfully across Pakistani cities, so the same monthly electricity consumption requires a different-sized system depending on where it's installed; a location with lower average irradiance needs proportionally more panel capacity to generate the same monthly units as a sunnier location. System type matters just as much: an on-grid system is sized primarily against consumption and target offset percentage (what portion of the bill you want solar to cover), with no battery backup consideration since the grid absorbs excess and covers shortfalls. An off-grid or hybrid system additionally needs to account for backup hours desired and essential load during an outage, since without grid backup, battery capacity has to be sized to actually carry the specified critical loads through the specified outage duration — this is a fundamentally different sizing question from simply offsetting a bill.
A worked example
The same monthly electricity consumption figure produces a different recommended system size for an on-grid setup (sized purely to offset consumption) versus a hybrid setup requiring several hours of backup for essential loads (which needs additional battery capacity on top of the generation capacity) — treating both system types as needing "the same size system" ignores that off-grid and hybrid setups carry a battery-sizing requirement that on-grid systems simply don't have.
How this connects to your other utility planning
The monthly units figure that drives this sizing calculation should come from your actual Electricity Bill Calculator history rather than a rough guess, since under- or over-stating consumption directly under- or over-sizes the recommended system. Once a system is sized, the Solar Payback Calculator estimates how long it takes to recover the installation cost through bill savings under current net billing regulations.
Common mistakes
Sizing a solar system against a single month's consumption (especially a low-usage month like a mild spring month) rather than looking at consumption across a full year — including high-usage summer months when air conditioning drives units up substantially — is the most common mistake, and it results in a system that's undersized for the months that actually matter most for cost savings.