Your result
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Enter your values, then click Calculate result.How this calculator helps
Plan a solar system from your average monthly electricity usage. The tool estimates system capacity, panel count, monthly production and a simple payback period using editable Pakistan-focused assumptions.
How to Size a Solar System in Pakistan
Calculate solar kW, panel count, inverter capacity and realistic generation from your own electricity use.
Read the complete guide →How to use it
- 1
Use the average of several recent electricity bills instead of one unusual month.
- 2
Enter realistic peak-sun-hours for your location and the panel wattage you plan to buy.
- 3
Use the capacity and panel count as a starting point for a professional site survey.
Formula and methodology
Daily units = monthly units ÷ 30. Required kW = daily units ÷ (peak-sun-hours × system efficiency).
Uses editable energy demand, sunlight, equipment and loss assumptions. It is a planning model rather than a site survey or electrical design.
Worked calculation example
A home consuming 600 units monthly uses about 20 units daily. At 5.2 peak-sun-hours and 80% efficiency, it needs roughly a 4.8 kW array before practical rounding.
How to interpret your result
Treat the calculated kW as an energy-based starting point; roof layout, daytime load and inverter limits decide the installable system.
Input guide
Use a 12-month average rather than one unusually hot month.
Peak-sun-hours should reflect the city and seasonal conditions.
Panel wattage must match the actual model being quoted.
Scenario comparison
| Scenario | What it demonstrates |
|---|---|
| 300 monthly units | typically represents a smaller home and modest array. |
| 600 monthly units | useful for checking a mid-sized residential design. |
| 1,200 monthly units | requires closer review of roof area, sanctioned load and export rules. |
Common mistakes to avoid
- Sizing only from the rupee value of the bill.
- Assuming nameplate output is produced all day.
- Ignoring shade, temperature, dust and conversion losses.
Ask the installer for a site-specific generation simulation, string layout and protection schedule before purchasing.
What can affect the result?
Shade and orientation
Trees, buildings, roof direction and tilt directly affect daily production.
Seasonal demand
Summer cooling loads may require a larger system than the annual average suggests.
System losses
Temperature, dust, wiring and inverter losses reduce output from nameplate capacity.
Limits of this estimate
The estimate does not model an hourly load profile, roof geometry, export limits, battery storage or site-specific solar irradiance.
Sources and review information
Frequently asked questions
Is the solar system calculator free?＋
Yes. SolvePilot tools are free, work in your browser, and require no account.
Does SolvePilot store my values?＋
No. Calculations run locally in your browser and the values you enter are not sent to a server.
Should I treat the result as an exact bill or quotation?＋
No. Results are informed estimates. Final charges can vary because of taxes, tariffs, lender terms, usage patterns, or provider rules.
How can I improve the accuracy?＋
Use recent values from your own bill, statement or institution, review every assumption, and confirm important results with the relevant official source.
Does it include batteries?＋
The initial result sizes panels. Battery capacity depends on the backup load and required backup hours and should be calculated separately.