Solar Load & System Cost Calculator
Formula Reference
Daily Energy Need (kWh) = Σ (Appliance Watts × Quantity × Hours/day) ÷ 1000Required Panel Capacity (kW) = Daily Energy ÷ (Peak Sun Hours × Derating Factor)
Inverter Size (kW) = Total Connected Load (kW) × 1.25 safety margin
Battery Capacity (kWh) = (Daily Energy × Days of Autonomy) ÷ (Depth of Discharge × Round-trip Efficiency)
Typical Appliance Wattages (2026, Inverter-Type)
| Inverter AC (1.5 ton) | ~1,200 W |
| Inverter Refrigerator | ~120 W |
| LED Bulb | ~10 W |
| Ceiling Fan | ~75 W |
| Washing Machine | ~500 W |
| Water Pump/Motor | ~750 W |
Methodology, interpretation & sources
Purpose. Estimates required solar panel, inverter, and battery capacity from your appliance load, then calculates total installed system cost — for houses and buildings in Pakistan.
How to use the result. Start with source data you can verify, enter values on a consistent unit and time basis, and record the assumptions used. The main inputs on this page include Peak Sun Hours (PSH) Pakistan average: 4.5–6.5 hrs/day. Karachi ~5.5, Faisalabad summer ~6.5., System Derating Factor (%) Accounts for inverter/wiring losses, dust, temperature. Typical: 75–80%., Backup Duration (Days of Autonomy), Depth of Discharge (%) Lithium: ~90%. Lead-acid: ~50%., Your Name, Email. Re-run the calculation when those assumptions change rather than carrying an old result forward.
Decision use. Use this result as a planning and screening aid within a wider risk-management process. The calculator should support, not replace, competent judgement and site-specific verification.
Limitations. Document the assumptions and input source so another person can reproduce the calculation and confirm that the result remains valid when conditions change.
Primary references. Use the current edition/version that applies to your jurisdiction and organization:
Editorial note. Prepared and maintained by Impact Tech Solutions. Editorially updated 28 September 2026. No individual professional credential is claimed on this page; high-consequence, statutory, tax, engineering or health decisions should be independently verified against the current primary source and, where required, a qualified professional.