Solar Panel Calculator
Calculate panels needed, system cost, monthly generation, and payback period for a solar setup.
Construction
Solar Panel Calculator
Generated on April 24, 2026
Your Energy Requirement
Tip: "Connection size" refers to your peak AC load. Typical Pakistani homes run 3–10 kW; commercial setups 15+ kW.
Solar Panel Selection
Panel Pricing
Market rate in Pakistan (2024): typically PKR 45–65/watt for Tier-1 panels.
Location, Savings & InstallationOptional
Pakistan avg: 5. Karachi/Lahore ~5.2; Multan ~5.5; Islamabad ~4.8.
Inverter + structure + wiring + labor. Typically 35–50% of panel cost.
Pakistan 2024 residential slab rates: ~PKR 20–60/unit depending on consumption. Commercial ~PKR 40–55.
Panels Needed
15 panels
585 W each · 8,775 W installed · 8.78 kW
Daily Gen
37.3 kWh
Monthly Gen
1,135 kWh
Annual Gen
13,622 kWh
System Cost
PKR 675,675
Monthly Savings
PKR 56,761
Annual Savings
PKR 681,077
Payback Period
1.0 years
Oversized for losses: 8,235 W of panels installed for your 7,000 W target (system type Grid-tied — ~85% efficiency).
Payback Timeline
Cumulative savings (green) crosses system cost (red dashed) at the payback point. Everything above the red line after that is pure profit.
Monthly Generation (seasonal)
Estimated monthly output accounting for seasonal sun variation in Pakistan. Summer months generate ~20% more than winter.
Cost Breakdown
10-Year Value
Most quality panels are warrantied for 25 years of output. After payback, everything is profit. Rising electricity tariffs make real savings even higher.
Step-by-step calculation
Formula
Panels = Ceil(System W ÷ Efficiency ÷ Panel W). Daily Gen = Installed kW × Sun Hours × Efficiency. Payback = Total Cost ÷ Annual Savings.
- 1Target system size: 7 kW = 7,000 W AC output
- 2System type: Grid-tied (no battery) → overall efficiency 85%
- 3Required panel capacity = 7,000 ÷ 0.85 = 8,235 W DC
- 4Chosen panel: 585 W each
- 5Panels needed = ⌈8,235 ÷ 585⌉ = 15 panels
- 6Total installed = 15 × 585 = 8,775 W (8.78 kW)
- 7━ Generation ━
- 8Daily kWh = 8.78 × 5 hrs × 0.85 = 37.29 kWh
- 9Monthly ≈ 37.29 × 30.44 = 1,135 kWh
- 10Annual ≈ 37.29 × 365.25 = 13,622 kWh
- 11━ Cost ━
- 12Panel cost = 8,775 W × PKR 55 = PKR 482,625
- 13Installation overhead (40%) = PKR 193,050
- 14Total system cost = PKR 675,675
- 15━ Savings & Payback ━
- 16Monthly savings = 1,135 kWh × PKR 50/kWh = PKR 56,761
- 17Annual savings = PKR 681,077
- 18Payback period = PKR 675,675 ÷ PKR 681,077/yr = 1.0 years
?What is the Solar Panel Calculator?
A solar panel calculator helps you size and cost a photovoltaic system for your home or business. Enter your power requirement (e.g. a 5 kW, 7 kW, or 10 kW connection), pick a panel wattage from common market sizes (585W, 555W, 545W and others), and the calculator tells you exactly how many panels you need, total installed wattage, expected daily/monthly/annual electricity generation, full system cost (including inverter and installation), and how long until the system pays for itself through reduced electricity bills. It is especially valuable in Pakistan and South Asia where rising unit tariffs and reliable sunshine have made solar a strong investment. The tool accounts for real-world losses — inverter inefficiency, cabling losses, dust, shading, and temperature derating — so the recommended panel count is realistic rather than theoretical.
The Formula
Panel capacity is over-provisioned so the AC output still matches your target connection after system losses. The 'efficiency' factor (~85% grid-tied, ~78% hybrid, ~72% off-grid) bundles inverter efficiency, cable losses, dust/soiling, and temperature derating. 'Peak sun hours' is the equivalent number of hours per day at standard 1000 W/m² irradiance — roughly 5 hours average across Pakistan, ranging from 4.8 in Islamabad to 5.5 in Multan. Monthly generation multiplies daily by 30.44 (average calendar month); annual by 365.25 to include leap days. Payback is the simple undiscounted period — real payback is faster because electricity tariffs tend to rise over time.
Practical Examples
A typical Pakistani home with a 7 kW connection using 585W panels needs 15 panels (8,775 W total), generates ~35 kWh/day, costs around PKR 1,400,000–1,500,000 all-in, saves ~PKR 52,500/month at PKR 50/kWh, and pays back in ~2.3 years.
A 10 kW commercial setup using 555W panels needs 22 panels (12,210 W), generates ~50 kWh/day, and typically costs PKR 2.0–2.2 million including inverter and installation.
A small 3 kW home system using 450W panels needs 8 panels (3,600 W) and generates ~14 kWh/day — enough to offset most daytime consumption in a small household.
Switching from 450W to 585W panels for the same 7 kW system reduces panel count from 20 to 15 — fewer roof-mount points, shorter wiring runs, and typically lower total cost despite higher per-panel price.
A commercial 50 kW rooftop setup using 620W panels needs ~95 panels, generates ~250 kWh/day, and for a factory with PKR 55/kWh tariff saves ~PKR 420,000/month — payback in under 2 years with good net-metering.
Post-NEPRA 2024 tariff rises, payback periods for most residential solar setups in Pakistan have shortened from 4–5 years to 2–3 years — earlier adopters locked in even better economics.