Divide your system size (in watts) by your panel wattage. Using 550W panels: a 3KW system needs ~6 panels, 5KW ~9-10 panels, and 10KW ~18 panels. Your system size comes from your monthly units (kWh) and daytime load most Pakistani homes need a 3-10KW system.
The number of panels depends on two things: the system size you need, and the wattage of each panel. Get either wrong and you pay for it too few panels and the grid bill keeps coming; too many and you’re exporting cheap units under net billing. Here’s the full working, the same method Zynergy’s surveyors have applied across 1,000+ projects since 2021.
Step 1 Find Your System Size
Size is set by your monthly units (or bill) and how much load runs during the day. Pull your last three bills ideally including a peak summer month, since June consumption with two inverter ACs running can be double February’s. Find the units consumed, divide by 30 for daily usage, then by 4.5 (Pakistan’s typical units per kW per day) for an indicative system size. The table below maps common household profiles:
| Monthly units | Typical bill profile | Indicative system size |
|---|---|---|
| 300-450 | Lights, fans, fridge, 1 AC part-time | 3KW |
| 500-750 | 1-2 ACs in summer, washing machine, iron | 5-6KW |
| 800-1,100 | 2 ACs, water pump, full family load | 8KW |
| 1,200-1,500 | 3+ ACs or small commercial use | 10KW |
Most homes land between 3KW and 10KW → use the System-Size Calculator or the Load Calculator to refine this against your actual appliances.
Step 2 Divide by Panel Wattage
Number of panels = system watts ÷ panel watts. With 550W panels:
Always round up, never down 5,000W ÷ 550W = 9.1, so fit 10 panels (5.5KW of DC capacity) rather than 9. Installers in Pakistan routinely oversize the array 10-25% above the inverter rating because panels rarely hit their lab-rated wattage on a 65°C Lahore roof. That extra panel costs little and lifts every day’s generation for 25 years.
550W vs 580W Panels: Does Higher Wattage Change the Count?
Higher-wattage 580W panels mean slightly fewer panels and less roof space for the same system size useful when the roof is tight or partly shaded. The panels themselves are nearly identical in physical size; the extra watts come from better cell technology (N-type TOPCon), which also handles Pakistani heat with lower losses. Here’s the practical difference:
| System size | 550W panels | 580W panels | Roof area saved |
|---|---|---|---|
| 5KW | 10 | 9 | ~25 sq ft |
| 8KW | 15 | 14 | ~25 sq ft |
| 10KW | 18 | 17-18 | ~25 sq ft |
The count difference is modest, so don’t pay a heavy premium per watt just to drop one panel. Pay for it where the N-type efficiency and heat performance matter: small roofs, hot cities like Multan and Sukkur, or east-west layouts where every panel must pull its weight.
Step 3 Check Your Roof Area
Each kW needs roughly 80 sq ft. A 5KW system needs ~400 sq ft of unshaded roof; 10KW ~800 sq ft. On a typical RCC lenter roof, panels sit on elevated galvanised structures at a south-facing tilt, which keeps the area usable for walking and water tanks below. On sheet roofs common in workshops and warehouses panels mount flush along the existing slope, so usable area depends on which way the sheets face. Deduct space lost to water tanks, overhead cable shadows, mumty rooms and the parapet’s morning shade before counting. A 120 sq yd (1,080 sq ft) house usually has clear room for 5-6KW; a 240 sq yd roof comfortably hosts 10KW. If your roof can’t fit the panels you need, 580W modules or a ground/elevated structure over the car porch close the gap.
How Many Panels for a Home: Typical Pakistani Setups
If you’d rather start from appliances than bills, here’s how many panels for a home of each common profile. A 5-marla house running a fridge, fans, lights, TV and one 1.5-ton inverter AC draws 18-25 units a day in summer a 5KW system (10 × 550W panels) covers it. A 10-marla home with two 1.5-ton inverter ACs, a water pump and kitchen appliances typically needs 8KW (15 panels). A 1-kanal house with three or more ACs, or any home with a 2-ton unit running through the afternoon, moves to 10KW (18 panels) and a 3-phase connection. Each 1.5-ton inverter AC adds roughly 1.5KW of steady daytime draw budget 3 panels per AC as a quick mental rule.
Solar Panel Calculation: A Worked Lahore Example
Here’s the full solar panel calculation for a real profile. A Johar Town household on LESCO uses 900 units in June (bill ≈ Rs 55,000-60,000 with fuel adjustments) and 450 in January. Daily summer usage: 900 ÷ 30 = 30 units. Required size: 30 ÷ 4.5 ≈ 6.7KW but sizing to the summer peak alone overshoots winter, while sizing to winter leaves summer uncovered. We average toward the high side because summer is when LESCO’s expensive slabs bite: an 8KW system generating ~36 units/day covers June consumption almost fully and exports surplus in spring. Panel count: 8,000W ÷ 550W = 14.5 → 15 panels, needing ~640 sq ft of the family’s 1,800 sq ft roof. The home keeps its 3-phase connection, qualifies for net billing, and installation took 9 days within our standard 7-15 day window.
Number of Panels for 5KW and 10KW: Quick Reference
These two sizes account for most residential quotes in Pakistan, so they deserve precise answers.
Number of panels for 5KW
With 550W modules: 9-10 panels (fit 10 for healthy DC oversizing). With 580W: 9 panels. Roof needed: ~400 sq ft unshaded. Expected generation: 20-25 units/day. Suits homes using 500-750 units a month typically one to two inverter ACs.
Panels for 10KW
With 550W modules: 18 panels; with 580W: 17-18. Roof needed: ~800 sq ft, and a 3-phase connection is required for net billing at this size. Expected generation: 40-50 units/day suits 1,200-1,500 unit homes, small offices and shops with daytime-heavy load.
Don’t Forget Output & Future Load
A panel count that’s right today can be wrong by next summer. Match the count to the output you need now, then add headroom for what’s coming: a new 1.5-ton inverter AC adds ~7-8 units a day (roughly 3 extra panels), an electric water heater or a future EV charger considerably more. Adding panels later is possible but rarely clean your inverter must have spare DC capacity, matching panel models may be discontinued, and net-billing approval is tied to your sanctioned load. Under NEPRA’s 2026 net-billing rules there’s also a ceiling on useful oversizing: exports earn the notified rate, less than what imports cost you, so build for the load you’ll genuinely run in daytime, not the largest array the roof can hold.
Single-Phase or 3-Phase: The Constraint Buyers Miss
Your meter type quietly caps your panel count. Single-phase connections in Pakistan suit systems up to roughly 5KW; anything larger needs a 3-phase connection which most DISCOs also require for net metering approval. If you’re planning 8-10KW on a single-phase meter, the phase upgrade through K-Electric or LESCO should start before the panels are ordered, since it can take longer than the installation itself. Sanctioned load matters too: net-billing capacity is generally tied to it, so a home sanctioned at 5KW can’t register a 10KW system without first upgrading the sanction. Zynergy checks both during the free survey and handles the paperwork it’s a routine part of how 1,000+ projects have gone live without approval surprises.
FAQs
About 9-10 using 550W panels, or 9 with 580W modules. Fit 10 where roof space allows the DC oversizing improves real-world output.
Around 18 × 550W panels on ~800 sq ft of unshaded roof. You’ll also need a 3-phase connection for net billing at this size.
A 1.5-ton inverter AC needs roughly 3 × 550W panels’ worth of capacity to run through the day, on top of your base load. Tonnage and inverter vs non-inverter type change the maths → solar for AC.
Yes 580W panels need fewer units for the same size and save about 25 sq ft per system. The saving is one panel in most residential sizes, so weigh the per-watt price difference.
Around 4-5 × 550W panels (a 2-3KW system). At low consumption, weigh payback carefully fixed costs spread over fewer saved units.
A 550W panel measures roughly 25 sq ft including spacing. Budget ~80 sq ft per kW of system size on an unshaded RCC lenter roof.
Only if your inverter has spare capacity and compatible panels are still available. It’s cheaper to size for known future loads now than to retrofit.
Always units. Rupee amounts swing with fuel price adjustments and slab changes; units measure your actual consumption.
Net-billing system size is generally capped by your sanctioned load a 5KW sanction supports roughly a 5KW system. Upgrading the sanction through your DISCO lifts the cap.
The count formula is identical, but Lahore’s smog-season dip means we sometimes recommend one size up for winter-heavy users, while Karachi homes size closer to the formula.
Reduce the usable area first, then count panels. Shaded strings drag down healthy panels, so a smaller well-placed array beats a bigger compromised one.
Yes the System-Size Calculator converts your units into a recommended size and panel count, and a free Zynergy survey confirms it on-site.
