📐 How to Size a Solar System for Your Home in Pakistan 2026
5-step guide to calculate exactly how many panels, what inverter and how much battery you need — based on your bills, city sun hours and load-shedding hours. Includes two complete worked examples.
📋 In this guide
- Why Getting System Size Right Matters
- Step 1 — Calculate Your Monthly Consumption
- Step 2 — Find Your City's Peak Sun Hours
- Step 3 — Calculate the Required System Size
- Step 4 — Choose Inverter Type Based on Load-Shedding
- Step 5 — Size Your Battery Storage
- Quick Reference — Right System Size Pakistan 2026
- FAQs
1. Why Getting System Size Right Matters
The most common and costly mistake in Pakistan: buying a solar system based on budget alone rather than actual consumption. An undersized system leaves 30–50% of bills unpaid in summer. An oversized system wastes Rs. 1–3 Lac on excess generation you cannot fully use.
Why target 80–90% coverage instead of 100%? Because net metering credits for excess generation earn at a lower avoided-cost rate than you pay for imports. The 80–90% target maximizes ROI by balancing coverage and cost efficiently.
2. Step 1 — Calculate Your Monthly Consumption
| Season | Typical Monthly Units | Notes |
|---|---|---|
| Peak summer (Jun–Aug) | 700–1,500 units | ACs running 12–18 hrs/day |
| Hot shoulder (Apr–May, Sep) | 400–900 units | ACs starting and stopping |
| Mild (Oct–Nov, Mar) | 200–400 units | Minimal AC |
| Winter (Dec–Feb) | 150–300 units | Heating + lights only |
Annual average: sum all 12 months, divide by 12. Example: 7,200 annual units ÷ 12 = 600 units/month average. This is your sizing baseline.
- No 12 bills? Estimate: 1-ton inverter AC running 8 hrs = ~60 units/day. Add fridge (4 units/day), lights/fans (3 units/day), TV/router (2 units/day) = ~69 units/day. Multiply by 30.
- Planning a new AC or business from home? Add 10–20% for future-proofing.
- Bill in rupees only? Divide by Rs. 35–65/unit depending on your slab to estimate units.
3. Step 2 — Find Your City's Peak Sun Hours
| City / Region | Peak Sun Hours | Monthly kWh per kW Installed | Season Variation |
|---|---|---|---|
| Quetta / Balochistan | 7.0 hrs/day | ~193 kWh/kW/month | Very stable |
| Jacobabad / SEPCO interior | 6.5 hrs/day | ~179 kWh/kW/month | Stable — extreme heat |
| Karachi / Hyderabad | 6.0 hrs/day | ~165 kWh/kW/month | Low variation — coastal |
| Multan / DG Khan / Bahawalpur | 5.5 hrs/day | ~151 kWh/kW/month | Moderate |
| Lahore / Faisalabad / Gujranwala | 5.0 hrs/day | ~138 kWh/kW/month | High — smog cuts winter 35% |
| Islamabad / Rawalpindi / Peshawar | 4.5 hrs/day | ~124 kWh/kW/month | High — fog cuts winter 30% |
Formula: Monthly kWh per kW = Peak sun hours × 30 days × 0.85 (15% system losses). This is the annual average — summer is 30–50% above, winter 30–40% below.
4. Step 3 — Calculate the Required System Size
Formula: System Size (kW) = (Monthly consumption × Coverage target%) ÷ Monthly kWh per kW in your city
Worked Example 1 — Lahore, Rs. 25,000/month bill:
- Monthly consumption: ~550 units (Rs. 25,000 ÷ Rs. 45/unit average)
- Coverage target: 85%
- Solar target: 550 × 85% = 468 kWh/month
- Lahore monthly output: 138 kWh per installed kW
- System size: 468 ÷ 138 = 3.4kW → round up to 5kW
- Why 5kW not 3.5kW? Heat derating 15–25% below STC in summer, panel degradation 0.55%/year, standard inverter sizes.
Worked Example 2 — Multan, Rs. 55,000/month bill:
- Monthly consumption: ~1,100 units (Rs. 55,000 ÷ Rs. 50/unit Multan average)
- Coverage target: 80%
- Solar target: 1,100 × 80% = 880 kWh/month
- Multan monthly output: 151 kWh per installed kW
- System size: 880 ÷ 151 = 5.8kW → round up to 7kW
- Multan note: extreme heat means 20–25% below STC — conservative sizing is essential.
5. Step 4 — Choose Inverter Type Based on Load-Shedding
| Load-Shedding Hours | Inverter Type | Reasoning | Extra Cost |
|---|---|---|---|
| 0–3 hrs/day | On-grid (grid-tied) | Reliable grid — no battery needed | None |
| 3–6 hrs/day | Hybrid (battery-ready) | Get hybrid now, add battery later | Rs. 25,000–45,000 |
| 6–12 hrs/day | Hybrid + battery | Significant shedding — battery saves generator | Rs. 4.2–5.2 Lac |
| 12–18+ hrs/day | Hybrid + large battery + generator | Extreme — generator backup essential | Rs. 6.3–7.8 Lac+ |
- GoodWe ES/EM: best balanced — sub-20ms switching + generator input + SEMS monitoring
- Sungrow SH: premium efficiency but no generator input — for minimal shedding areas only
- Solis RHI / Growatt SPH: budget hybrid with ~30ms switching + generator input
- Huawei SUN2000: premium AI, no generator input, Huawei LUNA2000 battery only
6. Step 5 — Size Your Battery Storage
| Load During Outage | Average Load | 8-Hr Need | Battery Needed | Cost |
|---|---|---|---|---|
| Fans + fridge + lights | ~400W | 3.2 kWh | 1× Pylontech US5000 (3.84kWh) | Rs. 2.1–2.6 Lac |
| 1 AC (1-ton inv.) + basics | ~900W | 7.2 kWh | 2× Pylontech US5000 (7.68kWh) | Rs. 4.2–5.2 Lac |
| 2 ACs + basics | ~1,700W | 13.6 kWh | 3× Pylontech US5000 (11.52kWh) | Rs. 6.3–7.8 Lac |
| 3 ACs + full home | ~2,500W | 20 kWh | 5× Pylontech US5000 (19.2kWh) | Rs. 10.5–13 Lac |
7. Quick Reference — Right System Size Pakistan 2026
| Monthly Bill | Est. Units | System Size | Battery (1 AC, 8hr outage) | On-Grid Cost | Hybrid + Battery |
|---|---|---|---|---|---|
| Rs. 5,000–10,000 | 100–200 | 2–3 kW | 1× US5000 optional | Rs. 2.5–4 Lac | Rs. 5–7 Lac |
| Rs. 10,000–20,000 | 200–400 | 3–5 kW | 1–2× US5000 | Rs. 4–6.5 Lac | Rs. 7–11 Lac |
| Rs. 20,000–40,000 | 400–800 | 5–7 kW | 2× US5000 | Rs. 6–10 Lac | Rs. 11–17 Lac |
| Rs. 40,000–70,000 | 800–1,400 | 7–10 kW | 2–3× US5000 | Rs. 9–14 Lac | Rs. 15–26 Lac |
| Rs. 70,000–1,50,000 | 1,400–3,000 | 10–15 kW | 3–5× US5000 | Rs. 14–22 Lac | Rs. 23–40 Lac |
Lahore benchmarks — other cities 5–20% higher. On-grid excludes battery. Hybrid includes hybrid inverter premium and battery.
Frequently Asked Questions
4-step calculation: (1) Find monthly average consumption from 12 bills. (2) Multiply by 80–85% coverage target. (3) Divide by city monthly output per kW — Lahore 138, Karachi 165, Islamabad 124, Multan 151, Quetta 193 kWh/kW/month. (4) Round up to next standard size (3, 5, 7, 8, 10kW). Example: Lahore, 550 units × 85% = 468 kWh ÷ 138 = 3.4kW → choose 5kW.
80–90% is optimal, not 100%. Oversizing for 100% summer coverage means massive winter excess that earns lower avoided-cost export credits — wasted capital. Fixed charges (meter rent, FAC) always apply regardless of solar — bill can never reach zero. 80–90% target gives fastest payback and best ROI. Exception: very remote areas with unreliable DISCO where 100%+ off-grid security makes sense.
5kW is right if your monthly bill is Rs. 15,000–30,000 (350–650 units). Monthly generation: Lahore ~530 kWh, Karachi ~638 kWh, Islamabad ~478 kWh, Multan ~585 kWh. Bill above Rs. 40,000: consider 7kW. Running 2 ACs simultaneously: 7kW. Running 1 AC: 5kW is right for most Pakistani homes.
10 panels × 550W = 5,500W DC — standard for 5kW with heat buffer. Or 9 panels × 610W N-Type = 5,490W. Roof space: ~30–34m² south-facing unshaded. Always round to 10 panels for 5kW — the extra panel costs Rs. 26,000–35,000 and compensates for Pakistan's 15–25% heat derating below STC ratings.
0–3 hrs load-shedding: on-grid + net metering is fine. 3–6 hrs: hybrid inverter now, add battery later. 6–14 hrs: hybrid + battery — generator savings alone often justify battery in 18–24 months. 14+ hrs: hybrid + large battery + generator input essential. Check actual local hours with neighbours — DISCO averages hide significant area-by-area variation.
Yes, with planning. Panels: most inverters accept more panels up to their DC input limit (GoodWe ES 5kW accepts up to 7,500W DC). Battery: Pylontech is fully modular — start with 1 US5000, add up to 8 units over time. Inverter: cannot upgrade without full system redesign — size inverter for 5-year load forecast. The smartest approach: right-size inverter from day 1, start with 1–2 batteries, expand as budget allows.
Hamesha consumption se decide karein. Agar budget se size karo: Rs. 4 Lac mein 3kW lagwa lo — lekin 600 units monthly consume karte ho to sirf 50% bills cover hoga. Pehle Step 1-3 follow karo, ideal size nikalo (e.g. 5kW), phir budget match karo. Agar budget chota hai: on-grid system lagao aur baad mein battery add karo. Kabhi bhi system chota mat rakho — zinadagi bhar itna hi generation milega.
On-grid systems: Lahore 5kW (Rs. 6 Lac) saving Rs. 23,000/month = ~26 months (~2.2 years). Karachi 5kW (Rs. 7 Lac) saving Rs. 28,000/month = ~25 months. Islamabad 5kW (Rs. 7 Lac) saving Rs. 20,000/month = ~35 months. Hybrid + battery: add 6–12 months payback for battery premium but monthly savings increase Rs. 12,000–20,000 from generator elimination. Best payback: Karachi and Multan due to highest sun hours and electricity costs.
Common Sizing Mistakes Pakistani Buyers Make
- Sizing for current bills only — not future consumption: Adding an AC or moving to a larger home increases consumption. Size for what you'll need in 2–3 years, not just today's bill. Adding 1–2 extra panels now (Rs. 30,000–70,000) is far cheaper than a system upgrade later (Rs. 80,000–1,50,000 in reinstallation alone).
- Ignoring heat derating: A 5kW system doesn't actually produce 5kW in Pakistan's summer heat. Panels operate at 60–80°C — producing 15–25% less than rated. Factor this in: size for 5.5–6kW DC if you want 5kW effective AC output in summer.
- Oversizing for battery-only backup: Buying a 10kW system when you consume 400 units/month doesn't give you "more backup" — it gives you massive excess export. Right-size generation for consumption; size battery separately for backup hours needed.
- Ignoring winter season: Lahore in December generates 35–40% less than June (smog + short days). If your winter bills are also high (gas heating replaced by electric), you need a larger system than summer consumption alone suggests. Calculate annual average, not peak month.
- Believing installer "bigger is always better" advice: Some installers push larger systems for higher margin. Always verify their recommended size against the formula: target kWh ÷ city monthly kWh per kW. If their recommendation is 20%+ above the formula result — ask why.
- Not accounting for panel degradation: Panels lose 0.55%/year. A system that exactly covers your consumption today will cover 88% at year 20. Size with 5–10% extra for graceful long-term coverage.
On-Grid vs Hybrid — Which Should You Install?
| Your Situation | Recommendation | Reason |
|---|---|---|
| Area with 2–4 hr daily shedding | On-grid with net metering | Short outages manageable; lower cost, faster payback |
| Area with 4–6 hr daily shedding | Hybrid inverter, battery optional | "Battery-ready" — add storage later if outages increase |
| Area with 6+ hr daily shedding | Hybrid + 10kWh Pylontech | Generator savings justify battery cost within 2–3 years |
| Currently spending Rs. 8,000+/month on generator | Hybrid + battery immediately | Generator elimination alone pays for battery in 18–24 months |
| Rural with 12–18 hr shedding | Off-grid or large hybrid battery | Grid unreliable; battery must cover full night independently |
Roof Assessment — Before You Size
Before finalizing system size, your roof must be assessed for available south-facing unshaded area. Many Pakistan buyers are disappointed to find their ideal 7kW or 10kW system won't fit after roof assessment.
- Roof space per kW: Each kW of solar needs approximately 6–7 m² of south-facing roof. 5kW = 30–35 m². 10kW = 60–70 m². 20kW = 120–140 m².
- Shading is critical: A water tank, AC outdoor unit, parapet wall, or nearby tree shading even 1–2 panels can reduce entire string output by 15–30%. Have installer do a shading analysis at 11am (solar peak) on your specific roof.
- Roof orientation: True south is optimal. Up to 20° east or west deviation costs only 3–5% generation. North-facing slopes are not suitable for Pakistan.
- Tilt angle: Lahore: 30° optimal. Karachi: 25°. Islamabad: 33°. Flat roof installations use angled mounting at these tilts — adds Rs. 15,000–25,000 to mounting cost but significantly improves generation.
- Roof load: 18 panels (10kW) weigh approximately 560 kg including mounting. Confirm with your contractor that roof structure supports this. Concrete roofs: usually fine. Old tile or corrugated iron: need assessment.
Pakistan-Specific Sizing Scenarios — Real Examples
Scenario 1: Lahore Middle-Class Home (5 bedrooms, 2 ACs)
- 12-month average: 750 units/month | Bill: Rs. 33,000/month
- 80% coverage target: 600 kWh from solar
- Lahore output per kW: 138 kWh/month
- Size needed: 600 ÷ 138 = 4.35 kW → Choose 5kW hybrid
- Battery: 8-hour shedding, 1 AC + basics = 7.2 kWh needed → 2× Pylontech US5000
- Total system: 5kW GoodWe ES + 2× US5000 → Rs. 10–14 Lac | Payback: 2.5 years
Scenario 2: Multan Large Home (3 ACs, high summer bills)
- 12-month average: 1,200 units/month | Summer peak: 1,800 units | Bill: Rs. 55,000/month
- 85% coverage target: 1,020 kWh from solar
- Multan output per kW: 151 kWh/month
- Size needed: 1,020 ÷ 151 = 6.8 kW → Choose 8kW hybrid (buffer for heat + degradation)
- Battery: 10-hour shedding, 2 ACs = 17 kWh → 3× Pylontech US5000 (14.4kWh usable)
- Total system: 8kW GoodWe EM + 3× US5000 → Rs. 18–23 Lac | Payback: 2.8 years
Scenario 3: Islamabad Apartment (1 AC, minimal shedding)
- 12-month average: 350 units/month | Bill: Rs. 15,000/month | Shedding: 2–3 hrs
- 80% coverage target: 280 kWh from solar
- Islamabad output per kW: 124 kWh/month
- Size needed: 280 ÷ 124 = 2.25 kW → Choose 3kW on-grid (no battery needed)
- Battery: Skip — 2-3 hour outages manageable without backup
- Total system: 3kW GoodWe DNS on-grid → Rs. 3–4 Lac | Payback: 1.8 years
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