How to Size a Solar System for Load Shedding in Bangladesh (Step-by-Step)
Nov 5, 2026 . Alobari Team
Quick answer: Add up the watts of everything you want to run during load shedding, multiply by the hours you need, then size the battery for that energy, the panels to refill it in one day (Bangladesh averages about 4–5 peak sun hours), the charge controller for panel watts ÷ battery volts, and the inverter 20–30% above your running load. A typical fan-lights-router-TV backup of ~250W for 4 hours needs about a 12V 100Ah LiFePO4 battery, ~300–400W of panels, a 30A MPPT controller and a 500W pure sine wave inverter.
Step 1: List your loads
| Appliance | Typical watts |
|---|---|
| Ceiling fan | 60–80W |
| LED bulb | 9–12W |
| Wi-Fi router / ONU | 10–20W |
| LED TV 32" | 40–60W |
| Laptop | 45–65W |
| Small refrigerator (average running) | 100–150W |
Example: 2 fans (140W) + 5 LED bulbs (50W) + router (15W) + TV (50W) ≈ 255W.
Step 2: Daily backup energy
Energy (Wh) = watts × hours. If load shedding totals 4 hours: 255W × 4h ≈ 1,020Wh.
Step 3: Battery size
Battery Wh needed = backup Wh ÷ usable depth of discharge ÷ 0.9 inverter efficiency.
- LiFePO4 (about 90% usable): 1,020 ÷ 0.9 ÷ 0.9 ≈ 1,260Wh → a 12V 100Ah LiFePO4 (1,280Wh), e.g. four EVE LF100LA 100Ah cells in series with a BMS.
- Lead-acid (about 50% usable for long life): 1,020 ÷ 0.5 ÷ 0.9 ≈ 2,270Wh → about 12V 200Ah.
Step 4: Solar panels
Panel watts ≈ daily energy ÷ peak sun hours ÷ 0.75 (losses). For 1,020Wh: 1,020 ÷ 4.5 ÷ 0.75 ≈ 300W. Add more (400W+) if you want to recover fully on cloudy monsoon days.
Step 5: Charge controller and inverter
- Controller: 400W ÷ 12V × 1.2 ≈ 40A — choose EPEVER TRC4210 40A MPPT. On a 24V battery the same panels need only ~20A (EPEVER TRC2206).
- Inverter: running load 255W plus 20–30% headroom → Corechain CJ-1000 500W pure sine wave. Running a fridge too? Step up to the 800W CJ-1600.
Worked examples
| Need | Battery | Panels | Controller | Inverter |
|---|---|---|---|---|
| Lights + 1 fan + router, 4h | 12V 50–100Ah | 150–200W | 20A | 500W |
| 2 fans, lights, TV, router, 4h | 12V 100Ah LiFePO4 | 300–400W | 30–40A MPPT | 500W |
| Above + fridge, 6h | 24V 100Ah LiFePO4 | 800W–1kW | 40A MPPT | 1,500W (24V model) |
Tips for Bangladesh
- Use 24V or 48V for systems above ~1kW — currents and cable sizes drop.
- Mount the controller indoors, away from rain and direct sun; summer heat above 38°C shortens electronics life.
- Fit DC breakers or fuses and earthing on rooftop arrays — lightning is common in the pre-monsoon season.
বাংলায় সংক্ষেপে
১) কোন কোন ডিভাইস চালাবেন তার মোট ওয়াট বের করুন। ২) লোডশেডিংয়ের ঘণ্টা দিয়ে গুণ করে Wh বের করুন। ৩) সেই অনুযায়ী ব্যাটারি (LiFePO4-এ ~৯০% ব্যবহারযোগ্য)। ৪) প্যানেল ≈ দৈনিক Wh ÷ ৪.৫ ÷ ০.৭৫। ৫) কন্ট্রোলার = প্যানেল ওয়াট ÷ ব্যাটারি ভোল্ট × ১.২, ইনভার্টার লোডের চেয়ে ২০–৩০% বড়।
Need help choosing?
Call or WhatsApp Alobari at +880 1611-846093 with your panel size, battery and the appliances you want to run — we will recommend the right setup. Cash on delivery and delivery to all 64 districts of Bangladesh.
