Understanding Electricity Bills and Load Shedding in Bangladesh
Electricity consumers in Bangladesh—whether served by DESCO, DPDC, WZPDCL, NESCO, or Bangladesh Rural Electrification Board (BREB / Palli Bidyut)—often observe non-linear jumps in monthly utility statements.
Understanding the mathematical structure of Bangladesh Energy Regulatory Commission (BERC) step tariffs and sizing an efficient Home IPS (Instant Power Supply) or Rooftop Solar PV installation can save significant household capital.
1. BERC Residential (LT-A) Tariff Step Slabs
Residential electricity billing in Bangladesh is structured into tiered progressive step slabs:
| Step Tariff Tier | Monthly Consumption (kWh / Units) | Energy Rate (BDT / Unit) | | :--- | :--- | :--- | | Life Line | 0 – 50 Units | ৳ 4.63 | | Step 1 | 0 – 75 Units | ৳ 5.26 | | Step 2 | 76 – 200 Units | ৳ 7.20 | | Step 3 | 201 – 300 Units | ৳ 7.59 | | Step 4 | 301 – 400 Units | ৳ 8.02 | | Step 5 | 401 – 600 Units | ৳ 12.67 | | Step 6 | Above 600 Units | ৳ 14.61 |
Ancillary Charges
In addition to the base energy charges calculated across the slabs:
- Demand Charge: Fixed monthly charge per sanctioned kilowatt (typically ৳ 42 / kW).
- Meter Rent: Standard single-phase digital or smart prepaid meter rent (typically ৳ 40 / month).
- Value Added Tax (VAT): Strictly 5% applied to the sum of energy charges and demand charges.
2. How to Accurately Size a Home IPS and Battery
When power interruptions occur, an IPS converts DC energy stored in lead-acid tubular batteries into 220V AC household electricity.
Step 1: Calculate Total Running Wattage
Sum the active operating wattage of devices required during an outage:
- Ceiling Fan (BLDC): ~35W each (Standard AC Fan: ~75W each)
- LED Tube / Bulb: ~15W to 20W each
- Wi-Fi Router + ONU: ~15W
- Laptop / PC: ~65W to 120W
Total Running Load = Σ (Device Wattage × Count)
Step 2: Determine IPS Inverter Capacity (VA)
Inverters are rated in Volt-Amperes (VA). Assuming a typical domestic power factor (PF) of 0.80:
Required Inverter VA = Total Running Watts / 0.80
For a 400W running load, an inverter of at least 400 / 0.80 = 500 VA (or standard 800 VA to 1000 VA) is recommended.
Step 3: Size Deep Cycle Tubular Battery (Ah)
To support a load for T hours using a 12V DC battery with an inverter efficiency (85%) and depth-of-discharge limit (80%):
Battery Capacity (Ah) = (Running Watts × Desired Backup Hours) / (12V × 0.85 × 0.80)
For example, supporting 300W for 4 hours requires:
Capacity = (300 × 4) / (12 × 0.85 × 0.80) = 1200 / 8.16 ≈ 147 Ah
A standard 150 Ah or 200 Ah tall tubular battery ensures reliable service life exceeding 4 to 5 years.
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