Estimate units from an appliance
Monthly units (kWh) = Watts ÷ 1000 × Hours/day × DaysRated wattage is not always the actual average draw, especially for inverter ACs, refrigerators, pumps and variable-speed appliances.
| Appliance | Assumption | Approx units/month |
|---|---|---|
| 36W BLDC fan | 12 hr/day | 13.0 |
| 80W fan | 12 hr/day | 28.8 |
| 12W LED × 5 | 6 hr/day | 10.8 |
| 1,000W appliance | 2 hr/day | 60 |
Why slab tariffs are not simple multiplication
With slab-based residential tariffs, multiplying all consumption by the highest slab rate is not correct. Units are generally priced across applicable blocks, after which demand, service, meter, VAT or other applicable charges may be added. A calculator should therefore show the tariff effective date and utility/category clearly.
Find where the units go before trying to cut the bill
Long-hour loads
A fan may have low wattage but still use meaningful monthly units when it runs 12–18 hours a day.
Cooling
Actual AC consumption depends on temperature, room heat load, inverter modulation and runtime.
High-watt short loads
Irons, kettles, heaters and pumps may run briefly but add units quickly because of high wattage.
Compare meter readings
The difference between monthly meter readings is the best reality check against appliance estimates.
Sources & references
- DESCO — Current tariff ratesOfficial page listing current and previous retail, bulk and wheeling tariff notices.
- Bangladesh Power Development BoardOfficial power-sector information source.