A high electricity bill often feels mysterious until you calculate appliance use in units. The basic formula is simple: watts, hours, and days. The final rupee cost depends on your local tariff, slab, fixed charges, taxes, and state DISCOM rules.
What one electricity unit means
One electricity unit usually means one kilowatt-hour, written as 1 kWh. If a 1000-watt appliance runs for one hour, it uses about 1 unit.
Units = Watts / 1000 x Hours used x Days used
Example: fan usage
Fan wattage: 75 watts Use: 10 hours per day Days: 30 Units = 75 / 1000 x 10 x 30 Units = 22.5 kWh
Example: geyser usage
A geyser can consume more power because its wattage is high, but actual use depends on heating time, thermostat behavior, water temperature, and household routine.
Geyser wattage: 2000 watts Use estimate: 1 hour per day Days: 30 Units = 2000 / 1000 x 1 x 30 Units = 60 kWh
Example: AC usage
AC calculation is harder because compressor cycling, room size, temperature setting, insulation, star rating, and inverter behavior matter. Use the label and manual for better estimates, not only a rough online number.
Why rupee cost is not universal
Electricity rates vary by state, DISCOM, consumer category, slab, fixed charges, taxes, and subsidy rules. Do not use a random rate from another city. Check your latest bill.
Monthly appliance table
| Appliance | What to check |
|---|---|
| AC | Label, hours, setting, room heat. |
| Geyser | Wattage and actual heating time. |
| Fridge | Age, star rating, door opening, placement. |
| Fan | Wattage and daily hours. |
| Washing machine | Cycle length and heating use if any. |
For related home energy planning, read how to reduce monthly electricity waste at home, how to choose a budget smart plug, and how to safely choose a heavy-duty smart plug for high-load appliances.
FAQ
Can I multiply units by one fixed rupee rate?
Only as a rough estimate. Your actual bill may include slabs, fixed charges, taxes, and other adjustments.
Which appliances usually matter most?
High-wattage and long-running appliances such as ACs, geysers, old refrigerators, and heaters usually deserve the first check.