ElectroHub

Energy and Electricity Bill Calculator

Utilities bill in kilowatt-hours: one kilowatt drawn for one hour. Convert an appliance's rating and running time into units, multiply by the tariff, and the mystery goes out of the bill.

Energy & Bill — kWh = kW × hours

Energy consumed by an appliance and what it costs. One "unit" on the electricity bill = 1 kWh.

Energy per day
Total energy (units)
Estimated cost
  1. 1.Given: load = 1 kW, 5 h/day, 30 days, tariff = 8 per kWh
  2. 2.FormulaEnergy per day = P (kW) × t (h)SubstituteE = 1 kW × 5 hResultE = 5 kWh per day
  3. 3.FormulaTotal energy = E per day × daysSubstituteE = 5 × 30ResultE = 150 kWh (units)
  4. 4.FormulaCost = total kWh × tariffSubstituteCost = 150 × 8ResultCost = 1200
Common trap: kW and kWh are different things: kW is how fast energy is used, kWh is how much. A 2 kW heater run for 30 minutes uses 1 kWh — the bill charges for kWh, never for kW.

The formula

Units (kWh) = (Watts / 1000) × hours ; Cost = units × rate

Watts
appliance power rating
hours
running time over the billing period
rate
tariff per kWh in your local currency

Worked example

A 1500 W water heater used 2 hours a day for 30 days at ₹7 per unit.

  1. Power in kW: 1500 / 1000 = 1.5 kW
  2. Units: 1.5 × 2 × 30 = 90 kWh
  3. Cost: 90 × 7

90 units costing ₹630 a month — from one appliance.

Where you'll use it

Energy audits, comparing appliances, and checking whether that inverter AC really pays for itself. Note that heating loads dominate: a 1500 W geyser for two hours beats a 60 W fan running all day.

The laws behind it

Parts this applies to

Resistor (fixed)Capacitor (aluminium electrolytic)Capacitor (tantalum)LED (light-emitting diode)MOSFETRectifier DiodeSchottky DiodeZener Diode

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