Energy Cost Calculator (kWh)

Enter the power of an appliance, how many hours per day you use it, how many days, and your electricity rate. The calculator works out the kilowatt-hours consumed and the total running cost.

Results update as you type.

How It Works

The energy cost formula

Energy use and running cost follow directly from power, time and the electricity tariff:

  • Energy per day (kWh) = Power (W) ÷ 1000 × Hours per day
  • Total energy (kWh) = Energy per day × Days
  • Cost per day = Energy per day × Rate ($/kWh)
  • Total cost = Total energy × Rate ($/kWh)

Worked example

A 1,000 W (1 kW) appliance running 5 hours per day for 30 days at $0.30/kWh:

  • Energy per day = 1,000 ÷ 1,000 × 5 = 5 kWh
  • Total energy = 5 × 30 = 150 kWh
  • Cost per day = 5 × $0.30 = $1.50
  • Total cost = 150 × $0.30 = $45.00

Motor loads work the same way once you know the input power. A borehole pump moving 4 m³/h against 30 m of head needs about 0.33 kW of hydraulic power, which is roughly 0.64 kW drawn at the terminals once pump and motor efficiency are accounted for -- the pump power calculator gives that figure from the duty point. Run it 6 hours a day at $0.30/kWh and it costs about $1.15 a day, or $35 a month.

Frequently Asked Questions

How do I calculate the running cost of an appliance?

Divide the appliance wattage by 1,000 to get kilowatts, then multiply by the hours of use to get kilowatt-hours (kWh). Multiply the kWh by your electricity rate to find the cost. For example, a 2,000 W heater running for 3 hours uses 6 kWh; at $0.25/kWh that costs $1.50.

How do I convert watts to kWh?

Divide the wattage by 1,000 to get kilowatts, then multiply by the number of hours of use. One kilowatt-hour is the energy consumed by a 1,000 W device running for exactly one hour. A 500 W device running for 4 hours uses 2 kWh.

What is a kilowatt-hour (kWh)?

A kilowatt-hour is a unit of electrical energy equal to 1,000 watts of power sustained for one hour. It is the standard billing unit on electricity tariffs in the UK, US, Australia and most other countries. Your electricity bill typically shows how many kWh you have consumed in the billing period.

How much does it cost to run a typical household appliance?

At $0.30/kWh: a 60 W LED TV for 4 hours a day costs roughly $2.16/month; a 1,500 W kettle used 10 minutes a day costs about $2.25/month; a 3,000 W electric shower for 8 minutes a day costs roughly $7.20/month. Use the calculator above with your own wattage and rate for an accurate figure.

How can I reduce my electricity bill?

Focus on high-wattage appliances that run for long periods, as they dominate your bill. Replacing an old 150 W incandescent lamp with a 10 W LED saves 140 W for every hour it is on. Off-peak tariffs, smart plugs with timers, and energy-efficient ratings (A+++ in Europe, ENERGY STAR in the US) all help. The calculator lets you compare scenarios by changing the wattage or hours to see the cost difference.

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