Electric usage is measured in kilowatt-hours.

1 watt-hour is the equivalent of 1 watt of power used for 1 hour.

1 kilowatt-hour is the equivalent of 1000 watt-hours used for 1 hour.

Three values are needed to calculate the cost to use an appliance:

• The power rating or wattage of the appliance. This is found on the appliance e.g. 50W or 1800W.

• The time the appliance is switched on in hours (or minutes ÷ 60)

• The cost per KWh.

1. Appliance wattage ÷ 1000 = kilowatts (kW)

2. Kilowatts × (time appliance is switched on in hours) = kilowatt hours (kWh)

3. Kilowatt hours x cost per KWh is what you pay for that appliance to run.

Example 1: 100W light bulb on for 24 hours where the cost per KWh for electricity = 8.7¢ (.087)

(100 ÷ 1000) × 24 = 2.4 kWh used

2.4 kWh × 8.7¢ = 21¢

This means that it costs 21¢ to use a 100 Watt light bulb for 24 hours.

Example 2: Equivalent energy saving CFL light bulb (20W) for 24 hours

(20 ÷ 1000) × 24 = 0.48 kWh used

0.48 kWh × 8.7¢ = 4¢

This means that it costs just 4¢ to use an equivalent low energy light bulb for 24 hours.

As you can see, using a low energy saving light bulb in place of an ordinary light bulb will save you over 14 cents every 24 hour period your light is on.

Multiply this times the number of light bulbs in your home or business and the savings could be substantial.

More information on Compact Fluorescent Lights can be found here.