What is a Kilowatt-Hour? To have a basic understanding of energy use in your home and how to curb it, it is essential to have a basic understanding of the kilowatt-hour. An appliance's wattage, put simply, is the amount of power it consumes per hour of use. That unit is important because it is used in determining the kilowatt-hour usage of your home, and therefore, your bill. To figure out how much energy a particular appliance in your home uses, simply find the wattage of that appliance (it should be listed somewhere on the appliance). If the wattage is not shown, it can be calculated by finding the amperage and voltage ratings on the appliance and multiplying the two numbers (Amps x Volts = Watts). Once you have the wattage, multiply it by the number of hours per day the appliance operates, and divide that number by 1000. You have just determined how many kilowatt-hours per day the appliance uses. An approximate monthly usage can be determined by multiplying that number by 30 days. You may then multiply the monthly kWh usage by the appropriate rate you pay to determine how much that appliance costs per month to operate. A worksheet (PDF text version) is provided which will allow you to figure an approximate usage for your entire home. How to read your meter.