How to Measure Home Appliance Energy Usage

Home meters measure home energy usage; clamp-on-ammeters measure individual appliances.

Measuring the energy consumption of your house is a meticulous job. Understanding your electricity consumption better will help you to conserve energy. Estimating the energy consumed by your home appliances will help you to determine your electricity loads, and help you to decide whether you should invest in more energy-efficient appliances. Wattage (the maximum power drawn by an appliance), can usually be found on the back or bottom of an appliance, or on its nameplate.

Things You'll Need

• Clamp-on-ammeter

Instructions

1. Calculate the wattage of the appliance if it is not listed on the nameplate. Multiply the current it draws by the voltage used. Most appliances use 120 Volts, with the exception of heavier devices such as clothes dryer and electric cooktops, which use 240 Volts. Some appliances have the current (in Amperes) listed instead of the wattage.

2. Use a clamp-on-ammeter --- a common electrician's tool for measuring the current --- to measure the current if neither the current nor the wattage are listed on the device. Clamp the ammeter around one of the power wires of the appliance (usually found within its power box) while the device is running. The display will show the current. Do not clamp around multiple wires at once, as this will throw off the reading.

3. Calculate the appliance's daily energy consumption in Kilowatt-hours (kWh) by multiplying the wattage times the number of hours the appliance is used per day, then dividing by 1,000. Multiply this by the number of days the appliance is used in a year for annual consumption.

4. Calculate the actual operation hours for appliances such as refrigerators that cycle on and off while they are plugged in by dividing the total number of hours that your appliance is plugged in per day by three. Most common devices such as televisions, computers and kitchen appliances continue drawing a small amount of power even while they are switched off. This increases their consumption by a few watt-hours as long as the device is still plugged in, even when it is not in use.

5. Take a meter reading if you want to calculate the total daily energy consumption of all of the appliances operating in your house. Your electric meter has five dials with numbers 0-9 on each dial. Record the numbers, reading them from right to left (if the pointer is in between two numbers, take the lower reading). Subtract this number from the next day's reading to find the energy consumption for one day. Subtract it from the next month's reading for the month, and so on. Multiply the difference by the Kilowatt-hour factor printed on the meter.

References

• Energy Savers: Estimating Appliance and Home Electronic Energy Use
• Standby Power: Frequently Asked Questions