For some appliances you can easily determine how much energy they consume, while for others you need to do some calculations or even use a device to track the average power consumption. In this article I will explain how to determine energy consumption for different kind of appliances.
Based on consumption patterns, we can put the appliances in 3 main categories: Constant power On/Off appliances ( blenders, hair dryers, light bulbs ), Variable power appliances ( Computers, TVs, electric oven ) and Automated appliances ( refrigerators, air conditioners, water heater ). I will detail each type of appliances and how can you find out how much electric energy it consumes hourly, monthly or yearly.
Constant power appliances
When you buy constant power appliances, the power value is wrote on the box or in the product specifications. An yearly average will not be shown because it is irrelevant in this case. If you want to know how much power will consume in a month if it will stay always on multiply the hourly value with 730. If you want to know the yearly figure multiply with 8760. However, most constant power appliances will not be always on, so the power consumed in a month or a year depends on how much you use it. Try to figure out how many hours you use it on average each day. Now you have the daily average and you can do the math to figure out monthly and yearly usage, or you can use our energy consumption calculator.
If you don’t know the power rating of your new appliance or you have an old appliance, you can use a power meter. You can simply see how much power the appliance consumes per hour, or, if you don’t want to guess the average daily usage you can also use the power meter to exactly determine the average power consumed per day. Leave the power meter on for about 2 weeks, and then divide the total power consumed to the number of days you kept it. You will have a good estimate on how much power it consumes on average, and how many hours it stays on on average each day. This number will help you to figure out if it is worth to replace the appliance with a new or more economic one.
In this category you can put all appliances that consumes constant energy during the time they stay on. For example, a light bulb will always consume the same power when turned on.
Variable power appliances
Unlike constant power appliances, the variable power appliances does not consume the same amount of energy for the duration they stay on. For example, an electric oven will consume maximum power at first, but as the temperature goes up, it will consume only to maintain the set temperature inside. The power consumption depend on what you put inside, how cold it is in the room, how many times you open the oven door, how high is the temperature you set. This makes it harder to figure out how much electric power is consumed just by looking on the box or on the instructions, so the best way to exactly find out how much power it uses is to use a power meter. Using it you can figure out: what is the average hourly consumption, what is the average daily consumption and how many hours it stays on per day on average. it is important to know how much power your appliances eat so you can decide if it is worth to buy a new and more economic appliance or if you should use it less often to lower the electricity bill.
Other appliances that consume variable power can be PCs and laptops, TVs, monitors. Their power consumption is influenced by how intensive they are used, by brightness, what colors are displayed. The seller will usually say the maximum power usage but it is irrelevant for determining average power usage. The best way is to use the power meter. The most important factor that influences the power usage is the technology used and size. For example, an LED TV screen will consume less than a TFT display of the same size.
Automated appliances.
These are appliances that are projected to stay on all the time, despite the fact that they are most of the time on idle or at minimum power usage. In this category you can put refrigerators, air conditioners, water heaters, and many other appliances that only start when needed. Their power efficiency will determine the power usage, but the actual wattage is determined more by the usage and environment. When you buy a new automated appliance, you will see an energy star rating. They also give an average power consumption in kilowatts per year. This amount is calculated in a standard environment and is is much smaller than consumption in real environment.
To figure out how much an old automated appliance consume, you can use a power meter and leave it for at least few days. The more the better results you will get. Divide the power shown with the number of hours it stayed on and you get the hourly average. Multiply it with 8760 to get the yearly average usage.