Is “unplugging the plug can save electricity” a “pseudoscience”? “Rhythm” is important →

In daily life, do you have the habit of saving energy? For example, in summer, you will try to increase the air conditioning temperature, and usually turn off the lights and electrical appliances. In fact, there is another habit of saving electricity that may be often overlooked by everyone - unplugging household appliances that are not in use.

01 Can unplugging a device save electricity? Is this pseudoscience?

Some people may wonder, when household appliances are not in use, they stop running by turning off the switch. Is it redundant to unplug them? Not only does it cause more trouble, but will frequent plugging and unplugging damage the appliances? The key is, is the idea that unplugging can save electricity "pseudoscience"?

Image source: Pixabay

Let me first state the conclusion. If you just turn off the switch but do not unplug the plug, many household appliances will still be in a power consumption state, so only by completely unplugging the plug can you save electricity. There are two reasons for this.

First, many high-power household appliances, especially those that use remote controls, are not turned off after being turned off, but in standby mode. In standby mode, although the appliance does not appear to be running, some components are still powered on, such as some indicator lights, signal receivers, etc. At this time, the appliance will still generate a small amount of power consumption, which may seem insignificant, but accumulated over a long period of time, it will still generate a lot of power consumption.

Second, even if the household appliances are completely turned off by mechanical switches, as long as the plug is not unplugged, the household appliances may still consume electricity. This is because the power supply standard of my country's national power grid for households is 220 volts AC, but most household appliances cannot directly use 220 volts AC. Therefore, the current needs to go through the process of voltage reduction, voltage stabilization, and rectification from the power supply to the driving appliance. In this process, the transformer and rectifier equipment built into the household appliances, whether it is a coil transformer or a power supply IC chip that rectifies the AC power, will generate static current. These static currents will also consume electrical energy.

Tips

Transformer and rectifier equipment: In household electrical appliances, transformers generally convert 220 volts into a low voltage suitable for driving electrical appliances (the internal circuit voltage of general household appliances is a few volts to tens of volts, for example, the operating voltage of a home desktop computer CPU is generally less than 2 volts), and rectification converts the AC power of the power supply into DC power.

02 In addition to saving electricity, safety is also important

In fact, unplugging electrical appliances when not in use is not only about saving electricity, but also about the safety of household appliances. Because when household appliances are in standby mode, or when transformers and rectifiers consume electricity due to static current, a small amount of heat will be generated and the appliance will be in a state of continuous heating. When the internal ventilation of the appliance is poor due to design problems, the heat will accumulate to a certain temperature, and there is a very small probability that the insulation layer in the circuit will be damaged. When the insulation layer is damaged, it is possible to cause a short circuit in the appliance, causing a leakage accident or even a fire.

Among household appliances, electric water heaters, water dispensers and other household appliances that are not unplugged for a long time are more dangerous. Because these appliances will come into contact with water, if the sealed parts that isolate water in the appliances age or break and cause leakage, they are more likely to cause short circuits and fire accidents than other appliances.

In addition to the home appliances themselves, the quality of various sockets, power strips and other equipment on the market varies. Some poor quality power sockets will accelerate the aging of internal components of the equipment when they are plugged in for a long time, and even cause short circuit failures, causing safety hazards. Therefore, when the charging devices of home appliances and electronic devices are not used for a long time, they must be unplugged to avoid these safety hazards.

03 The “rhythm” of unplugging the plug also has its own rules

From the previous content, we know that for the sake of power saving and safety, it is necessary to unplug household appliances during non-working hours. However, some people may think that plugging and unplugging too frequently is not only very troublesome, but may also cause damage to household appliances. This concern is not without scientific basis in theory. The principle comes from a factor called "surge phenomenon".

Surge, also known as "surge", refers to the inductive pulse interference phenomenon of instantaneous voltage or current overload in the circuit system. When a surge occurs, the voltage or current value in the circuit often exceeds the normal value by several times or even tens or hundreds of times within a few millionths of a second. Surges may occur in thunderstorms or when electrical equipment is connected or disconnected. The instantaneous high voltage generated by the surge phenomenon may indeed cause damage to electrical equipment.

Image source: Pixabay

However, for household appliances, the damage to electrical equipment caused by surges caused by power on and off is basically only theoretical. On the one hand, because the power of household appliances is often small, even if a surge occurs, the instantaneous voltage peak in the circuit will not be too high; on the other hand, as the design technology of electrical appliances becomes more and more mature, circuit designers will protect more sensitive and fragile electronic components by adding surge absorption devices such as TVS diodes, gas discharge tubes, and varistors to the circuit, so the actual probability of surge damage to household appliances is still relatively low.

However, a low probability does not mean an absolute zero probability, especially for household appliances with high power such as refrigerators and air conditioners. If the power supply is plugged in and out too frequently, the equipment may be damaged due to surge. Therefore, we must strike a balance between "saving power and safety" and "avoiding damage from surges" and make different "unplugging" strategies for different appliances and different situations:

1. For electrical appliances with low power and convenient power plugging and unplugging, such as rice cookers, televisions, set-top boxes, stereos, plug-in lighting fixtures and other electrical appliances, you can unplug the power plug immediately after each use to avoid continuous power consumption and eliminate safety hazards.

2. Electric ovens, microwave ovens and other kitchen appliances, as well as washing machines, electric water heaters and other water-related household appliances, should be unplugged when not in use. Especially when you are away from home for a long time, you need to check and confirm to avoid dangers such as short circuits and fires.

3. Air conditioners, electric heaters, electric oil heaters, electric blankets and other household appliances with cooling or heating functions often have seasonal attributes. After using them in the corresponding season (summer or winter), you can unplug the power plug for a long time until the next season.

4. Food storage appliances with refrigeration functions, such as refrigerators or freezers, need to remain powered on due to their special properties, so they should not be plugged in and out frequently. However, in the event of lightning strikes or power outages, the power plug should be unplugged in time and replugged when the power supply is restored to a stable state to avoid surge damage to the equipment. Other high-power appliances should be handled in the same way when they encounter lightning strikes or power outages.

5. Chargers for mobile phones, tablets, etc. should be unplugged in time after they are fully charged to avoid leaving them plugged in for a long time. This will save electricity and avoid potential safety risks.

6. When you are away from home for a long time, be sure to unplug all electrical appliances at home. It is best to turn off the main circuit breaker before going out to completely avoid electrical safety hazards.

If you feel that plugging and unplugging the power plug is too frequent and troublesome, you can buy a power strip or power panel with a built-in power switch. When the corresponding appliance is not in use, you can directly cut off the power through the power switch on the panel, which can also achieve the same effect as unplugging the plug.

Source: Chongqing Science and Technology Museum

Author: CPU, science writer

Audit expert: Li Chunli

Statement: Except for original content and special notes, some pictures are from the Internet. They are not for commercial purposes and are only used as popular science materials. The copyright belongs to the original authors. If there is any infringement, please contact us to delete them.