When to turn off lights: MythBusters reveal true costs

Rising electricity prices are affecting us more and more. In the search for saving methods, it's worth paying attention to lighting issues, especially since a long-circulating myth can be misleading. Gadgetomaniac journalist Karol Kołtowski checked whether you should always turn off the light when leaving a room, and if so, when it’s worth doing.

As a rule, lighting should be turned off when it's not needed. During the day, it is worth maximizing the use of natural sunlight. However, when using artificial lighting, it should be done wisely, turning off the light when it’s not needed. However, a popular myth suggests that this isn't always worth doing.

For years, it has been believed that a short turn-off of the light is not cost-effective and that it is better to leave it on if you are leaving the room "for a moment." But how long is a moment? For some, it will be two minutes, for others, five, and still others talk about fifteen minutes. This, however, is not true.

This topic was thoroughly investigated in the show "MythBusters." The results of the experiment are described on vanderbilt.edu. The researchers tested five types of lighting:

        
• traditional 90 W light bulb
• 10 W compact fluorescent lamp
• 70 W halogen
• 1 W LED
• 10 W fluorescent

The key element of the study was to check how much energy each light source uses during startup and compare this value with hourly energy consumption (power of the device multiplied by an hour, expressed in watt-hours - Wh).

The "MythBusters" experiment brought surprising results. It turned out that in some cases, it is more cost-effective to turn off the light after less than a second. Here are the detailed results:

        
• traditional light bulb - 0.36 seconds
• compact fluorescent lamp - 0.015 seconds
• halogen - 0.51 seconds
• LED - 1.28 seconds
• fluorescent - 23.3 seconds

Energy consumption is not everything, though. The durability of the bulb is also important, expressed not only in hours but also in switching cycles. It's important to remember that turning off the light for a few seconds can significantly shorten the lifespan of the bulb, which might lead to additional costs associated with its earlier replacement.

From an energy perspective, it is worth turning off most types of lighting when leaving a room. The exception is classic fluorescent lamps, which need to be on for more than 23 seconds before they consume as much energy as their startup requires.

In practice, however, it is recommended to avoid turning off the light for a few or several seconds. However, if you are leaving the room for a few minutes, turning off the light can be cost-effective. This particularly applies to LED sources, which are very durable and resistant to frequent switching on and off.