Energy saving lamp: how does the watts conversion?

The classic light bulb left us forever a few years ago - energy saving lamps have often replaced it. But problems still causes the watts conversion between light bulb and energy saving lamp. You can read here how it works.

Ban the light bulb

Classic bulbs are banned since the end of 2012, and are no longer commercially available. The reason for this was the bad energy efficiency of the light bulb. A classic light bulb actually converts only 5% of the absorbed energy into light. The rest is practically lost.

Energy-saving lamps convert a much higher percentage of the energy into light - generally around 80% more efficient than the traditional light bulb.

Differences in performance

The recorded electrical energy is expressed in watts, therefore very high wattages are used for a given light output because of the low efficiency of the bulb. In contrast, the much more efficient energy-saving lamp needs a much lower wattage in order to produce the same amount of light.

The only problem is that the wattage of the bulb as a measure of luminosity in the many decades have gone into flesh and blood. We are still largely based on the known sizes if we want to specify the brightness or estimate ("a 60-watt bulb"). The wattage of old light bulbs are a benchmark for us.

Conversion of light bulb to energy saving lamp

The conversion is not completely accurate - you can only approach with approximate values. In addition to the wattage also counts the number of lumens of the bulb, which should always take something into account.

A high number of lumens means a larger light output in the energy-saving lamp, so the wattage can then be a little lower (by a few watts lower). The light color also has a certain significance for the luminous efficacy that can be achieved.

Calculation path by wattage

A rule of thumb

Wattage of the bulb / 5 = Wattage of the energy saving lamp

But add a few watts to your results to be on the safe side. You should definitely admit about 10% to the calculation result.

To replace a 100 watt bulb, you will need a 20 watts energy saving bulb, in practice you will be in most cases with 22-23 watts correctly.

Calculation by lumen

You can also use the light output as the conversion path. For this you only have to convert the "old" Watt values ​​of the light bulb into lumens. The following table shows which values ​​apply.

The unit lumen is an independent value that directly describes the light output of the bulbs. This allows you to compare the values ​​directly and thus find the right energy-saving lamp easily.

Conversion wattage of the bulb in lumens

Wattage of the bulbLumen number
25 watt light bulb230 lumens of luminosity
40 watt bulb430 lumens of luminosity
60 watt bulb730 lumens of luminosity
100 watt light bulb1,380 lumens of luminosity

Tips & Tricks

However, you should avoid energy-saving lamps as much as possible. They have some serious disadvantages compared to modern LED bulbs and can be hazardous to health. For LED luminaires, approximately the same wattage numbers apply as for energy-saving lamps; they are only slightly below the calculation result (around 10% less than the computer result).

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