Summarize
- Lumen measures the amount of light produced by a light source
- Watt measures the energy consumed by a light source to produce light
- LED lamps are more energy efficient than traditional incandescent lamps
- Luminous efficacy is how efficiently electricity is converted into light
- Different rooms require different amounts of lumen for lighting
Lumen and Watt, how do they differ and what do they have in common?
Lumen is a unit primarily used to measure the brightness of a light bulb. A larger lumen volume always indicates a larger amount of light. A watt is a unit of power consumed by a bulb to produce light. The higher the wattage of a lamp, the brighter the light it produces. A 12 W bulb burns much more brightly than a 6 W bulb. At the end of the article, we’ll also cover the term lux, which refers to the amount of light in specific areas of a space. Successful lighting depends on whether there is enough light in the right places to perform the desired tasks.
What is Lumen?
The luminous flux, or lumen output, is an expression of the luminous efficacy of light. It therefore indicates the luminous intensity of light. The higher the lumen value, the higher the lighting efficiency of the bulb, and vice versa. The exact value is provided by the manufacturer, as factors like the shape and color of the fixture’s body and other elements affecting light reflection influence the measurement. Lumen is the best indicator of a light fixture’s total light output. Lumens (abbreviated as lm) therefore express the total visibility of light from any light source to the human eye. Exactly how many lumens are needed to say that we are in a well-lit space? Such an accurate reading can be multiplied by the different uses of the premises. The number of lumens depends on several factors, such as the shape and size of the room, the height of the ceilings, the needs of the person and the type of light source (shade, direct, indirect). According to various sources, the basic amounts are calculated to 1 m2 . In this respect, the size of the room is therefore a decisive factor. Different rooms in the home need different levels of lighting. For the kitchen, 400 – 500 lumens per square metre are needed, while for the bathroom (where make-up is applied) 600 – 800 lumens per square metre can be considered.
What is a watt?
People usually buy each light fixture based on its wattage. But why? People are quite conscious of buying light bulbs after looking at the watts, as this has been easy when incandescent lamps were the only technology available. The higher wattage of the lamp indicated that it was brighter. Because in the days of incandescent light bulbs, everyone knew that the amount of light (and heat) was directly related to the watts. A watt is a unit of power from which the energy consumption of a light source can be determined, in kWh. The Led mixes up this equation dramatically. What we have learned in the past is no longer true in the same way. The wattage still describes the light output of a light source, and LED bulbs are now more efficient and do not use as much energy, thus reducing the size of the electricity bill. But the luminous efficacy per watt varies in LEDs.
Lumens versus watts
Lumens describe the brightness of light sources: the more lumens, the brighter the light produced by the lamp. The number of lumens varies according to the type of light source and the wattage indicates the power consumed by the lamp. If the brightness of a light source increases but the wattage does not, it indicates that more energy-efficient lumens and lower power consumption are being achieved.
Lumen and watt, their relationship
An incandescent lamp with a wattage of 100 W produces an average of 1 600 lumens. It can therefore be said that the output of 1 watt is 16 lumens. This is obtained by dividing 1 600 lumens by 100 W. An LED fixture that produces 1600 lumens of light may consume 14 watts, for example. This means one watt of this fixture generates 114 lumens.
Lumens to watts conversion
Converting lumens to watts unequivocally is not really possible with LEDs, because LEDs have different luminous efficiencies per watt. A LED can produce 130 lm/w, for example, so if you want 1300 lumens, you need a 10 watt LED. Some LEDs designed for long life and high quality colour rendering index, the lm/w figure is lower, as in the example 114 above, but the quality is correspondingly higher. I have written about this in our article: a new energy label for LED lights.
Different lighting technologies and energy efficiency
The table illustrates the specific characteristics of each type of light bulb, including incandescent, halogen, CFL and LED. After looking at the table, you will quickly notice the things that distinguish each type from the others.
| VALUES | INCANDESCENT BULB | HALOGEN | FLUORECENT TUBE | LED |
|---|---|---|---|---|
| Consumption | 100 W | 70 W | 20 W | 12 W |
| Efficiency | 16 lm/W | 22 lm/W | 80 lm/W | 130 lm/W |
| Lifetime (hours) | 1 000 h | 2 500 h | 10 000 h | 50 000 h |
| Price | Cheap | Cheap | Medium price | Expensive |
| Running costs | Very expensive | Expensive | Mid-priced | Cheap |
Lumen and Watt, conversion
Lumen (lm) is the standard unit for luminous flux. It can be expressed as the amount of luminous flux from a light source incident on an area in a unit of time. In contrast, the Watt is a typical unit of time for electrical power. It is measured in joules per second (j /s). Lumens / Watts = luminous efficacy
Explanation of luminous efficacy
Determining luminous efficacy means assessing a light fixture’s ability to convert the electricity it consumes into light — in other words, watts into lumens. The luminous efficacy of older technology lamps was very low, only 12 lm/W, but LED lights today are capable of over 200 lm/W at best. Over 300 lm/W has been achieved from LEDs in laboratory conditions, but such a commercial product would have a very short lifespan, as higher operating temperatures significantly reduce an LED’s longevity. You can read more about this in our article Led can’t take the heat. In LED lights, the fixture’s characteristics—such as color rendering (CRI), lifespan, manufacturing method, and materials—have a strong impact on the final lumen output. With current technology, a luminous efficacy of 135 lm/W at 85 – 95 colour rendering is good. By increasing the colour rendering to between 95 and 100, a good luminous efficiency is 100 lm/W. It is therefore quite clear that current technology offers significant energy saving advantages over incandescent lamps (16 lm/W), but efficiency must not take precedence over other quality factors.
Lumen and wattage recommendation for different rooms
There are many lumen recommendations around the world. In such cases, we’re talking about the characteristics of the fixtures. In lighting design, the concept of lux is used to define the desired level of light. The luminaire is chosen on the basis of the desired luxury levels, i.e. the amount of light in the room. Here, I’ll briefly go over some general guidelines. For example, the Finnish Federation of the Visually Impaired recommends paying attention to good general lighting for both people with normal vision and those with impaired vision. Contrasts and glare in particular are the focus of attention. Power alone does not make a space good lighting-wise. For general educational, customer service, and office spaces, the 500 lux recommendation is good. When choosing light fixtures for different areas of the home, it’s important to consider both the luminous efficacy of the fixture and its suitability for the shape of the space. In addition, the desired style and atmosphere are essential when choosing the light. Purely from a cost perspective, the most efficient way to light a space is to use a few high-output lights, but other factors should also be considered in the design. Based on our experience, recommended lighting levels include the following:
Kitchen
The kitchen, and especially the worktops, are the corners of the house where bright light is essential. For workplace lighting, you should choose a LED light light, for example, which produces around 1 000 lumens/m. It therefore provides enough light for a light level of about 500 lux in a cantilevered aluminium profile. Naturally, the distance from the light source to the surface is one of the factors that will affect this. A more neutral shade of light is recommended to improve contrast.
Living room
The living room is a place where you want to relax enough, and there is room for children to play on the floor. The basic light output is 200 to 300 lux. This can be achieved, for example, in a rectangular space with an area of 20 m² and a ceiling height of 2.5 meters, by choosing 6 units of Round Panel 200 fixtures, each providing 1300 lumens. The light is directed directly downwards from the luminaire, i.e. it is a light luminaire with an opening angle of 110 degrees, i.e. wide. The power consumption of one fixture is 15 W, so the total power with this type of lighting would be 90 W. Roughly speaking, it can be said that 100 W of LED power is sufficient to light a 20 m² living room. This is also obtained, for example, with 6 pcs of 9 W spotlights (e.g. Round 033) with a lumen output light of about 600.
Dining room
The dinner table is a quiet place for the family to relax, and often a warmer light light is all that’s needed, providing 300-400 litres of light on the table. Nowadays, of course, the situation has changed because people work remotely in their homes a lot. Then a variable amount of light is in place.Bedroom
The bedroom is a place of relaxation, with a soft feeling of light and a warm tone. For an adult bedroom, the lighting efficiency is around 200 – 300 lux. In a child’s room, on the other hand, you can have a lot more light for playing and doing homework, around 400-500 lux.
Office
In the workplace, people need brighter light to concentrate fully on their work. The working space should be 800 -1 000 lux.
Bathroom
Bathrooms are where some people want a spa atmosphere. in which case 120 – 200 luchs is good enough. While others just want to do their make-up quickly, and a bright 500 lux of light is not too much. Different light sources should be used in the bathroom as needed, achieving light levels of 100-800 lux. The light intensity can therefore be adjusted as needed.
Discover the technical features
Energy labelling
Before buying LED lights, it is better to check the energy labels. The energy label illustrates the maximum amount of energy a light bulb can consume and is shown on your electricity bill. The energy labels also provide information on the life of the lamp. The new regulations changed the energy labelling of LEDs. I wrote about this in a blog article New energy label for LED lights.
Colour rendering index
The colour rendering index (CRI) is another factor that applies to any light source. It tells you how the colours appear in the light of that particular LED. The index is usually between 0 and 100. If colour rendering is not mentioned, it always raises more questions and so I would not buy such a lamp. A CRI of 85 or more is considered acceptable. Whereas CRI 95 is already excellent and reproduces all colours naturally.
Colour temperature
Colour temperature is the “colour” of white light emitted by a light source, expressed in Kelvin. The colour temperature is usually between 2 000 and 6 500 K. In luminaires, warm white is around 2800 Kelvin, tending towards yellowish or orange. The 4 000 Kelvin scale is a neutral colour temperature, where the shade of light is neither warm nor cold. The cold shade of the luminaires, on the other hand, is around 5 500 Kelvin. The standard daylight for lighting and video set-ups, for example, is typically 6 500 Kelvin, but in living spaces it is quite unnatural for most of the year and most of the day.
Other technical reading
LED lights and price – What makes LED fixtures expensive? CRI and RA – What is the difference between CRI and RA? Make your face beautiful – What is good make-up lighting?
Led lighting expert
LedStore has been an expert in LED lighting and lighting design since 2010. We have our own product design, so our products are technologically state-of-the-art. Products have guarantee for up to 7 years and we also carry out lighting maintenance. We focus on temperature-controlled and high colour rendering lights, so they work brilliantly and last a long time. We carry out hundreds of lighting designs each year for our customers’ projects. Read more here or order a lighting design We offer a service of custom-made LED strips, i.e. custom-made LED strips in aluminium profile. Also installed. Did you know? LedStore offers affordable lighting design for your entire home! Remember that we are always ready to offer our help to you along the way, by email (myynti@ledstore.fi) and by phone (045 251 4510). We love to see the cool things done by our LEDs, and it also helps to provide inspiration for those who are not sure about the power and awesomeness of LEDs. Did you know that we already have over 3 500 pictures of our LED installations in our Gallery!
Photo gallery of Led lights:
Product gallery: Pictures of PRODUCTS in different installation locationsIndirect light: Indirect light in different spacesRoom-specific: Light in different roomsReferences: Complete houses that have been photographedFAQ
1. What is the difference between lumen and watts?
2. Why are lumens more important than watts when choosing lighting?
3. How many lumens are needed in different rooms?
- Kitchen: 400-500 lm/m²
- Bathroom: 600-800 lm/m²
4. How does the energy efficiency of LED lights compare to traditional light bulbs?
5. Why does the wattage no longer tell you how bright the light is?
6. Are lumen and wattage related?
7. How many lumens are in 1 watt?
8. Is 800 lumens too much?
9. How large an area does 1 000 lumens illuminate?
10. Are different amounts of lumen necessary in different rooms?
