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   How to convert lumens to watts


   How to convert luminous flux in lumens (lm) to electric power in watts (W).


   You can calculate watts from lumens and luminous efficacy. 


   Lumen and watt units represent different quantities, so you can't convert lumens to watts.


   Lumens to watts calculation formula


   The power P in watts (W) is equal to the luminous flux FV in lumens (lm),

   divided by the luminous efficacy ? in lumens per watt (lm/W):


   P(W) = FV(lm) / ?(lm/W)


   So


   watts = lumens / (lumens per watt)


   or


   W = lm / (lm/W)

   Example


   What is the power consumption of a lamp that has luminous flux of 900 lumens and luminous efficacy 

   of 15

   lumens per watt?


   P = 900lm / 15lm/W = 60W


   Luminous efficacy table


   Light type                                                        Typical luminous efficacy (lumens/watt)


   Tungsten incandescent light bulb                12.5-17.5 lm/W


   Halogen lamp                                                        16-24 lm/W


   Fluorescent lamp                                                  45-75 lm/W


   LED lamp                                                                30-90 lm/W


   Metal halide lamp                                               75-100 lm/W


   High pressure sodium vapor lamp                   85-150 lm/W


   Low pressure sodium vapor lamp                  100-200 lm/W


   Mercury vapor lamp                                              35-65 lm/W


   Energy saving lamps have high luminous efficacy (more lumens per watt).


   Lumens to watts table


   Lumens      Incandescent light bulb watts        Fluorecent  / LED watts


   375 lm            25 W                                                  6.23 W


   600 lm            40 W                                                     10 W


   900 lm            60 W                                                     15 W


   1125 lm          75 W                                                18.75 W


   1500 lm        100 W                                                     25 W


   2250 lm        150 W                                                  37.5 W


   3000 lm        200 W                                                     50 W




Lumens? – Watts the difference?
Watts are out and Lumens are in!
Why?

Ever since bulbs became mainstream everybody has referred to bulbs by their wattage rating.

For example they would go along to their local store, before the days of armchair internet ordering, and buy a 40 Watt bulb, a 60 Watt bulb or 100 Watt bulb. The 100 Watt bulb, as we all know, would be brighter than the 60 Watt bulb and the 60 Watt bulb would be brighter than the 40 Watt bulb.

This was because the more energy you put through an incandescent bulb’s filament the brighter the light you achieved. Most of the energy consumed and paid for by you however, was converted to heat rather than light.

With new technology in lighting and especially with the introduction of LED Bulbs this coarse way of measuring light has been turned on it’s head. A LED bulb (LED stands for Light Emitting Diode) can produce as much light as an incandescent bulb consuming up to ten times more energy.

For example a 6 Watt LED bulb could provide as much light as a 60 Watt incandescent bulb, so buying a 60 Watt light bulb, has now become a little more confusing.
What you want is to buy a bulb with the same brightness as your existing incandescent bulbs – so how can you compare?
Enter the word Lumens!

Lumens are a measure of brightness that for years have enabled lighting engineers to design lights and fittings for all sorts of commercial and industrial applications. They define how bright a light source is and from this the lighting design engineers can establish what fittings and bulbs to fit into different settings, dependant on the task or activities, that the space is being designed for. (ie to ensure that correct brightness of the light is available for the activity which is being planned to be carried out in that particular space)

So given that technologies like LED bulbs produce the same amount of light whilst consuming up to 90% less energy, what you will be looking for is a bulb producing a set amount of light with the least possible energy consumption.

Regulations in the EU and the USA are set to change such that packaging will now provide you with the information, including lumen output, to make a more informed decision about which bulb to choose.

The UK’s Lighting Association estimates the output of incandescent bulbs to be the following;-

25 Watt = 200 Lumens
40 Watt = 400 Lumens
60 Watt = 660 Lumens
75 Watt = 900 Lumens
100 watt = 1190 Lumens

We have found however that many consumers are more than happy to replace their 100 Watt bulb with a LED bulb that emits a lower lumen level than the 1190 Lumens quoted by the Lighting Association.

This is caused by a number of factors such as the colour of the light emitted from a LED bulb (often referred to as Colour Temperature) and Colour Rendering (the ability of the light emitted to reproduce the true colour of the object it is illuminating).
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