Understanding the Packaging - What means Watt?
So you've received your LED light bulbs and you just don't know what all the jargon is. Hopefully we can help you understand your Watts from your CRi.
Firstly you might be wondered why there is so much complicated data on your LED packaging and also the LED themselves. Well that is a result of EU legislation that dictates to LED manufacturers what they have to put on the packaging. Most of it would seem a bit pointless to many of us, but it is all there for a reason. Due to the fact that light bulbs are no longer long thin strands of tungsten filaments and that they are more like miniature computers, you have to put so much extra information that is useful to different sets of users.
Firstly, the list of things that has to be on the packaging:
Nominal useful luminous flux (Useful Lumens to you and I, see our article here that explains all about useful lumens) must be displayed in a font at least twice as large as any display of the nominal lamp power;
Nominal life time of the lamp in hours (not longer than the rated life time);
Colour temperature, as a value in Kelvins and also expressed graphically or in words;
Number of switching cycles before premature failure;
Warm-up time up to 60% of the full light output (may be indicated as 'instant full light' if less than 1 second);
A warning if the lamps cannot be dimmed or can be dimmed only on specific dimmers; in the latter case a list of compatible dimmers shall also be provided on the manufacturer's website;
If designed for optimum use in non-standard conditions (such as ambient temperature must not equal greater than 25 degrees or specific thermal management is necessary), information on those conditions;
Lamp dimensions in millimetres (length and largest diameter);
Nominal beam angle in degrees;
If the lamp's beam angle is greater or equal to 90 degrees and its useful luminous flux (useful lumens) is to be measured in a 120 degree cone, a warning that the lamp is not suitable for accent lighting;
If the lamp cap is a standardised type also used with filament lamps, but the lamp's dimensions are different from the dimensions of the filament lamp(s) that the lamp is meant to replace, a drawing comparing the lamp's dimensions to the dimensions of the filament lamp(s) it replaces;
As you can see with all the things on the packaging, it is no wonder that most people are confused.
So lets go through all these points and find out what they actually mean.
1. Nominal useful luminous flux must be displayed in a font at least twice as large as any display of the nominal lamp power;
Nominal useful luminous flux is the technical term for what you and I would call 'Useful Lumens' so we will refer to it is this from now on. This part of the legislation means that the Useful Lumens has to be displayed 2 times bigger than any wattage that is listed on the packaging, so if you find some packaging that has a useful lumen value hidden away, then it is likely that the manufacturer isn't 100% aware of this legislation which would indicate that it might not be the best LED bulb in the box, so just be a bit careful and definitely don't spend a fortune on these lamps.
If you were wondering, nominal is a word that confused us a bit as well, because the legislation refers to Nominal ..... and Rated ..... for the same ..... (I put ..... because there are at least 3 values that have a nominal and rated value, Lifetime, Lumens, Wattage etc). It isn't 100% clear and so we interpret Nominal to mean the time when after the light bulb is switched on, the values of wattage and lumens stabilise after about an hour (after the warm-up), this would be the nominal value, and rated is the theoretical value that light bulb should be at if conditions for running the bulb were 100% perfect.
2. Nominal life time of the lamp in hours (not longer than the rated life time);
There is that word nominal again, but this time for the nominal life time of the lamp in hours, so to you and me this would simply refer to the lamp life.
It is important to understand that this is an AVERAGE, if it says 25,000 hours on the box then some will last longer and some will fail before. It ALSO means that they may become less bright over time and at 25,000 hours should be around 70% of it's original brightness.
3. Colour temperature, as a value in Kelvins and also expressed graphically or in words;
The colour of white light is technically expressed in Kelvins, but for domestic purposes all we need to know are the following numbers:
2700K means Extra Warm White light - same colour as traditional incandescent
3000K means Warm White - similar colour to halogen light
4000K means Cool White - type of light you would find in an office environment
6000-6500K means Daylight - a very bluish white light that is commonly used in craft lighting and is a very bright, stark white light that can aid poor eyesight or to assist SAD sufferers.