What does LED Colour Temperature Mean?
"3000K, 4000K, Cool White, Daylight. All I want is a LED bulb." It does seem confusing all these different ways of expressing the colour of a LED lamp. But how can you choose the right lamp for you and what is the meaning of the terms used for LED lamps. Let's start by demystifying the term "colour temperature".
There are certain objects (called black body radiators) that allow you to give a pretty close approximation of its temperature (in Kelvin or K) by just looking at its colour. Remember Kelvin, Fahrenheit and Celsius are just ways of expressing temperature.
For example if you saw a cold unpainted metal poker you could probably guess its temperature by observing its colour. You might guess it is at room temperature (i.e. 20 degrees C which corresponds to 293 degrees Kelvin). But would that be the case if the same metal poker was glowing a red/orange colour? Just by looking at the colour you would determine it is too hot to handle. You've determined its temperature by its colour. Possibly it would have a temperature of 745 degrees C which corresponds to 1020 degrees Kelvin. A crude example but hopefully you're getting the gist of the term "colour temperature"
Let's take now an example using a 100W incandescent bulb; you know the one with the filament inside. When switched on the glass outside may be between 65 and 150 degrees Celsius. However the filament inside glows at a much higher temperature. In fact the temperature of the filament may be 2500 degrees Celsius or 2773K; approximately 3000 Kelvin (3000K) which we often call "warm white". Hopefully the penny is starting to drop.
Let's take another example. According to Wikipedia the sun's outer shell (photosphere) has a temperature of 5499 degrees Celsius which corresponds to 5772K (Kelvin); approximately 6000K. Guess what an LED lamp with a colour temperature of approximately 6000K is called? It's often described as "daylight" because it corresponds to the sun's outer colour temperature and the light produced.
So the gist of all this. If you want an LED lamp that corresponds to the colour of the old 100W incandescent lamps then go for a colour temperature around 3000K, "warm white". If you want a lamp that approximates to daylight, then go for one around 6000K and if you want something in between then go for one in between such as "cool white" which often lies between 3000K and 6000K. Just be careful however with the expression "cool white". To some it represents a colour temperature of around 4000K and to others it refers to a colour temperature of around 7500K so verify what colour temperature they are refering to. On this website "cool white" refers to 4000K.