When you’re buying LED light bulbs, one of the specifications is whether they’re warm or cool. This has nothing to do with how hot they get (all LEDs give off very little heat). It refers instead to the “colour temperature” (just to confuse things further). In this article, we’ll explain what all this means, and how it should influence your purchasing.

Colour temperature

Everyone is familiar with the visible spectrum. We see it in rainbows and when we refract white light through a prism. Although we might recognise it as red, orange, yellow, green, blue, indigo and violet, there’s nothing particularly special about these colours. There are infinite wavelengths between red and orange, for example. The visible spectrum contains every possible wavelength of light that is detectable by our eyes. 

The colours in the red to yellow zone are called “warm” colours, and those in the green to violet part are called “cold” colours. It’s a useful way of describing the mood certain colours evoke in humans. Oranges make us think of tropical sunsets and fireplaces, while blues make us think of snow and ice.

Warm and cool LEDs are “tuned” to certain ranges along the spectrum and we call this a bulb’s “colour temperature”. The light won’t be a one wavelength, but a range of wavelengths in the “warm” or “cool” part of the spectrum. So when describing warm and cool lights, we don’t use a wavelength, but a K (Kelvin) measurement:

  • 2000–3000 K is warm white
  • 3000–4500 K is cool white
  • 5000–6000 K is daylight white

Setting the mood

LED bulbs can be made in a range of colours, and by mixing a red, yellow and blue trio (or indeed cyan, magenta and green) we can achieve any colour we want. But still, the coolness or warmth of the bulb is noticeable to humans. 

When to use warm lights

Warm LEDs lean towards the red, yellow or orange side of white. They roughly imitate the traditional glow of a tungsten bulb. Because that kind of light is produced by heating up a metal filament until it glows, it’s not surprising that it has a warm, fiery feel. 

For the domestic setting, such as lighting a living room or bedroom, a warm light usually seems more homely. That might be because it mirrors traditional light sources such as fires, gas lights, candles or tungsten light bulbs. But it generally reduces eye strain, especially as day turns to night.

There’s some evidence to suggest that being exposed to blue light in the evening affects our body clock and sleep patterns. If true, a warm light at night would help to rectify that. 

When to use cool LEDs

Cool white LEDs, on the other hand, seem a little starker to the human eye. They’re more akin to midday sunlight on a winter’s day, or a bright spotlight. Traditional fluorescent tubes, like people used to have in their kitchens, also tended towards the cool end of the spectrum, generally purple. Tubes do come in various temperatures, however.

Cool lights are at the bluer side of white. While they aren’t as relaxing and inviting, they do have their uses. Cool lighting is generally better when you’re doing intricate work, whether that’s crafting, electronics, woodwork, applying makeup, painting or even cooking. You just get to see more detail. (But see daylight white, below.) Bathrooms are also a good place to use cool white bulbs, as they can help with jobs like shaving or cleaning.

It’s also useful if you are lighting up a large area, especially if the lights are mounted in a high ceiling. Warm light tends to be a little softer for a given wattage, so doesn’t carry as well. And if you’re augmenting natural light, for example in a conservatory, outbuilding, portico, hallway or marquee, cool lighting is closer to nature, so won’t look as “dirty” or dim.

Should you use daylight LEDs?

The vast majority of domestic LEDs sold are cool or warm white. Daylight white is another option, but they tend to be used in more specialised settings. Examples include film, photography and design studios, nail bars, retail, offices, light boxes, signage and so on – anywhere that needs really good quality, bright and neutral lighting.

There’s nothing to stop you having it in your home, and there could be applications where it would work, but for most domestic needs, a bright cool light will do the trick. It all comes down to preferences, really.

Daylight white might also be useful in combating SAD – seasonal affective disorder. That’s where people feel gloomy and depressed in winter because of the lack of daylight hours and intensity. Many people believe that having daylight temperature lighting can help to lift the mood.

Find your perfect bulb at ACAS Electrical

Whatever colour temperature you want, you’ll find a brilliant range of LED bulbs at ACAS Electrical. You can filter by colour, fitting and shape, so you’re definitely going to find the ones you need here. And if you need any help, just ask!

Some of our products come with colour selectable lighting which allows for the transition between cool, warm and day light with the flight of a switch or dimmer.