The Difference Between Watts and Lumens – LED Lighting Explained

by | Nov 3, 2018

While LED lights have become much more common in recent years, the terminology is still unfamiliar to many of us. How many lumens do you need? What colour temperature should you buy? We explain all below. 

How are LEDs different?

LEDs lights work completely differently to classic, incandescent lights. They use a semi-conductor, or microchip, that emits light when an electrical current passes through it. They don’t get hot like traditional bulbs do and, as LEDs are far more efficient at converting electricity into light, they use up to 90% less energy.

How many watts in an LED bulb?

We are used to buying bulbs according to their watts (W) – however wattage is actually a measure of energy use rather than the brightness. Therefore, when you purchase a 50w bulb, it will consume around 50w of energy.

Depending on the manufacturer and the technology, a 50w halogen bulb can typically be replaced with a 6 or 7w LED bulb. In terms of energy consumption, this clearly provides a significant cost saving.

Lumens (lm) is a more accurate measure of brightness, and most LED bulbs sold now state the lumens along with wattage (or amount of energy they use).

The table below gives an indication of the lumens in standard, incandescent bulbs. When you’re buying LED lights, take notice of the lumens rather than watts for an accurate measure of brightness. For instance, if you want an LED bulb equivalent to a 75w standard bulb, look for one at about 1100 lm.

Colour temperature

Another feature of LED bulbs is that they come in different colour temperatures – as illustrated in the picture at the top of this blog. To understand colour temperature, think of the soft, orange glow produced by a fire as compared to the harsh, blue light of day. It’s not just the brightness that makes a difference; it’s the warmth or coolness of the light.

Colour temperature is measured in kelvin (K) as seen in the chart below. The lower the Kelvin rating, the yellower and warmer the light appears. Conversely, the higher the Kelvin rating, the whiter and bluer the light is. Classic, incandescent light bulbs are typically around 2,700-3,000k.


LEDs typically come in a choice of three colour temperatures:

Extra warm 2700k – similar to a classic incandescent light. Used more often in home rather than work settings.

Warm white 3000k – still warm but slightly clearer. Good for cafes and relaxed seating areas.

Cool white 4000k – crisp, bright and white. Good for work and reception areas.

Still not sure? Save Energy 2 Day has lots of experience in tailoring the right light for every situation. When we do an LED lighting installation, we work with you and your organisation to make sure you get the right light fixtures and fittings to suit the needs of your workplace or school.

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