What are Lumens?
It’s important to find the right brightness for your space. Too bright and the room will feel surgical and cold. Too dull and the room won’t be suitable for reading or working.
With older light technologies, brightness was the same as wattage. If you wanted a brighter light bulb, you simply upped the wattage.
But with new lighting technologies, like LED, this isn’t the case. It’s now possible to have a much brighter light, without increasing the energy used. This means that the wattage might be lower, but you’ll still get the light quality you’re hoping for.
To enable comparisons between new and old lighting options, we now use ‘Lumens’. But what are lumens and how are they different to simple wattage? In this article, we’ll explain how to buy light bulbs based on lumens, and why it’ll save you money in the long-term.
Definition of lumens
The Collins English Dictionary says that a lumen is ‘the derived SI unit of luminous flux; the flux emitted in a solid angle of 1 steradian by a point source having a uniform intensity of 1 candela’.
Our jargon-free definition is that a lumen measures the amount of light produced over a period of time. The greater the lumens, the brighter the light.
What is luminous efficacy?
LEDs are dramatically better at turning electricity into lumens. Whereas an incandescent bulb would need 40 watts of energy to produce 400 lumens, an LED needs just 7.
Therefore, a LED light bulb has more ‘luminous efficacy’ as it converts watts to lumens much more efficiently. This is typically measured in lumens per watt or lm/w.
Check out the table below for more examples:
|Lumens||Incandescent Wattage||CFL Wattage||LED Wattage|
|400-500||40W||8 - 12W||6 - 7W|
|650-800||60W||13 - 18W||7 - 10W|
|1000-1400||75W||18 - 22W||12 - 13W|
|1450-1700||100W||23 - 30W||14 - 20W|
|2700+||150W||30 - 55W||25 - 28W|
Compact Fluorescent Lamp bulbs (CFLs) have a better luminous efficiency than incandescent bulbs, but are still not as efficient as LEDs.
How to buy LED light bulbs based on lumens
To help consumers and professionals make more energy-efficient choices, the Energy Independence and Security Act introduced a “lighting facts” label. This helps you to buy bulbs based upon actual performance, rather than wattage.
On a lightning facts label, you'll find:
- Brightness - Remember: the higher the lumens, the brighter the light.
- Estimated Yearly Energy Cost - How much it will cost to run the bulb.
- Life - How long the bulb should last in typical conditions.
- Light Appearance - The color of the light from the bulb, expressed in Kelvin. This is known as the Correlated Color Temperature or CCT. The higher the Kelvin rating, the cooler the light emitted.
- Energy Usage - The lower the watts, the lower the energy usage.
A quick note on light appearance: CCT does not give any information about the color rendering ability of the LED. You'll want to look at the Color Rendering Index (CRI) instead. This is a measurement of how accurately a light source picks up on the color of objects, compared to an ideal or natural lighting source. Walls, artwork and furniture may look different colors in some lights, because of the CRI.
Why are lumens important?
Selecting your bulbs based on lumens, rather than watts, brings a number of benefits:
- Energy and Cost Savings: The US Department of Energy believes that huge energy savings can be made by switching to LEDs, cutting business and homeowner electricity bills by $50 billion a year.
- Ecological Impact: Bulbs with improved luminous efficacy last longer, as less energy is turned into heat. A longer-lasting light bulb means less manufacturing is required, reducing carbon emissions and material usage.
If you’re looking to switch to more efficient LED lighting in your home or business, take a look at our online shop or head over to our blog for more information.