Should You Pay Attention To Lumens Or Watts?

Halogen, CFL, LED light bulbs

Before the passage of the 2007 Energy Bill, it was easy to replace a general service household light bulb. All you had to do was read the number on the top of the bulb and find the exact replacement: 60 watts was always 60 watts.

But now, with common 40, 60, 75 and 100 watt incandescent bulbs no longer being manufactured for general purposes, consumers are being forced to change their thinking on lighting. This is one reason many manufacturers publish a Lighting Facts label for many new bulbs: to indicate to buyers what they are getting and how it compares to the light bulbs they always purchased previously.

Watts was a useful way to measure the relative light output of incandescent bulbs. It’s easy to remember that a 60 watt bulb is brighter than a 40 watt bulb, but dimmer than a 100 watt bulb. And when almost all the bulbs were incandescent, it was really easy to know what you were getting.

The problem is that watts is a measure of energy used, rather than light output. So a 60 watt incandescent is equivalent to a 43W halogen, a 14W compact fluorescent, and a 10W LED. But good luck remembering that on your way to the home improvement store when you’ve already thrown away the burnt-out bulb!

This is a big reason why lumens has become the new watts. Lumens is a quantitive measure of the light output or brightness of a bulb. Because of the relative efficiency of LED and CFL bulbs, an incandescent may output 800 lumens at 60 watts, a CFL generates the same 800 lumens at 13 watts and an LED at only 10 watts.

In addition to light output, a light bulb’s rated life is now something consumers should take into account when buying the new generation of bulbs. Incandescent bulbs typically last around 1000 hours.  Compare that to CFLs at 10,000 hours and LEDs at 25,000 hours. Of course CFLs and LEDs cost more than incandescent. But, when you realize you will have to buy 25 incandescent bulbs versus one LED, the higher cost of the LED looks a lot better, especially if you include the money saved on energy costs. In addition, the usual three- to five-year manufacturer warranties on LEDs can make the transition smoother.

When incandescent bulbs were ubiquitous in homes, watts was the best way to measure relative brightness. Whole generations raised on watts, though, will have to change the way they think about lighting, especially as common incandescent bulbs become harder to find. Likely, in a few years, the outcry over the “light bulb ban” will die down, as consumers get used to thinking in lumens and looking for the Lighting Facts label.

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Nick Heeringa

Nick is a writer, publisher and editor for the Topbulb blog. Check back often for more of his writing on lighting applications and announcements for the Topbulb website and blog!