What is More Energy Efficient – LED, CFL, ESL, Incandescent, or Halogen?

In my quest to make my home as cost-effectively efficient as possible, I’ve spent a lot of time researching and trying different lighting solutions.

My first step was to use lights less often, my next step was to question how much light I really needed (i.e. do I really need a 100 watt bulbs, or is a 60 watt bulb enough?), and the last step was to replace bulbs with more efficient ones, which is a continual process.

You're probably thinking that LED is the clear-cut winner in the efficiency war.  Well, you may be surprised to find out this may not be the case today!

Deciphering Marketing and Potential from Reality

For generations consumers have become familiar with incandescent lighting.  We all have a general feel for how much light a 25w, 60w, 75w, and 100w bulb produce.

When Compact Fluorescent (CFL) bulbs hit the market, the makers smartly identified their bulbs based on a rough equivalency to incandescents (i.e. “60 watt equivalent”).  That is helpful to the average consumer looking to get a rough idea of the brightness of a bulb.

However, the real measure of brightness is lumens, not the wattage of a bulb.  This is important to note because any manufacturer can claim “60 watt equivalent”, but the reality may be that their bulb produces much more or much less light output.  The lumens rating will help decipher this.

 
A simple metric to determine the most energy efficient bulb is to determine the lumens produced per watts (LPW) consumed (i.e. lumens divided by watts).

Common knowledge says LEDs are the most efficient lighting available, and CFLs are much better than incandescent.  And what the heck is that ESL I mentioned in the title, anyway?  (Read here for more about the Vu1 ESL technology).

Let’s take a look at some comparative analysis based on a selection of bulbs on or entering the market today.  Note that I picked a handful of bulbs as examples, so the LPW ranges may vary a bit more than shown if all bulbs were to be considered.
 

Incandescent: 11 - 18 LPW

Halogen: 12 -  24 LPW

LED: 45 – 70 LPW*

CFL: 40 – 70 LPW

ESL: approx 31 LPW

*To get optimal LED performance, color temperature must be cooler than typical 'soft white'.

As can be seen, CFL is comparable to LED.  In fact, in many cases the LPW is better in CFL when comparing “warm” color temperature bulbs.

Power Factor

When reading bulb spec sheets, you may occasionally notice a “power factor” rating, which typically looks like this:

Incandescent: 1

LED: .80

CFL: .52

ESL: .99
 

Power factor is the measure of real power to apparent power.  Without going into the theory, devices with a worse power factor draw more current and tax power distribution systems more than those with a high power factor.  Thus, utilities require more infrastructure to support low power factor devices such as CFLs.

So, from a utilities perspective, the “power factor” adjusted LPW looks more like this:

Incandescent: 11 – 18 LPW

LED: 36 – 56 LPW

CFL: 20.8 – 36.4 LPW

ESL: approx 31 LPW

From an electric utility perspective, suddenly LEDs look a whole lot better, and ESLs seem viable (especially for a new entry…remember, LEDs have been being developed for a decade now).

The Future of Lighting Efficiency

We've seen CFLs make rapid strides in price and quality, but they still require toxic mercury, and still don't have the capability to turn on instantly at full brightness (though they have gotten better). These issues are insurmountable, in my opinion, and it is probably safe to say that CFLs are ultimately a 'bridge technology' that will disappear over the next decade.

LEDs have much more long term potential than CFLs. Price (and especially price of 'soft white' 2700 K color temperature bulbs) is the biggest hurdle. It is expected that LED efficiency will improve by as much as 50% over the next couple of years, making them the clear-cut LPW winner. LEDs still have some limits when operating in hot environments, which must be overcome. But if price can come down in the important soft white category, then LEDs are well positioned.

ESL is a bit of a wild card, being a unique technology. VU1 is hoping to seize a small window of opportunity, providing a quality of light equal to incandescent, at a price much better than LED, while providing solid efficiency, if not top of the line, efficiency.