ESL Light Bulbs (That’s Electron Stimulated Luminescence)

by Erik North on January 17, 2012

ESL Light Bulbs (That's Electron Stimulated Luminescence)


I had no idea what ESL light bulbs were either before I started researching CFL alternatives.

And I think they ought to pass a rule where very well-known acronyms are never used for a new thing. Almost no matter how cool your new thing is, it will never escape the original acronym’s gravity. CFL is a very distinct acronym which is now synonymous with the little pigtail bulbs. ESL (English as a Second Language) is not. OK, got that out of my system.

So what is an ESL bulb and how does it fit in the efficient light bulb derby?

What is an ESL Light?

ESL, or electron stimulated luminescence, produces light by firing electrons at a phosphor coating inside the bulb. The resultant reaction produces a strong warm light comparable to the light index of incandescents.

Though ESLs are in their developmental infancy, they have a number of important qualities which could propel their popularity in the post-incandescent era. How do they compare to other bulbs?

ESL Lights – Advantages

An important caveat here is that ESL bulbs have only entered the market in the last two years. CFLs, LEDs, and halogen lights have long track records establishing their performance. ESLs don’t yet have that reliable baseline of real world use. So these comparisons are based mostly on lab testing.

Efficiency: ESL light bulbs are comparably efficient to CFLs, using about 70% less electricity than incandescent. More importantly, ESL lights meet both the 2012 and 2020 federal standards, making them viable from efficiency standards going forward.

Light Quality: ESL light bulbs produce a light very comparable to the warm amber of incandescents. This is one of the major shortcomings of CFLs and LEDs, though their manufacturers have made significant strides in light quality.

Dimming: ESL bulbs, like incandescents, are dimmable across all wattages. There are CFLs engineered to be dimmable, but fluorescent lights perform poorly with dimmer switches. LEDs are fully dimmable.

Temperature: ESL bulbs put out heat comparable to CFLs and significantly less temperature than an incandescent.

Lifetime: ESL bulbs have tested life spans around 6000 hours. This compares to (ballpark) 1000 hours for incandescent bulbs, 10,000 hours for CFLs, and 30-50,000 hours for LEDs.

Chemicals: The big knock on CFL bulbs is their mercury content. CFLs produce light through excited mercury vapor. Each bulb contains between 1 and 5 mg of mercury. Here’s a link to my article on disposing broken CFLs. ESLs don’t contain any regulated materials and can be thrown out in the trash.

ESL Lights – Disadvantages

Durability: ESLs are quite fragile, being structurally the same as incandescents, i.e. a glass bulb.

Price: ESLs have just hit the markets, so economy of scale have yet to curb prices. They are currently selling for $15 a bulb, compared to $0.50 for an incandescent or $1 for a CFL.

Size: This is probably the one drawback unlikely to go away anytime soon. ESL light bulbs are longer, heavier and have a wider base than any other residential bulb. This may make them unusable with some standard sockets.

The ESL light bulbs are part of the next generation of efficient lighting. CFLs have done adequately during the phase out of incandescent bulbs but newer technologies are emerging that will surpass them.

Previous post:

Next post: