Blog Post

Saving a Little More Energy With Exit Signs

Those ubiquitous exit signs use a huge amount of electricity; a little-known alternative to conventional LED products offers surprising savings.

An exit sign at Yale's LEED-Platinum Kroon Hall. Click to enlarge.Photo Credit: Alex Wilson

In the years that I’ve been writing about energy and energy conservation (longer than I really want to admit), I’ve reported on several dramatic transitions in how we illuminate the exit signs in commercial buildings. For an energy geek, it’s been an exciting technology to watch.

Why care about exit signs?

Why do we even pay attention to exit signs—those ubiquitous red or green illuminated signs that direct our escape from a building should the need arise? They can’t use very much energy, can they?

Each one uses relatively little electricity, but they are on all the time. And we have a lot of them in our schools, factories, and office buildings. The U.S. Environmental Protection Agency estimates that there are more than 100 million exit signs in use today in the U.S., consuming 30–35 billion kilowatt-hours (kWh) of electricity annually.

That’s the output of five or six 1,000 MW power plants, and it costs us $2-3 billion per year. Individual buildings may have thousands of exit signs in operation.

From incandescent to fluorescent to LED

When I first wrote about exit signs, the vast majority of them were illuminated with two 15- or 20-watt incandescent lamps. These lamps often lasted less than a year, and an exit sign with two of these lamps used nearly as much electricity per year as an Energy Star refrigerator uses today. For businesses, the labor cost of replacing those incandescent bulbs could be nearly as expensive as the electricity they consumed.


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Thus, there was a lot of excitement in the early 1980s when compact fluorescent lamps (CFLs) made their way into exit signs. One or two CFLs using a total of 10–15 watts replaced up to 40 watts of incandescent lighting, and they lasted several times as long. The low power factor of these CFLs actually reduced the energy benefit for utility companies (a complex issue that I won’t bore you with), but end-users saved a lot of money. The biggest downside was the small amount of mercury in each CFL.

CFL lighting for exit signs didn’t last long, however. By the early 1990s, LED technology emerged for exit signs. LEDs are solid-state lighting devices that use relatively little electricity, do not require mercury (as is required in fluorescent lamps), and last a very long time. Early LEDs were usually red or green (think of those indicator lights on your stereo equipment), which worked fine in exit signs. (White LED lighting for general illumination is a lot more challenging.)

The first LED exit signs dropped the electricity use down to 5–7 watts, and there are LED exit signs on the market today that use as little as 1.8 watts and still meet the emergency egress standards of building codes.

Energy efficiency regulations gave a huge boost to LED exit signs. A revision of the Energy Policy Act of 2005 set a maximum electricity consumption of exit signs at 5 watts (effective in January 2006), which effectively eliminated both incandescent and CFL exit signs.

With such low electricity consumption, LED exit signs can be coupled with relatively small battery back-up systems—a requirement (and significant environmental impact) for most exit signs.

Just as significant for bottom-line-conscious businesses is the very long life of LEDs. Most are rated at 50,000 hours—many times as long as incandescent lamps. The power factor is also better than that of CFL exit signs, which makes utility companies happy.

Enter electroluminescent exit signs

There isn’t a lot of additional gain to be squeezed out of a 2-watt LED exit sign, but there is some. A quite different technology allows fully compliant exit signs to be powered with less than a fifth of a watt—at least a ten-fold drop compared with most LED products.

Electroluminescent or light-emitting capacitor (LEC) technology produces a uniform layer of light rather than discrete point sources (as with LEDs). Limelite Technologies, the leading manufacturer of electroluminescent exit signs, describes how the technology works on its website.

Again, the savings from each one isn’t that great, but spread over tens of millions of products, the savings could be very significant.

Exit signs in our GreenSpec Directory

In our GreenSpec product database, we briefly listed CFL exit signs, then included dozens of manufacturers of LED exit signs. Today we list just two products: LimeLite of Maxwell, Texas (also at, which produces the Series 16 and Design Select exit signs, consuming just 0.18 watts each; and Greentorch (also at, which makes a wide range of LED exit signs including an LEC model using 0.25 watts and having an expected life of 30 years.

Our detailed criteria for exit signs are described here.

Exit signs to avoid

While there is a lot of good stuff in the exit sign world, there are some products to watch out for. One of them is “zero-energy” photoluminescent exit signs, which harvest ambient light from the space and will deliver needed emergency exit sign illumination for up to a couple hours during a power outage. These use glow-in-the-dark materials that are familiar in toys.

The problem is that code requires fluorescent lights to shine on these photoluminescent exit signs so that they will be fully charged and ready to provide that emergency illumination during a power outage. You will use more energy for the fluorescent light source to charge the exit sign than a standard LED exit sign will use to operate. Yes, the battery can be eliminated, but that still doesn’t justify the additional electricity use (in most cases).

The other product I like to stay away from is radioluminescent, or tritium-powered, exit signs. Tritium, a radioactive isotope of hydrogen, provides the illumination. While tritium emits fairly low-energy beta particles that aren’t strong enough to penetrate our skin, if we breathe in tritium gas or swallow tritiated water, the radiation can damage cells in our body. It’s a product I’d rather keep away from.

A detailed summary of exit sign technologies, including discussion of why photoluminescent products don’t make sense, is available in our EBN feature article on the evolution of exit signs.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

Published August 29, 2012

(2012, August 29). Saving a Little More Energy With Exit Signs. Retrieved from

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September 14, 2012 - 1:48 pm

Thank you for your response, Nadav. I did go to the article Alex mentions. The article was based on a report by the National Electrical Manufacturer's Association (who have a significant amount at stake by the success of exit signs that require no electricity yet perform with greater reliability than the signs their members manufacture). Please consider the source. I have done site evaluations in hundreds of facilities with a light meter in hand. I do agree that these signs do not work in all buildings, nor do they work in all parts of all buildings. But in most buildings I have reviewed, they meet code without "carefully directing light". Lighting shines in a parabolic shape and the lower levels of an egress corridor is always brighter than the higher levels. Thus, low level installation is almost never a problem. Dark corridors and canned light do create challenges whereby photoluminescent exit signs may not work in all situations. But most  facility engineers understand and embrace their ability to save energy, require no maintenance or testing. And they appreciate that they do not have the liability of having signs that are not operating as they should because of failing batteries or components. Government, schools, hospitals, and companies large and small are adopting this techonology because it makes sense. Before discounting it. check the light levels in your facility. Give us a call and discuss your needs so you can see how this would work in your facility. To abandon a green technology because NEMA wrote an article to protect their members from losing business is a tragedy. Especially on a site such as one dedicated to building green.

There are also other new innovative photoluminescent applications, such as emergency lighting, interior/exterior path markers, and emergency generator restart systems. Do check them out. I think you'll be impressed!

September 14, 2012 - 6:16 am

If that's true that the LEC products are not UL-listed we should reconsider listing them in GreenSpec. We'll take a look at that. 

Regarding the photoluminescent signs, however, take a look at the more in-depth article that Alex references in this story for more details on the problems with shining enough light on the signs to keep them charged. To meet modern energy codes for lighting power density in hallways light needs to be directed carefully, and directing some of it to shine on an exit sign is counterproductive. 

September 10, 2012 - 6:34 pm

My company is Safe Glow Corporation and we manufacture a top performing line of photoluminescent exit signs in the U.S. I can assure you that photoluminescent signs do meet both the NFPA Life Safety 101 building codes and the International Building Codes. In Fact, our signs are International Code Council Evaluation Service Certified to meet the 2009 International Building Codes worldwide. In addition, they do not require that lighting be on 24 hours per day unless your building is occupied 24 hours per day. IBC 2009 verbiage states that lighting is only required when the building is occupied. Some codes may require lighting of egress stairwells 1 hour prior to building occupancy, but this is to charge the stair step covers and stairwell landing low-level path markers which are also code required. 

In your article, you recommend using LEC signs because they only use 1/4 watt. Currently, there is no product on the market from either manufacturer you list that offers a UL listed LEC exit sign. The 2009 International Building Codes states: "1011.4 Internally illuminated exit signs. Electrically powered, self-luminous and photoluminescent exit signs shall be listed and labeled in accordance with UL 924 and shall be installed in accordance with the manufacturer’s instructions and Chapter 27." This means that all exit signs require a UL or ETL listing. Safety needs to come before energy efficiency.

Want to learn more about why photoluminescent is a better option for emergency egress? Read Amanda Ripley's "The Unthinkable" and you'll understand more about why a product that can glow for many hours longer than battery backed exit signs are gaining such a following. 

By using 3D modeling, those building energy efficient buildings can ensure there is sufficient lighting with existing light just by placing the fixtures properly. Photoluminescent signs allow you to build without conduit, wiring, junction boxes, circuit breakers and cover plates, not to mention skilled electrical labor. You'll save $450 per exit sign for every exit sign you choose photoluminescent over elecrical with battery back up. Once your building is built, you will save even more. For every sign you choose photoluminescent over LED, you'll save $50 per year per sign for the life of the sign. This represents savings in electricity, replacement batteries and parts, maintenance and testing. Photoluminescent signs do not require any of this. If you want to save the environment, eliminate Ni-cad batteries being used in electrical exit signs. Cadmium poisons our water supply, and less than 7% of these exit signs batteries are being recycled as required. They are all ending up in our landfills as toxic time bombs for future generations. Take another look at photoluminescent exit signs. They make a safer and greener alternative than touted in the above article. 

September 14, 2012 - 8:34 am

The most the energy codes let an exit sign use is 5W.  Most are less than this.  5W * 24hours * 365days / 1000 * $0.12 = $5.25 per exit sign per year.

And per my previous post the Building Code requires exit signs to be illuminated at all times.

The limelite product said it is ETL listed and meets UL924 standards.  Don't just make up stuff to sell your own product.

September 6, 2012 - 11:43 am

I finally heard back from one of the conglomerate lighting manufacturers.  They said they tried using this technology over 30 years ago and had to abandon it because of reliability concerns.

- After a few years the light output would be noticeably less.

- The technology hates moisture.  Any humidity or dampness and it just lowered the light output that much faster.

- No warranty is mentioned in their literature.  I've sent them a message asking about this.

  ----- Yeap, no warranty

And it sounds like "electroluminescent" is the common term used for this technology.

September 4, 2012 - 11:15 am

Hi Bill!

Apologies about the terminology: I was using ELM as an abbreviation for "electroluminescent" as I thought it would go well against PLM for photoluminescent.

I agree that LEC is the technically correct term for what I called ELM but would beg to differ with your statement that LEC and LED are similar species. Yes, they are both "electroluminescent" in that they produce light from electricity - but on that criterion you would have to lump them in with incandescent bulbs and CFLs - and I'm sure that's not what you intended.

LEDs are current-based devices while LECs are voltage-based; and while we are at it, in this particular context there is the question of whether exit signs would use green LEDs or white LEDs behind a green filter. Why? Because green LEDs produce green light directly, whereas "white" LEDs typically produce a light which more or less approximates to white by shining a blue LED (only fairly recently available in commercial quantities) on to a yellow phosphor, so they are actually akin to PLM lighting, except that they are continuously powered.

Incidentally, I first came across electroluminescent panels almost 50 years ago, when I was at college. Their attraction for signage is that they can easily be fabricated in the form of letters and numbers, provided electrical continuity is assured in a similar way to making stencils. However, they have never been "mainstream" because the only color obtainable (so far?) is some shade of lime green.

September 4, 2012 - 11:51 am

Green LED's are simple and cheaper to make then white LED's so any green exit sign is straight green LED light.

I always compared white LED technology to fluorescent.  Taking UV/blue light and passing it thru a phosphor to convert it to visible light.  No storage of energy.

PLM is a bit different.  More like the glow in the dark stars I put on my kids' ceiling.  It stores energy.

I think the Limelite company just liked using the "electroluminescent" term to sound impressive.

September 5, 2012 - 6:02 am


I agree about LED exit lights being most likely to be green LEDs and with your comparison of white LEDs to fluorescents. However, PLM is really the same - it's just that fluorescents and white LEDs use phosphors that give a high light output with short remanence, while PLM uses low output phosphors with a very long remanence.

I'm not sure that all the "glow in the dark" stars are the same though, as I am sure that some I have seen have been "Betalights" - that is: powered by mildly radioactive material rather than the highly radioactive radium which was used in WWII for aviators' luminous watches.

As for Limelite, they are just using the term which, as I mentioned, has been used for this type of light for the last 50 years and more.

September 4, 2012 - 10:27 am

Why do you keep on about PLM signs, Richard?

Because Alex wrote this:  And he's wrong when he writes it.

Exit signs to avoid

The problem is that code requires fluorescent lights to shine on these photoluminescent exit signs so that they will be fully charged and ready to provide that emergency illumination during a power outage.

September 4, 2012 - 10:22 am

Why do you keep on about PLM signs, Richard?

To quote from Alex's article re ELM signs:

"A quite different technology allows fully compliant exit signs to be powered with less than a fifth of a watt—at least a ten-fold drop compared with most LED products."

Please note the "fully compliant". If these signs ARE fully compliant, I repeat that someone should make the comparison between ELM and LED.

Of course, LED lighting is presently "the best thing since sliced bread", and I imagine that the LED lighting manufacturers would very much like to direct attention away from ELM lighting, as it is (I believe) very much simpler and cheaper to produce, and hence likely to generate very much less profit per unit than an LED system with its associated transformer (or equivalent) and hefty heat dissipation finned casing.

September 4, 2012 - 10:55 am

Tony, LED's are electroluminescent technology.  This product is just a different kind of electroluminescent technology.  Instead of diodes it uses capacitors.  So it's more of a LEC vs LED technology.  Not ELM.

September 4, 2012 - 10:07 am

I was refering to the comments about PLM signs. To my knowledge electroluminescent havn't met the Ul standard for EXIT sign (egress sign) performance,...
PLM exit signs, hwoever do.
His confusion about the requirement for a lighting source on the EXIT signs, to "power" the PLM signs is what I'm correcting.
Most building and fire codes require that hallways and especially egress areas in hallways must be lit to a minimum level 24/7. Those lights are sufficient to power PLM EXIT signs. No additional lighting on the sign is required.
PLM EXIT signs must be seen from their certified distance 90 minutes after a black out, and are tested for this after being powered for only 1 hour at 5 foot candle (54 lux). (In Canada the requirement is 2 hours of operation after the same powering). Most signs are above doors and recieve more than 54 lux of light from the hallway lighting, and especially because the EXIT door has a specific lighting level required. (Usually 10 foot candles). Being powered 24/7 means these signs will operate well past the required 90 minutes or 2 hours.
They meet codes. And although they don't save tons of enrgy versus LEDs they have no maintenance or replacement cycle. Thats green.

September 4, 2012 - 10:44 am

Richard,  I think you're confused about 2 things relating to Code.

1) Egress lighting does not need to be on 24/7.  Section 1006.1 "The means of egress ... shall be illuminated at all times the building space served by the means of egress is occupied."  So any time the building is unoccupied then the egress lights can be turned off.  And most of us have energy codes now where night lights on 24/7 in hallways of unoccupied buildings is a no no.

2) 1011.4 "... Exit signs shall be illuminated at all times."  So a PLM exit sign needs a dedicated light to shine on it at all times, and any other light source is going to consume more Watts then an LED sign.  If it only relied on the ambient light to charge, what if power went out 10 minutes after people showed up in the morning.  The PLM sign wouldn't have enough charge to last 90 minutes at the required output.

The product information for the Limelite exit sign says it is Listed and meets UL and Life Safety Code requirements.

September 6, 2012 - 11:53 am

Which code are you quoting. There are over 1300 AWJ in North America and the codes that apply change.

Having said that, the section you quote refers to buildings that have controlled access. Where it can be guaanteed that the building isn't occupied. The hundreds of exceptions to this  include hotels, apartment high rises, and most public buildings

One of the misconceptions about PLM is that it has a limited operating period. Most PLM signs that meet the UL standard, when fully powered, will glow visibly for us much as 48 hours. How long is the building unoccupied? As well, most PLM EXIT signs, powered at 100 lux for 10 minutes, will provide 90 minutes of visibility in the event of an emergency right after the building has been reoccupied. (The certification is at half the usual required level of light)

I don't think its a huge selling point for powered signs to say that when the building is unoccupied we will continue to be powered and glowing. I mean, who's that for? Its counter to the purpose of powering down the lights.... and isn't providing safety for occupants. There being none... And when the building becomes reoccupied, isn`t the power turned back onÉ

Having said that codes and standards do have to be modernized to allow for energy saving, and material saving and life extension (the key benefit of PLM)  and at the same time ensure safe conditions. In Ontario Canada a recent law allows for the use of motion detectors in common areas of buildings, like apartments, as long as the egress areas remain lit. That allows for power use savings as much as 95% in little used areas. At the same time it ensrures that should motion detectors fail, or fail to come on in a black out, the egress areas can still be seen by people entering the common area (hall).

It is in the interests of powered sign manufacturers to maintain confusion over codes and maintain misperceptions about new technologies.

September 4, 2012 - 9:40 am


I'm not sure whether you were responding to my comment or Alex's article.

Alex specifically warned against photoluminescent signs for the same reasons you state, while my comment related to ELECTROluminescent lighting, which is a completely different animal.

Somebody may be able to make a worthwhile comparison between electroluminescent and LED signs on the basis of power consumption and lifetime.

September 1, 2012 - 4:02 am

For some time now I have used a GE electroluminescent light in the bedroom as a nightlight - the blurb gives the consumption as picowatts, translated as cents/year.

In is good to note that this type of lighting can comply with Code requirements for illumination level for Exit signs - I will notify my Electrical colleagues, for them to follow up on new projects.

However, I would like to suggest the use of this type of lighting to follow the line of the handrails in escape stairs. This is mentioned in Codes but I do not recall the exact provisions. The point is that lighting in such stairways is usually either on 24/7, in which case it uses a LOT of energy, or, if someone is trying to earn LEED points for saving energy, is controlled by motion sensors (because it is unreasonable to ask someone escaping from a fire to hunt for a light switch on entering a dark staircase!).

Providing EL lighting along the handrail 24/7 would use very little power and would lead escapees directly to what they need to hold onto in order to get down the stairs safely in a hurry.

September 4, 2012 - 9:19 am

Your comments about photloluminescent signs are misinformed. when you say this

The problem is that code requires fluorescent lights to shine on these photoluminescent exit signs so that they will be fully charged and ready to provide that emergency illumination during a power outage. You will use more energy for the fluorescent light source to charge the exit sign than a standard LED exit sign will use to operate. Yes, the battery can be eliminated, but that still doesn’t justify the additional electricity use (in most cases).

The light shining on photlouminescent signs are the lights that also light the egress area and hallway. In most public access buildings this is required by code 24/7. There is no special light or additional light required. And yes, although there isn't a lot of energy saved by eliminating LED lights for PLM, however the biggest saving is in maintenance costs. The life of PLM signs, without any maintenance, is over 35 years. How many LED replacements will you make in that time?

August 30, 2012 - 11:56 am

Alex, fantastic article! We need to realize, as we strive for net-zero energy buildings, that every little bit counts! As I read about the move to LEC exit signs, I also thought about the impact of Power over Ethernet (PoE) security systems, cameras and telephones. These items have moved to drastically lower energy consumption over legacy products, and are also being specified in the most energy efficient buildings!