Insane, true energy fact of the day

Exit signs are so ubiquitous that they're almost invisible. Every public building has them. In fact, they are so common that, taken together, these little signs consume a surprisingly large amount of energy.

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.

To put this into a bigger context: This is just one small part of what makes buildings, in general, incredibly energy intense. In the United States, we use more energy powering our buildings—from the lights, to the heating, to the stuff we plug into the walls—than we use to do anything else. Because of that (and because of the fact that electricity is mostly made by burning coal or natural gas) buildings produce more greenhouse gas emissions than cars.

Read more about the energy consumption of exit signs and how we can use less energy, while still getting the same services, at Green Building Advisor

Take a look at some stats on energy use in buildings at the Architecture 2030 website

Via Jess McCabe

Image: Exit Sign, a Creative Commons Attribution (2.0) image from mtellin's photostream


  1. yeah, I’ve always thought a photo cell should be used so they only light up whenever its dark around it. 

    Or, you know, glow-in-the-dark paint ffs.

    1. The fire/smoke/carbon monoxide detectors in my house are all wired in. If I had exit signs, I’d want them wired to light upon activation of the alarms, and hooked into the same small battery backup.

      I sure as shooting would not want them on all the time. No reason for that anywhere. 

      1. Except, possibly, in a movie theater or other place where the ambient lighting is normally very low.

        I really don’t mean to sound dickish by pointing out that there are exceptions, especially since we’re talking about an extremely small number of exceptions. And even with movie theater exit signs the traditional ones need to be replaced with an energy-efficient alternative.

        I’ve wondered if it would be possible to wire exit signs to a solar cell. In some cases the signs are placed so deeply within buildings it wouldn’t be feasible, but when the exit leads directly outside–which is often the case with movie theater exits–it doesn’t seem like it would be that difficult to have solar-powered exit signs.

      2. I’d rather notice that my exit sign is broken right when it breaks, rather than not notice until there are flames licking at my heels.

        1. in my house.

          I also check the detection systems regularly the way I should, can’t trust teh power to be on in an emergency and can’t trust lithium ion cells to last as long as they should, so all checked regularly even though there is an alarm for when the system has a power issue. (which is why I know not to trust the ten year battery to last ten years, or even 2!)

          This article caused me to google, I think I prefer radioluminescent if I needed exit signs.

          Also, link contains awesome chart

          1. All our detectors as wired in and battery powered.  I put new batteries in when we moved in, and now they are all seeming to go bad within a short period of each other.  I suppose that seems logical, but the kicker to me is the fact that I can check any of the 9Vs that I pull out and they still show reasonable power output.  I’ve put them in my kitchen scale, multimeter, bathroom scale, ect..  and everything I try them in works fine.

            Makes me almost wonder if the detectors just want the battery changed at a certain interval no matter what.

          2. @ bcsizem – you need to test the battery under load. The voltage drops depending upon how much current is drawn. Maybe your kitchen scales draw much less current than the detector. A good way to test is the measure the battery voltage while it’s connected to the detector – it will be lower than when measured with nothing connected.

        2. emergency lights have test buttons, exit lights could have the same. 

          What we should have on them is occupancy sensors, so they only light up when there is somebody there to see them. And using LED in these is a no brainer as well.

          Offer a tax break incentive to change them over, and you’ll get almost every cheap ass property owner taking the step to do it.

          1. What we should have on them is occupancy sensors, so they only light up when there is somebody there to see them.

            Ever been in a bathroom that has these, but you are in the stall for longer than the programmed delay, and it can’t see you in there, so you have to finish up in the *&^! dark?

            It sucks.

            Imagine that the smoke is starting to get thick, and you know there has to be an exit around here somewhere, but the sensor can’t see through the smoke, so it stays off…

            That’d really suck.

          2. Really folks, these objections are silly.

            Occupancy sensors used to be expensive, today are a cheap component. You make it a replaceable piece, like the light bulb. Its tested regularly when the light is tested. If its failed, its replaced.

            The lights going out while you are on the toilet is a programming question – you don’t design a sensor in an exit light to work the same way as a bathroom. Get it?

            Same with range. And I’d say the sensors would be made to be activated by smoke, not defeated by smoke. 

            High traffic? Look, if the office building is empty at night, at least they go off.

      3. I sure as shooting would not want them on all the time. No reason for that anywhere. 

        Reliability has a higher priority than economy.

      4. exits signs are for more than just a fire.   what if there was a shooting in the place and you didnt know where the exit was?   if the sign wasnt on, you might not know where to go.  ie, movie theater.

    2. >I’ve always thought a photo cell should be used
      >so they only light up whenever its dark

      Adds an unnecessary point of failure to life safety equipment.

      > Or, you know, glow-in-the-dark paint

      Mostly useless unless you have a light shining on it all the time.

      1. I’ll give you a little pass on the point of failure thing, but not on the glowy one.

        If a building loses power or something, there’s a pretty good chance that the lights were on just prior to the dark!  Now, of course you’ll need them on all the time in areas that may not have constant illumination.

  2. One of the more exciting things going on in the energy space is the “smart building” movement. The paybacks are fast, and they make a genuine difference in consumption. Firms like Siemens and Honeywell are big players here.

  3. beware of the ‘every little helps’ efficiency fallacy:

    1. One fallacy of that article is to consider only one “little thing”.

      But there are likely thousands of “little things” constantly at work.  Fix only 40 of those 1/4% energy drains and you’ve got a 10% reduction.

      The tipping point for a lot of economic and energy problems is typically only a few percent.  Consider that the EU’s greenhouse gas reduction goal for 2008-2012 was just  8%.

      The writer’s alternative to “little things”?  “Clean coal” (which will never exist) and more nuclear power plants..

      1. But there are much bigger changes you can do for similar effort. Most of the energy of a building comes from heating and/or cooling it. If you can make your aircon 5% more efficient (or use it 5% less) then it will save more energy than making your exit signs 90% more efficient. All the canvas bags and recycled mousemats and low energy hard drives etc will make no difference if people keep driving cars as much as they do. Fixing the climate is like triaging in war that we are loosing. We need to make huge changes soon.

        I am not saying don’t use the most efficient tech when building a new building. But if you have some sort of budget constraint then think about where you can make the biggest difference. deciding whether to refit an existing building is more complex.

        Have a look at it has an amazing plot of the energy production and use in the UK. It would be nice if they had it measued in CO_2, but never mind, we are talking about efficiency here anyway. Industial electricity is 8.5% of UK energy use, emergency lighting will probably be less than 1% of that. Domestic gas (heating, hot water and cooking) is 25.2% of UK energy usage, so better insulation and smarter thermostats have a big potential. Transport is 55.2% of UK energy use. If you could get people to drive and fly 10% less you make a serious dent to UK emmisions.

        If you think the With out Hot Air book is suggesting we switch to clean coal and nuclear, then you have missed the point of the book. I also hear people cite that book as proof that the UK can manage purely on renewables. I strongly recommend you (and everyone else) read it.

    1. Sadly there is some kind of mental phenomena that makes people use something more if they think it is more efficient. So if they switch to CFLs they are likely to leave the lights on more and so on.

    2. Remember the constant hype about how “Walmart will save the world’s energy crisis” etc. etc.  by pushing CFLs on dimwit American consumers? 

      What about LED adoption? Esp. for applications like Exit signs

      1. That’s what I was thinking, this would be a perfect application for LEDs. Even if theyre dumb, theyre still using a fraction of the energy.

      2. leds have been in use for exit signs for at least 8 years.   i havent sold a new non-led sign in at least that long a period.   that being said, there are still a ton of old signs out there.   the only way i can see anyone changing them is for the following reasons: 1-the sign breaks, 2-they are tired of changing lamps, or 3-they did an energy audit and upgraded the lighting in the building.   if they did the upgrade of lighting, then they would change them.  most likely would get a rebate from the power company too.

      3. What about LED adoption? Esp. for applications like Exit signs

        I consider LED to be the highest quality exit sign, with electoluminescent as the 2nd. place runner up.  I have almost all my buildings switched over to LED. (i’m just waiting for the last of the incan signs to die)

  4. Including “the stuff we plug into the walls” as part of the energy cost of the building is a misleading tactic. 

    It’s like blaming the outdoors for the energy cost of the cars we drive in it.

    1. In most large buildings the exit signs are part of the system, of the building. 

      At least in my experience, I’ve never had to buy them for office space I’ve rented.

    2. Depends. Quite a few items are not built to be used elsewhere so it may as well be summed up with buildings rather than left as their own item on the grand scheme of things.

  5. My crack team of writers is currently working on a snappy one-point-six jigawatts comment to enrich this discussion, I will update you once the project is closer to completion.

  6. The government should offer tax incentives to replace outdated mechanical equipment (RTUs, chillers, boilers, etc).  That would have a much bigger impact than exit signs.

    1. There are lots of govt programs providing incentives and rebates, varies by area, often supported by manufacturers. Keen builders and contractors/remodelers often tap into such resources to (sort of) save the customer money (by upselling)

      1. I’m talking about for commercial grade equipment vs. residential grade.  Think of all of those 25 year old RTUs on the tops of strip malls and fast food joints.

        1. check with the local power company.  i know mine offers rebates.  commercial rebates are bigger than the resi ones.   if varies from place to place.

          1. Agreed that some power companies offer rebates.  Ice storage is a popular one.  I wish there were more incentives, especially from government.

        1. I’m a mechanical engineer and yes it was a real jail.  The “owner” is the regional jail authority that operates the jail (or adult detention centers as they’re now know as).

    1. Unfortunately, due to those pesky laws of thermodynamics, Tritium requires energy to glow too; it just gets all of it ahead of time, instead of drawing continuously.

  7. There are radio active tritium exit signs that require no electricity. Those are the ones that “glow” in the dark. I didn’t even know that some signs contained tritium until I got into collecting radium glass! Many uses for tritium and americium because of the couple hundred year shelf life! Radioactivity hiding in your offices! OooOOOOoo! (Woops! I didn’t see Craig’s post up there!)

  8. I always wonder about this on aircraft; what the hell is the point of having the light up no-smoking signs? They are never, ever turned off. Just have normal notices already, or none at all.

  9. It seems to me that rather than pointing at exit signs in particular (which are obviously a sensitive topic because of their life-saving role), this can be summed up in a much simpler trope: we need to end our reliance on incandescent lighting. Another interesting avenue to explore in that regard is that fact that the planet is running out of Tungsten (the metal used to make light-bulb filaments). Tungsten is a very useful metal because of its incredibly high melting point, and we’re exhausting our supply thanks to a century of making disposable, short-lived light sources which are not readily recyclable. 

  10. I’m surprised this hasn’t been mentioned, but Exit signs have several federal (I believe) regulations about what types of bulbs can and can’t be used.  Just because you could screw in an LED replacement doesn’t mean it’d pass code (not unless the bulb was certified for the fixture so to speak).  So you still end up with a lot of older signs using incandescent bulbs, and wasting more electricity.  Obviously the new signs are LED and much more efficient, but I guess that’s the compromise between technological progress and safety. 

  11. Since there seems to be interest, I’ll spell out a few minor points (Relevant to buildings in USA only)

    Private parties don’t buy lighted exit signs when they move from place to place. They are installed when the building goes up, normally by the electrician, and they stay there ’till they or the building dies.

    They do not switch off, public buildings have people doing stuff in them at various days and hours, not just 9-5 If you add a switch you add a point of failure.

    In some cities they may even be required to be on their own circuit, seperate from all other electrical loads in the building.

    There are EXTREMELY tight codes around the construction of the signs. Getting one approved for sale to the public is a long and arduous proccess. If you change something, even going from say, phillips head fasteners to hex head fasteners, you have to go all the way through the entire proccess to get them recertified all over again.

    Sensible manufacturers respond to this by changing designs as infrequently as possible. It’s just not worth the pain.

    Old school incandesent signs are popular because the initial purchase price is very low, which means that when someone is bidding to do the signs, they use incans in the bid so their quote will be lower and they will get the work, not some guy who specs high priced 25 year fixtures.

    Nobody but the building operator cares about operating and maintenance costs. They are they are either not around when the building goes up, or they are squeeezing the contractors to trim just a little more out of the budget. They contractors do as they are asked, and the building gets signs that were state of the art in 1965.

    The Tritium signs are normally used when it would be excessive to have an electrician run power to some distant location, just to run a sign. They meet code but are pretty dim, cost probably $200-300 per unit, you have to register them with the feds when you put one in, and you have to pay someone else to take them for disposal, it’s probably a felony to just toss a dead one in the dumpster.

    They do have an advantage that they require nothing at all from the building, not power, not light, not maintenance, no resticted temperatures, nothing.

    The reason the feds are fussy about them is that when Tritium gets out of the tubes down at the landfill it combines with any passing Oxygen and becomes tritiated water, which can be breathed or drunk without you even knowing it. This is not recommended. Rumor has it that the Japanese have had problems with this, but I haven’t worked there, so I don’t know.

    1. The contractor has to provide what the engineer specifies.  And a good engineer wouldn’t specify cheap ass exit signs realizing the cost savings of reduced maintenance costs.

      1. The architect may specify a high end sign, but ultimately the owner’s budget dictates what gets used.   that being said, incandescent signs aren’t even sold anymore.  i’ve had led exits as standard items for at least 8 years. 

  12. You know, reforming Exit lights would be good, but reforming the way we build buildings would be better. Incentivizing retrofits to older buildings would be even better.

    One of the programs of the recent recovery efforts was low interest loans to do energy retrofits for older homes. It was a great opportunity. However it was limited in several ways – if you already had a second mortgage on your home, guess what – you could not participate in the program. Guess who have second mortgages on their homes, lines of credit or otherwise? The very people that would benefit most from energy retrofits. Programs like this have to be carefully designed, or they don’t help the people that need it most.

    1. the financing aspect is the one area that is missing in the equation.   we do energy audits, show the customer that they will get a payback in 2 years with the power company kicking in a rebate to pay for a big portion of the job.  but the job never goes anywhere because they don’t have the cash to outlay.     I am talking commercial jobs, not residential.  

      1. I think you are right. If you want it to happen, you structure the program so people can do it with no money down, and the energy savings pay the cost over a reasonable period of time. Then its a no brainer and everybody does it. But it also means it is almost sure to not be a profitable loan for the financier, which is why the government has to be the one to make it happen.

  13. the power company rebates are fueled by the governement.  so, in essence, the govt is providing it.  but i get what you are saying.   

    1. I thought the power companies did that on their own with the thought that it’s cheaper to offer incentives and reduce demand than to build a new power plant.  Same reasoning for ice storage – shift demand to off-peak hours.

  14. Here is the story I’d really like to tell to people here reading about energy efficiency in building. The way we build houses here in the US is crap. We do basically the same thing we did in the 1950s, maybe we are putting a little bit more insulation in today, maybe the wall is a little bit thicker. But its not like the energy performance of our houses grew at the same rate as energy cost did. 

    So in the 70s we had ourselves a little oil crisis, anybody old enough to remember that? The shock of waiting in gas lines, buying gas on even and odd days? We panicked for a few years, Jimmy Carter put solar panels on the white house, then we went back to building houses the way we always did. Crappy.

    We were not the only place that had an oil crisis then – most of the developed world did. If we look at Sweden, the got slammed too. But they didn’t have their own oil resources (like Norway for instance). When it was over they did not go back to same old same old. Instead, they completely re-invented the way that they build houses. Today their houses outperform ours by a wide margin – it is embarrassing.

    Sweden is interesting because like the US, they build wood houses. Most of the rest of the EU its not so – masonry houses are more common. But Sweden has a sizable timber resource (side bar: much better managed than ours) and so they build wood houses – just like we do. In fact up until the 70s oil crisis the US and Sweden built houses in just about the same way. But not today – Sweden spent 40 years improving the wood house, and today they make housing in the US look like an amateur show.

    So here’s the thing. Sweden has done all the heavy lifting here. All the hard choices about how to build better performance economically have been made, they’ve broken all the new ground. Its all there for the taking. And in fact in the 1980s was all laid at the feet of the US Housing industry – HERE IS HOW ITS DONE. A ground breaking research project by the late Lee Shipper, and Henry Kelly parsed all this and documented the revolution in Sweden, and delivered it here in a detailed report, and companion book COMING IN FROM THE COLD. These were brilliant researchers who went on to have stellar careers doing important work in Energy. Look them up if you doubt me. I wrote about this here:

    What did the American Housing Industry do? Abso-fucking-lutely nothing. Buy a new house today and you’ll get 4″ of lousy insulation, maybe a few inches more if you are spending. Its really hard to believe the story that America leads the world in technology, when something as ubiquitous as home building is done in such a profoundly incompetent manner, and its born out by our national energy bill. Yeah, we need to fix Exit lights, but the first thing we need to fix is to get over ourselves and start working on this in earnest.

  15. I was told by an OSHA rep that any new signs that need to be installed should also include green signs, and closer to ground level, since a sign above the door is the first thing to get covered up by smoke.

  16. 350 watt per exit sign? that seems awfully high. I suspect the average is closer to 50, and going down as incandescents are being replaced.

  17. Check this out – if everything that has a switch that says “off” really turned off when you flipped that switch, the Texas cartel would have had to shut down an entire extra power plant to create California’s fake energy crisis.

    It’s true!

  18. “In the United States, we use more energy powering our buildings—from the lights, to the heating, to the stuff we plug into the walls—than we use to do anything else. ”

    False. We use more energy moving water from where nature put it to where we use it. In California, 57% of all energy is consumed pumping water.

    1. Weeeeellllll… here in my building, the energy I use to pump water is part of the cost of “powering my building”.     How exactly is providing water different from providing light or TV?  I use electricity to do all three, and since I only need to pump it up about 25 feet it takes less power than my furnace blower.

      PS:  California is not equal to the United States.  Just sayin’.

  19. I was just at Burning Man where lots of people spent hundreds or thousands of dollars to power their projects from solar panels rather than spending tens of dollars on batteries.  These are the same people who would spend hundreds of dollars on a new exit sign to save tens of dollars in electricity costs.

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