CFL vs LED: The energy saving light bulb debate is over
Submitted by Jolene Hermanson and Rebecca Zisser on | Updated Wed, 25/10/2017 - 16:16
One of your bulbs just broke or burned out. You want to get an energy saving light bulb but which type lasts the longest all while giving you the best quality light? And more importantly, which will put the most money back in your wallet? Choosing an energy efficient light bulb is a lot easier now because the old CFL vs LED debate is over.
LEDs are better than all other types of light bulbs because they:
Last the longest
Produce great quality light
Save you the most money
If these bulbs are the best then they must be pricey right?
For $2-$4 you can find a wide range of LEDs, so it’s much easier to upgrade your lighting.
Before LEDs used to cost $20 or more each. The bulbs would pay for themselves eventually by cutting your electricity bill but for most people they were just too expensive to try out.
Now that they cost almost the same as CFLs, it's a great time to make the switch. In fact, with LED bulb prices so low they will pay for themselves in a few months, basically making them free.
One of the fastest and easiest ways to cut your energy bills is to change a few of your light bulbs to LEDs.
By simply changing one of your incandescent bulbs to LED you will save at least $52 in electricity costs before it burns out.
LEDs not only put money in your pocket because they are more energy efficient but also because they last longer. So you'll keep your lighting costs low for years to come.
Energy savings means that you will be protecting the environment as well. By switching to an LED bulb you'll reduce your carbon footprint by 500 lbs of CO2 emissions.
LEDs also help you think more clearly as their light enhances alertness. They've even been shown to work better at keeping you alert than coffee.
The lighting you choose makes a big difference for the atmosphere and mood of your home. Thankfully LEDs have come a long way when it comes to light quality.
Whether you want soft lights to create a more inviting ambience or you need some bright lighting to get things done, there's an LED for that. All the different types of lighting you've been using for years are now available in a energy saving bulbs.
Where can you use an LED? Nearly every shape of older bulb, from long fluorescent tubes to little flame-shaped candelabra bulbs, is available in an LED version. Many LED bulbs are also dimmable, so you can adjust your lighting to set the right mood.
This all sound good in theory but with all the options out there, finding the perfect bulb can seem daunting. If you’re feeling overwhelmed, don't worry we'll show you how to pick the right LED for each room of your house.
Here's a quick summary of the benefits of switching from a traditional incandescent bulb to LED:
$52 over the lifetime of a bulb i
How long to get back your money
6 months or less
Average CO2 savings
500 lbs over the lifetime of a bulb ii
Better alertness, focus and mood
Proper LED lighting helps you stay focused and has been shown to work better at keeping you alert than coffee iii, iv, v, vi, vii, viii
Lighting your home is no minor expense. It's 15% of the electricity you use. What if you could save a large part of that on your electric bill each month?
You could do this by keeping the lights off most of the time. Not the brightest option though...
Picking the type of bulb that will save you the most is the best way to put money back in your wallet.
When you want to buy a bulb, traditional incandescents are the cheapest but which type of bulb cost the least in the long run?
Although both the CFL and LED have “Energy Savings” labelled on the package, it’s difficult to understand what “Energy Savings” really means in terms of both long-term cost savings. When you actually stop to compare both the cost and energy consumption for just one light bulb, you begin to see what a great investment the LED is, both for your pocketbooks.
|Which 60W equivalent bulbs cost the least in the long run?|
|(all approx. 800 lumens)|
|Bulb Types||Life||Costs*||Year 1||Annual Cost||Total Costs over 7.5 years|
|Standard Incandescent||1 yr||Bulb Cost||$0.50||$0.50||$3.75|
|60 W||Energy Cost||$8.25||$8.25||$61.88|
|Halogen Incandescent||1 yr||Bulb Cost||$1.50||$1.50||$11.25|
|43 W||Energy Cost||$5.91||$5.91||$44.33|
|CFL||3 yrs||Bulb Cost||$2.00||$0.00||$6.00|
|13 W||Energy Cost||$1.79||$1.79||$13.43|
|LED||7.5 yrs||Bulb Cost||$3.00||$0.00||$3.00|
|10 W||Energy Cost||$1.37||$1.37||$10.28|
*Bulb costs are based on average price from major offline and online retailers as of April 2017. Energy costs assume bulb use of 3 hours per day with electricity price of $0.1255/kWhi.
A lot of numbers to go through in this table but as you can see the combined cost of both purchasing and powering an LED is the lowest.
Only CFLs come close, in fact during the first year they are slightly cheaper. But after the second year those saving go to zero.
LEDs save more electricity and last longer so when you replace one of your old incandescent bulbs you will save more than $52.
With LED lighting you can spend a little and get a lot more of what you want. How will you use the savings? A few LEDs will give you a nice pair of shoes and a few more will give you the first payment for that new car you have been looking at.
Switching to LED light bulbs has some obvious perks, they're energy efficient and they last for years. But setting up proper lighting at home gives you a few health benefits as well, like better alertness, focus and mood.iii, iv, v, vi, vii, viii
Light affects your body's biological clock. This 24-hour internal clock is running in the background of your brain and cycles between sleepiness and alertness.
But your internal clock does not react in the same way to all colours of light. Blue light wavelengths have the strongest effect because they give the signal to your body to wakeup and stop producing melatonin, a hormone that helps control your daily sleep-wake cycles.
In the morning, sunlight contains more blue light and life on Earth has evolved to respond this as a signal to wake up.
Blue light is part of the natural mix of light colours that are found in sunlight and are beneficial because they boost attention, energy, and mood. LEDs are also a good source of blue light.
Proper LED lighting helps you stay focused and has been shown to work better at keeping you alert than coffee.
Swedish researchers compared the effects of caffeine and blue light on the brain and found that both boosted alertness. However, people exposed to blue light for an hour performed better on reaction tests than those who had drunk three coffees.iii The alerting response to blue light is effective in reducing sleepiness and enhancing cognitive performance.iv, v, vi
On the other hand, poor lighting can have the opposite effect.
When the lights go down, as when the sun sets, your body will start to produce more melatonin, a hormone that prepares you for sleep. When needed your body will use serotonin, a hormone that influences your mood, and convert it into melatonin. In general, the more melatonin that’s produced, the more levels of serotonin decrease. Researchers have seen that lower serotonin levels leads to lower mood. So a poorly lit room can cause you to feel down.vii, viii
Knowing that, how can you boost the mood in your home?
Consider switching to daylight or cool white LED bulbs (3500 to 5000 Kelvin), as these types of bulbs have more blue light. You can use these in the kitchen for example so that while you are having breakfast in the morning, you'll also feel more energized and ready for the day.
Since bright light can increase alertness, it’s recommended to either dim the lights or use warmer colour temperatures (2700 to 3500 Kelvin) to wind down in the evenings. A good place for warmer bulbs would be in the bedroom to help make falling asleep easier.
Proper lighting will help regulate your internal clock so that day or night you'll be feeling right.
How to pick the perfect energy saving light bulb every time
When a bulb burns out or breaks you don't want to spend hours to find a good replacement. At the same time proper lighting can have a surprisingly big impact on the mood and look of your home. It's amazing how you can change a room or home by just improving the lighting. So when it's time to get a new bulb you want to get it right.
Whether you want to match the colour and brightness of your old bulb or upgrade your lighting there are quite a few options to consider. On top of that, the jargon used on LED packages isn't as illuminating as the technology.
The main things to look for are the shape of the bulb, brightness and colour.
Where can you find this info? Just check on the package. All you have to do is check out the Lighting Facts label located on every bulb.
Let's look at this and make sure that you know how to pick the perfect bulb for any room in your home.
Match the shape by bring your old bulb with you
Have you ever gone to the store and bought the wrong thing? The easiest way to avoid this is to have the right info. LEDs are available in a variety of shapes to fit a range of lamps and lighting fixtures, so there's a lot to choose from. But some LEDs bulbs aren't exactly the same shape as the ones you had before. Because of newer technology, different designs maybe used. The best way to make sure your new LED is a perfect fit is to bring in the old bulbs when you go shopping.
That way you can always compare with the bulbs displayed in the store or just ask for help from employees to make sure you get the size, brightness and colour that's best suited for your home.
Get the brightness just right
How can you make sure that your new bulb will give you the right amount of light? LED bulbs save you energy and money by using less Watts to give you the same amount of brightness. With LEDs the way to measured brightness is not with Watts but with lumens. The more lumens, the brighter the light.
How many lumens do you need? Don't worry you don't have to memorize a whole chart of numbers to buy your next light bulb.
If you look on the box of LED bulbs, you'll see that most of them are "replacements" or "equivalents" for incandescent bulbs of specific wattages.
For example, 800 Lumens is a good all-purpose level of brightness to replace the traditional 60 Watt incandescent light bulb.
Choose the watt-equivalent that best matches the brightness (lumens) you want.
How many lumens do you need?
When replacing a
Look for a bulb that produces
40 Watt bulb
60 Watt bulb
75 Watt bulb
100 Watt bulb
You’ll notice some manufacturers say their 850-lumen bulb is a 75-watt equivalent, but you may be disappointed in the brightness when you get home, so mind the lumens instead.
With lumens listed on the bulb, you'll always have a concrete comparison of how bright any two bulbs actually are.
Create the perfect ambience
If you were turned off by the harsh white quality of light from older LEDs you’ll be glad to know there are more options now. LED bulbs offer a range of colours. From a warmer yellow-white on the low end of the scale, like the colour of incandescent bulbs. To a more pure white in the middle, with a blueish white on the high end.
Light colour temperature is measured on the Kelvin scale. Manufacturers also use descriptive names to better explain what kind of colour light you'll get. Here are the most common ones:
Soft White/Warm White (2700-3000 Kelvin): These bulbs have a warm colour temperature that give of a cozy and diffused light with an amber tint just like incandescent bulbs.
Bright White/Cool White (4000 Kelvin): This colour temperature is closer to pure white and gives rooms a whiter, more energetic feel.
Daylight (5000-6000 Kelvin): Providing the greatest contrast, these cooler lights are more like daylight, with a sharper, brighter light.
You can set the mood of a room by using different colour lighting. So when you are out there picking a bulb you need to keep that in mind to create the right ambience.
A subtle change in colour can make a big difference in the vibe of the room.
Which bulbs have the colour you are looking for? While it maybe hard to figure it out online, the nice thing is that stores have displays where you can see the different types of light before you buy.
If you have to replace a bulb that is beside others or a few bulbs at the same time try and make sure that they have simlar colour temperatures so that things blend in nicely together.
The right lighting can make the colours in your home appear more vibrant, rich and natural. To do this properly, a room with a lot of warm tones like reds, oranges, yellows and skin shades will look best with warm lighting (2700-3500 Kelvin). Cooler shades such as grays, greens, and blues are best complimented by cooler and neutral tones (3500-5000 Kelvin).
Setting the right mood in every room
Many people view lighting as functional and it's importance is often overlooked. The truth is that you don't need expensive furniture or décor to transform a room, all you need to do is upgrade your light bulbs.
As we saw earlier, different types of light can impact how we feel. Warmer colour light is relaxing and cooler shades of light have an energizing effect. So depending on how you use a specific room, you'll make the mood perfect by matching the lighting accordingly.
You want you're lighting to best reflect your needs whether it's a cooler colour to support your concentration while working or a warm light to help you unwind at the end of the day
Every room in your home is different. But in general, warm bulbs can be used for places like the living room, dining room and bedrooms. While cool or daylight bulbs can be used where the details are important like your home office or kitchen.
How to set the mood right in each room? Here's some suggestions on how to get it all done. Of course, there's no strict rules about this so feel free to experiment and see what looks best to you.
Living room (2700-3500 Kelvin)
Your living room is a busy place. During the same day you could be reading a book, hanging out with friends or watching a movie and that's just to name a few. This room is a place for relaxation and entertainment, so you probably don't want any harsh blue lights there.
The best option is to use LED bulbs that are warm and welcoming, like those around the 2700 Kelvin range. Even better would be to use dimmable or 3 way LEDs. They're a perfect fit for the living room because they make it easy get the ambiance just right, whatever you are doing.
Kitchen (3500-5000 Kelvin)
When your recipe calls for finely chopped ingredients or precise measurements you don't want your lighting to let you down. To make sure your recipes come out tasting yummy you need to be able to see clearly in the kitchen. Light that has more blue in it, like bulbs in the 4000 Kelvin range, are great here.
Many of you start your mornings in the kitchen, so this type of lighting will also help you feel more alert and awake while prepping your breakfast.
Bathroom (3500-5000 Kelvin)
Sometimes you miss a spot shaving or mess up your makeup. It happens to everyone but maybe it's not your fault. It could be because of poor lighting.
That's why it's a good idea to have a lot of light in the bathroom. Daylight bulbs are popular here, because they make it easier for you to catch all the little details and make sure you are looking your best.
Dimmable LEDs are super useful in this room because they help make sure you are not blinded by the lights during middle-of-the-night bathroom visits.
Bedroom (2700-3500 Kelvin)
In the bedroom you probably want to go for a relaxed and peaceful feel. Bright lights increase alertness, so you'll want to use lighting that is more on the warm side (2700 to 3500 Kelvin). This will help you to wind down in the evenings and make falling asleep easier.
There's lighting for reading and lighting for romance, in the bedroom you probably need both. By using dimmable or 3 way LEDs you can easily set the lighting to get the mood right.
Home office (3500-5000 Kelvin)
When lighting your home office, you want to make sure that the lights are maximizing your ability to be productive. Putting cool white lights in the office that mimic daylight (5000-6000 Kelvin) will reduce your melatonin levels helping to keep you focused, alert, and energized.
Bright light helps you stay concentrated but you also want to minimizing glare and contrast. This is key to reducing eye strain. Make sure to choose a good place for your light(s) to reduce glare on your computer screen.
Dining room (2700-3500 Kelvin)
Good food and fun times is what the dining room is all about. Like in the living room, soft to neutral tones of lighting are best, like those around the 2700 Kelvin range. They will create an inviting ambiance that is perfect for this part of your home.
Dimmable bulbs are a great add on in this room. Like that you can have good lighting in the morning when you are reading the news or catching up on emails and still be able to set the mood right for a special meal for two in the evening.
Outdoors (2700-3500 Kelvin)
After the sun sets, welcome guests with warm lighting around the house in places like your patio and the front entrance. Don't forget to use outdoor LED bulbs for fixtures that are outside. They are much more durable than bulbs designed for indoor use.
Also keep in mind that unprotected fixtures, like upward facing flood lights for example, can allow moisture to get into the light bulb area. In these types of fixtures it's safer to use bulbs that are rated to work in wet locations.
Dimmers: How to avoid buzzing and flickering
Dimmable LED bulbs let you create the right ambiance for any occasion but if they are flashing on and off or making an annoying hum that will kill the mood.
Being able to adjust your light source means you’re able to create the perfect atmosphere in your home, anytime. From warm and bright to dim and cozy, dimmable LEDs can help create the right lighting.
The first step to make sure everything works well together is to check that the LED bulb's packaging says the word "dimmable" on it. Many LEDs are dimmable but not all so check before you buy, better yet ask someone in store for help.
The thing is that even dimmable bulbs aren't 100% guaranteed to work in every dimmer because of potential current or wiring issues.
So unfortunately, the best way to find out is to try the bulb and if they buzz or flicker, you will know to replace the dimmer.
Newer universal dimmer switches do a better job of controlling the electrical current coming into the bulb and work well with LEDs.
Thankfully dimmer companies test with LED bulb companies and put out compatibility sheets to help you find a combination of the two that works.
Here are the compatibility sheets of major manufactures:
LED bulbs: Cree, Feit, GE, Philips, Sylvania Osram, TCP
Some final tips to find the perfect energy saving bulb
When it comes to light quality, longevity, price and energy efficiency LEDs are the best.
Maybe you are changing the lights because your room feels dark and gloomy. Maybe it's just because the old ones burned out or broke.
Whatever the reason if you choose the right fit, brightness and colour you'll choose the right bulb every time.
Whether you’re setting the mood in the living room or looking for task lighting in the kitchen, LEDs have you covered. With familiar bulb shapes and instant brightness, you are able to create a comfortable environment in every room of your home.
LEDs have come a long way. What use to be kinda clumsy and cumbersome is now super stylish and sophisticated. You've got a lot of style options in LED that you didn't have not so long ago.
Although we won't recommend any specific bulbs in this article one of the best ways to get suggestions would be by going into some stores and checking out their displays or talking with the employees. Another great way is to with friends and family to see what they use or check customer reviews online.
Now that LEDs cost almost the same as CFLs, there is no need to upgrade in phases. You can buy a pack of multiple bulbs to reduce the cost per bulb and then change out old bulbs as they break.
It still makes sense to upgrade a few of the bulbs that get used a lot in your home. If you switch to LEDs in places like your living room or kitchen, you'll save more money, faster.
When you are looking for LEDs to use in 3-way lamps check the packaging as you would do with dimmable bulbs to make sure you're getting the right thing.
Is switching to LEDs worth it?
Switching to LEDs sounds good but it isn’t a one size fits all solution. You might be worried about making a big change to your lighting. If you're have some concerns about making the switch, that's normal. Let's look at the most common ones.
Aren’t LEDs expensive?
No, but they used to be. In 2012 LEDs were extremely expensive, costing $20 or more each. Since then technological advancement have allowed the cost of today’s LEDs to drop significantly. These days for $2-$4 you can find a wide range of LEDs, so it’s much easier to upgrade your lighting.
LEDs no longer have the scary price point they used to and now that they cost almost the same as CFLs, it's a great time to make the switch. LEDs are basically free because they pay for themselves in a few months.
LEDs not only put money in your pocket because they are more energy efficient but also because they last longer. So you'll keep your lighting costs low for years to come.
When most people need to replace their light bulbs, cost is a big factor in their decision. But the actual cost includes more than just the upfront price of each bulb you buy; you should also factor in how much each option will cost to operate over the years.
As with most things, it turns out a bit of money spent today can often lead to substantial savings in the long run.
One of the fastest and easiest ways to cut your energy bills is to change a few of your light bulbs to LEDs.
By simply changing one of your incandescent bulbs to LED can save you at least $52 in electricity costs on average before it burns out.
Where can you use LEDs?
LEDs can be used nearly anywhere that you find other bulbs. Some examples include in recessed fixtures, table lamps, track lighting, ceiling fixtures and porch lights. 3-way and dimmable LEDs are also available for lights needing those bulbs.
Can you count on LEDs to last?
One of the things that sets LEDs apart from other bulbs is how long they can last. Some manufacturers offer LED bulbs with warranties of 10 years or more.
Because LED bulbs aren't made with glass and don't have filaments, they're a lot more durable than other lights.
This isn't to say that LEDs don't fail. They definitely do. As with any device relying on tiny, delicate electrical components things can go wrong.
If that happens before the warranty ends, you can just return it back to the store or manufacturer for a new replacement bulb.
Most major stores like Walmart and Home Depot will accept an exchange, just make sure to have the details handy. To keep track of the start date try marking it on the base of the bulb or on the packaging.
Save all the packaging from the bulb and the receipt, it helps if you tape or staple them together so you don’t lose either. Now when a bulb stops working, you simply return to the store where you got it and say you want to exchange them, it's as simple as that.
Will my home look and feel the same with LEDs?
Lighting can affect how a room looks and feels, and can ultimately affect how you look and feel.
When LEDs first came out most of them had a cooler blue tone. That works for some rooms in your house but there’s just no substitute for the warm, aesthetically pleasing look created by incandescent bulbs.
Now LEDs also come in daylight and warm white colour temperatures. So you can more easily replace any of your existing bulbs without altering the look and feel of your room.
How safe are LEDs?
When accidents happen and a light bulb breaks you'll probably end up with pieces of broken glass everywhere. Even worse, if the bulb is a CFL then the headache of clean up becomes even more complicated because they have mercury in them.
Luckily LEDs are made of plastic so it’s solid structure means shattered light bulbs are a thing of the past. And unlike CFLs, LEDs don’t contain harmful mercury making them a safer option.
On top of that LEDs don't get very hot like other bulbs so kids or family members won’t accidentally burn their fingers on an LED. Because they don't heat up much you also don't have to worry if you leave them on for longer periods of time.
Is there less choice now because of new standards?
New energy efficiency standard for lights have removed some older styles of bulbs from the stores. Your old bulbs may no longer be available but that doesn't mean you are in anyway limited in your options.
The freedom to chose is still yours. All the old bulb options you're used to are now available in the form of energy saving LEDs. From colour to size and brightness, you'll find LED equivalents to your old bulbs plus some new connected options as well.
Energy savings should not come at the expense of the beauty of your home. You want your home to look as beautiful as it did with your old lighting. You can do that with LEDs or maybe even make your home look better.
How can you get rebates?
Many utilities and stores offer energy efficiency rebates, so don't forget to check for them before you buy. Usually instant rebates are clearly marked so you'll find them easily when you go into a store.
Otherwise you can use the Energy Star and Energy Federation sites to figure out which rebates are available based on where you live: Energy Star Product Rebates and Energy Federation Participating Utilities
How to dispose of the CFLs you are replacing?
If the bulb that has broken or burned out is a CFL then special care needs to be taken when you throw it out. You have to use caution when cleaning up a broken CFL. You can find instructions for cleaning up a broken CFL on the EPA’s website. Also, because of the mercury content, you can’t throw CFLs in the trash.
To make sure that your CFLs are disposed safely contact your city for local recycling options. Otherwise take a look at the sites of Earth911 or the EPA for more info. They are also accepted at all Home Depot, IKEA and Lowe’s stores.
The CFL vs LED debate is over, the real question is how will you use the savings?
With low cost LEDs being created in many shapes and sizes, there is no reason to use CFLs anymore. Replacing a broken or burned light bulb is easy once again now that the CFL vs LED debate is over.
LEDs are better than any other type of light bulb because they save you the most money, last years longer than the competition and provide instant high-quality light similar to incandescent light bulbs.
Prices have plummeted, too. Just a couple of years ago, LEDs were going for $20 or more each. These days for $2-$4 you can find a wide range of LEDs, so it’s much easier to upgrade your lighting.
You don’t have to rush out and replace your working light bulbs, but when they burn out, LEDs are the best choice. There is no right or wrong way to make the switch. But the sooner you do, the sooner you’ll start saving.
How much will you save? LEDs pay for themselves in a few months, basically making them free. And they will continue paying you for years.
In fact, one of the fastest and easiest ways to cut your energy bills is to change a few of your light bulbs to LEDs.
Over the longer life of an LED, those savings will be more than $52 when you replace one of your old incandescent bulbs.
How will you use the savings? A few LEDs will give you a nice pair of shoes and a few more will give you the first payment for that new car you have been looking at.
Energy efficiency also means that you will be protecting the environment. There is no question that LEDs are the most environmentally friendly lighting available. They last the longest and use the least amount of energy which reduces your carbon footprint. Switching to an LED bulb will save you 500 lbs of CO2 emissions.
Maybe you are interested in switching to LEDs for the obvious reasons, they save you money and last for years. But setting up proper lighting at home gives you a few health benefits as well, like better alertness, focus and mood. Proper LED lighting will help regulate your internal clock so that day or night you'll be feeling right.
Lighting probably isn’t something you think about on a daily basis, but it’s a big part of our everyday lives.
The lighting you choose makes a big difference for the atmosphere and mood of your home. With soft and warm white hues that mimic the glow of traditional incandescent bulbs, LEDs have also come a long way when it comes to light quality.
If you’re ready to try out LEDs, start by replacing the bulbs in your home you use most often, such as your living room or kitchen lights. Like that you'll be putting money back in your wallet faster.
Switching to LEDs makes you more eco-friendly and econo-smart. Plus you can smile inside knowing that you’re also doing something great for the health of you and your family.
iU.S. Energy Information Administration. Short-Term Energy Outlook - Electricity Section. Washington, DC: 2017.
iiU.S. Environmental Protection Agency. Year 2012 Summary Tables eGRID 10th edition Version 1.0. Washington, DC: 2015.
iiiBeaven C. M. & Ekström J. A comparison of blue light and caffeine effects on cognitive function and alertness in humans. PLoS One 8, e76707, 2013.
ivFigueiro MG, Rea MS. Short-wavelength light enhances cortisol awakening response in sleep-restricted adolescents. Int J Endocrinol. 2012:301935; 2012.
vLori J. Brown, Toine Schoutens, Geoffrey Whitehurst, Troy Booker, et al.. The Effect of Blue Light on Pilot and Flight Attendant Behavioral Alertness. SSRN Transportation. 2014.
viChellappa SL, et al. Non-visual effects of light on melatonin, alertness and cognitive performance: can blue-enriched light keep us alert? PLoS ONE 6, 6:e16429, 2011.
viiStrong RE, Marchant BK, Reimherr FW, Williams E, Soni P, Mestas R. Narrow-band blue-light treatment of seasonal affective disorder in adults and the influence of additional nonseasonal symptoms. Depress Anxiety 26: 273–278, 2009.
viii Anderson JL, Glod CA, Dai J, Cao Y, Lockley SW. Lux vs. wavelength in light treatment of seasonal affective disorder. Acta Physiol Scand 120: 203–212, 2009.
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