Living Efficiently With Tom: Efficient Lighting
June 27, 2010 – Changing out inefficient light bulbs is an easy and cost-effective way to cut your energy bills. Replacing a 60 Watt incandescent bulb with a 13 Watt compact fluorescent (CFL) one can save you almost $60 over the life of the CFL – a payback period of about five and a half months.
Look for the ENERGY STAR label when purchasing CFLs. Bulbs that qualify for the label meet certain requirements for performance, quality and low mercury content.
And speaking of mercury, make sure you dispose of broken, burned-out or faulty CFLs properly – don't simply throw them in the trash, as mercury is toxic. Instead, take them to a collection point for CFLs, which can be found at almost any hardware store (however, you would normally get more mercury exposure from eating a can of tuna than you would smashing a CFL bulb).
Number of bulbs
Though you might be inclined to max out the power of bulbs in a given fixture, give some thought to exactly how much light you actually need.
With CFLs and LEDs drawing less energy than incandescents, you can put a lot of lighting into fixtures with limited wattage or amperage. But do you really want to do that? If you put, say, three 100-Watt equivalent CFLs into a fixture that previously had three 30-Watt incandescent bulbs, you won't be saving energy – which is the whole purpose of using CFLs in the first place.
Instead, consider supplementing ceiling lights with standing and table lamps, and turn on only as much light as you need at a given time. If you're sitting on the sofa reading a book, all you need is a single-bulb standing lamp nearby – not a triple-bulb ceiling fixture that lights up the entire room.
When replacing light fixtures, look for the ENERGY STAR label. These will accept plug- or snap-in bulbs, with much of their electronic componentry built into the lamp rather than the bulb (as is the case with screw-cap CFLs). That way, when the bulb burns out it will be cheaper and less wasteful to replace.
Brightness (lumens)
Nearly all screw-cap CFLs are labeled with a number that compares their brightness to the wattage of an incandescent bulb of similar brightness. You can also compare lumens, which are a measure of brightness: 1,100 lumens roughly corresponds to the light of a 75 Watt incandescent bulb. Lumens, like watts, are noted on the product's package; by comparing the two numbers across brands and styles you can see which bulb is more efficient (yes, some CFLs are more efficient than others).
Color Temperature (Kelvin)
The light from CFLs is occasionally described as being 'harsh' or 'blue.' But these days it's easy to find a range of different color temperatures (expressed in Kelvin (K)), from 5000K 'daylight' or 'cool white' to 3000K 'warm white.' If you prefer the warmer, orange-ish tone of incandescent bulbs, look for CFL or LED bulbs closer to 3000K. Remember that shades and fixture covers will also change the light's tone.
Somewhat confusingly, bulbs that produce 'warm white' lighting actually have a lower color temperature than bulbs that produce 'cool white' light. The aesthetic distinction is entirely based on people imagining red to be warm and blue to be cold. In reality, the higher the Kelvin (or, the higher the color temperature), the cooler the color.
In picking out different bulbs for different rooms of our house, I varied the color temperature based on the room. I chose warm-toned bulbs for the bedroom and living room and cool-toned (i.e., whiter) bulbs for the kitchen, office and bathroom as well as for outdoor fixtures.
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| An LED bulb in my front porch light |
Some thoughts on LEDs
Light emitting diodes (LEDs) have been around for a while, but it's only in the past few years that they've been incorporated into general-purpose space lighting. Generally speaking, LEDs are extremely energy-efficient – yet they are also expensive. Thankfully, LEDs are coming down in cost and new, better designs for general lighting are taking to market. We will be seeing a lot more LEDs on the market in the coming years.
LEDs are best suited for directional lighting like flood lights; because of their relatively high cost, they are best used in places where the lights are on much of the time, thus generating savings faster.
Beware, though: an inefficient LED light can use more energy than a good CFL, so look closely at the light output (in lumens) and energy consumption (in Watts) before you buy. Many LED bulbs are also marketed as 'accent lighting'. This means that while they may not emit enough light (lumens) to light up a space, they can be used to interesting aesthetic effect - as in the photo at right.
Resources
- ENERGY STAR light bulbs
- ENERGY STAR light bulb savings calculator [XLS] (this calculator uses slightly different assumptions than those the Alliance uses for its savings calculations)
- LED holiday lights
I am slowly replacing all my CFLs with LEDs. I have found that typically, one watt in an LED will provide 100 lumens. 6 watts, 600 lumens, 8 watts, 800 lumens. Now your getting close to a 60 watt incandescent in brightness with half the energy consumption of a CFL equivalent that will last for 20,000 hours. When I get through refitting my house, I will consume around 300 watts if all my lights were to be on at the same time. And, yes, we still turn out our lights when we leave the room. Payback, who cares?
Depends what you mean by ineffective - if brightness is the issue, that can be identified by the lumens listed on the packaging.
Very roughly, a 60 Watt incandescent bulb could be expected to give off 900 lumens or so. An 100 Watt incandescent would be around 1750 lumens.
So once you have a rough sense of how much light you'll need, you can look for bulbs that give off that many lumens while using the least amount of Watts. Or you can compare bulbs or fixtures by dividing lumens by Watts of each one. The higher the lumens per Watt, the more efficient it is.
LEDs are often (though not always) much more directional than CFLs or incandescent bulbs. Sometimes that's good, sometimes it isn't - it depends what you intend to use it for. Like in the outdoor fixture in the photo in this article - that LED bulb shines downward more than sideways and doesn't give off much upward light at all - but that suits the application well (a front porch light).
I might write an 'aesthetics of efficient lighting' article at some point .
Hi Robert, thanks for your reply.
The Alliance to Save Energy approaches these issues from the point of view of energy efficiency - be it equal utility at reduced energy use or greater utility at equal energy use (as opposed to energy conservation strictly). But a great many people interested in these sorts of topics approach them from an interest in reducing energy bills (the overarching theme behind the 'At Home With Tom' series).
What you describe as a 'flyback effect,' often described by economists as the Jevons effect or the Khazzoom-Brookes postulate (depending on the details of what's being discussed), or more generally as 'rebound,' has been a topic of debate since the 1860s (during the industrial revolution) when it was suggested that increased steam engine efficiency would result in equal or greater coal use. There are situations where this is the case; a very simple example would be someone leaving a CFL light on because it is more efficient than the incandescent bulb they would have previously turned off. Yes, this happens. But if you're interested in reducing your energy use - the premise of this series - that's not such a great idea. Likewise, if you buy a new Energy Star refrigerator to save on your energy bills, are you going to leave the door open because it's more efficient? Unlikely. While Jevons and Khazzoom-Brookes scenarios certainly exist in constrained situations, in the majority of situations a more efficient piece of equipment will be used identically to the equipment it replaced, thus reducing gross and net energy usage. But by all means, this is an important behavioral issue that must be planned for in efficiency program design and implementation (and is an issue for measurement and verification of such programs - often called the 'rebound effect' there). Maybe one of us should do an Alliance factsheet on this issue; it's certainly an interesting topic for consideration - though there's plenty about it on the internet.
As for greenhouse gas policies, the Alliance has long been extensively involved with legislation regarding carbon pricing policies; see, for example, our material regarding the American Clean Energy and Security Act.
I disagree with your assumption that the purpose of high efficiency lighting is solely to save energy. If the consumer derives greater value from more intense lighting at a lower cost he is better off. That additional benefit is worth money to the consumer even if it means that the energy savings are less.
The phonomon of consumers using more energy when it is more efficiently provided , referred to as a "flyback" effect, has been observed since the early days of DSM in the 1980s. Apparently you think this is bad; it is not. Any competent economist will disagree with you on this issue.
I urge you to reorient your thinking on this important issue. The average american citizen is not going to conserve energy if it inconveniences him/her. The price mechanism will save energy in a much more efficient manner. If you really want to save energy then promote the passage of a carbon tax and let it increase electricity prices.
