Green Tech: Energy Efficient Light Bulbs

This is the second article of a series to explore and understand various technologies, products, and practices in the Green Technology movement.

Light bulbs are prolifically visual reminders of how we use electricity in our daily lives. A typical home or office spends as much as half of its electricity consumption in lighting. Yet the basic technology used in a typical light bulb had not changed for more than a century, up until a few years ago. But the past decade has brought many energy-efficient alternatives to incandescent light bulbs, each with benefits and drawbacks.

Besides the obvious energy consumption, or wattage, there are other key aspects that define a light bulb. Among them are the intensity and color of the light, expected life of the bulb, and of course, its price.

Wattage vs. Light Intensity
The intensity or amount of light produced by a light bulb is measured in lumens. For example, a 60W incandescent light bulb produces about 850 lumens. At the same time, a 32W CFL (Compact Fluorescent Lamp) bulb is capable of producing more than 2,400 lumens, or more than five times as much light for the same wattage. So to compare the light intensity of bulbs you need to compare their lumens, and not their wattage. This is because the more efficient light bulbs convert more of the electrical energy into light, rather than wasting it into heat. If we were to rank bulb types by their energy efficiency, starting with the least efficient, the list would look like this: Incandescent, Halogen, CFL/Fluorescent, LED (Light Emitting Diode.)

Color Temperature
The light coming from a light bulb has a particular color or color temperature, which highly depends on the type of bulb. For example, the color temperature of the light from a basic CFL looks white or cold compared to that of an incandescent bulb. Color temperature is measured in kelvins (K), with the typical “Soft White” incandescent emitting around 3,000K. The higher the number, the more white the color. So to get a bulb with similar color temperature as an incandescent, pick one with 3,000K or less; otherwise you may end up with a bulb that emits relatively white or bluish light.

Lifespan
A typical incandescent bulb is supposed to last for about 1,000 hours of operation. That number is in the range of 2,000 for Halogen, 6,000-15,000 for CFL, and more than 30,000 for LEDs. So there is a relatively direct relationship between power consumption and lifespan of a light bulb.

Cost
While the energy efficient light bulbs save energy costs over their operating life compare to an incandescent, none can still match the price of one. A typical incandescent goes for less than a dollar, while an equivalent Halogen is around $5-$7, CFL $5-$8, and an LED in the $30-$50 range. Based on these prices, a CFL would make the most financial sense, especially since Incandescents will soon be banned for sale in the U.S anyway.
CFLs, however, come with a few drawbacks compared to Incandescents. First, you have to pick the one with the right color temperature. This can be a daunting task since you also need to decide between the right light intensity and bulb shape in addition to the three color temperature choices. Second, CFLs don’t get to full brightness for up to one minute after they’re turned on, which could require some patience until you get used to them. Third, most CFLs are not dimmable, unless you buy a more expensive model that allows dimming. So if you use dimmers in your house, take that into account. And last, because they use mercury vapors to generate light, they require careful disposal to prevent toxic exposure.
With all that said, CFLs offer the best compromise between cost and energy –efficiency today. That is, of course, until the cost of LED bulbs come down to the sub-$10 range.