When buying light bulbs for their home, the first thing folks will look at is the wattage thinking that the higher the number, the brighter the light. However, the reality is that wattage is a measure of power consumption and not brightness.
Although, the relationship between the two holds true for incandescent and halogen bulbs, when it comes to the more popular fluorescents or LED’s of today, the situation can become confusing.
A watt is a measure of power and is calculated by multiplying the voltage in volts by the current in amps. However, because of the fact that higher power consumption by an incandescent bulb causes the filament to become hotter, it glows brighter thereby producing more light.
Lumens vs. Watts
To get a more useful comparison between incandescent bulbs and Compact Fluorescent Lights or LED’s, consider instead the amount of lumens the bulb is rated for. A lumen is the amount of light intensity falling on one square foot of area measured one foot away. However, no need to worry about getting out a light meter and ruler since the manufacturer has already done the calculations for you.
For example, a hundred watt incandescent bulb will produce about 1,600-1,750 lumens. They vary for many reasons, such as the type of coating on the inside of the bulb, the alloy used for the filament and other factors. By comparison, a compact fluorescent light or CFL might consume only twenty watts yet produce about the same amount of illumination.
Similarly, an LED bulb, which is actually composed of many light-emitting diodes within one enclosure, which produces an equivalent quantity of light, might well consume only a few watts of electrical power.
From these numbers it is easy to see why CFL’s and LED’s are becoming more popular, even though their initial cost is a lot higher. Nevertheless, they consume so much less power that, as the bulb prices go down and the cost of electricity rises, they become more attractive. Over ten years, at ten cents per kWh, the savings are approximately $350 for a single LED over the power many incandescent bulbs would need.
Compare Light Bulb Color Temperature
However, the comparisons do not stop with the amount of electricity consumed and the cost. There are differences among the three in something called color temperature that can form a big part of the choice to go with one or the other.
Human eyes evolved to see in natural daylight and, to a certain degree, moonlight that is reflected sunlight. The surface temperature of the sun is about 6,000K. (K stands for Kelvin; K = 273 + C, where C is Celsius). Because of the relationship between the temperature of the sun’s gases and light wavelengths along with the effects of the Earth’s atmosphere, the sun produces light that is perceived as more or less white. That relationship between temperature and color gave rise to the term ‘color temperature’.
The light from incandescent bulbs ranges from a yellowish to a bluish-white, but all do a good job of approximating what our eyes see as ‘natural’, even at the much lower color temperature of approximately 2,700K. Traditional fluorescents, because they contain mercury vapor, give off a more greenish cast while newer compact fluorescent lights manage to produce a hue much closer to natural white light while LED’s are even closer.
Therefore, when comparing bulbs, look on the packaging for the color temperature figures. That hue plays a part in the ease of reading and other tasks that home lighting is designed for. It will affect eye fatigue, and therefore the chance of headaches. It influences the general efficiency with which you can perform those tasks.
Light Bulb Life Expectancy
A normal incandescent will last from seven hundred to a thousand hours. At the higher number, used four hours per day it will last about two-thirds of a year. A good compact fluorescent light or CFL may last up to fifteen thousand hours, which equates to about ten years if used for the same amount of time. An average LED bulb is rated at 50,000-60,000 hours. With an average use of four hours per day, that is over forty years of use. The higher initial cost is not so expensive after all.
Which is best depends on your budget, your cost of electricity and how often you want or need to buy bulbs. However, as the price of CFL’s and LED’s continues to fall, they look to be a far better investment especially for those long-term applications.