What is the efficiency of a fluorescent lamp?

Answer 1

It depends on how you define efficiency. Efficiency is a measure of how one item performs in comparison to another. One single item does not have any efficiency by itself.

If by efficient you mean what it costs to operate, the higher the wattage the less efficient it is. But with higher wattage you also get more light.

If by efficient you intend to compare incandescent bulbs of the same wattage with one another, you want to compare lumens, which is the measure of actual light output. Comparing 2 bulbs of the same wattage, the bulb with the higher lumens would be considered more efficient than the other.

Compact fluorescent bulbs (CFL) are considered more efficient than incandescent bulbs because they put out much more lumens for the same wattage. A 13W incandescent puts out almost no light at all. A 13W CFL puts out what is about equivalent in lumens to a 60W incandescent. Since watts are the measure of power used, a 13W bulb is more efficient than a 60W bulb with similar lumens.

In electrical physics, heat is a measure of inefficiency. The most efficient electrical equipment would do its work while producing almost no heat at all. This means that as a matter of physics, an incandescent bulb is terribly inefficient because it puts out a lot of heat.

Answer 2

In general, the incandescent lamp is less efficient than the fluorescent lamp. Fluorescent lighting fixtures are more expensive initially, but they pay for themselves in a relatively short time because they can easily generate the same amount of light using considerably less energy. It's that simple. Incandescent lamps heat a metal filament to white hot to get that metal to incandesce and emit light. But the thermal energy that the filament generates that is not optical light is "wasted" by the device. Fluorescent lamps ionize gases and generate light by fluorescence, and this creates less heat than an equally luminescent incandescent lamp. Much less, in fact. Links are provided below for more information.

It works on the prinicpal of electrical resistance. The electric current flows through the filament of the bulb, suspended in the inert (no oxygen, which hastens burning) interior of the bulb. The filament is a very thin wire of a very tough element known as tungsten. The tungsten filament resists flow of the electrical current to the extent that it glows white hot. This produces heat (about 60%) and light (about 40%). That is how incandescent bulbs work.

Another Answer

You should be asking, "What is the EFFICACY of an incandescent lamp and a fluorescent lamp?"

'Efficacy' is not the same thing as 'efficiency'. Efficacy compares the output power (luminous flux), of visible light expressed in lumens, with the inputpower, expressed in watts. Efficacy, therefore, is expressed in lumens per watt. 'Efficiency' on the other hand, compares total (heat plus visible light) output power, expressed in watts, with input power expressed in watts -which means efficiency has no units of measurement.

Typical efficacies for GLS incandescent lamps range from 5-15 lumens per watt. Typical efficacies for fluoresencents range from 50-100 lumens per watt.