How to Buy a Light Bulb

How to buy a light bulb - Who cares? Light bulbs cost under 2 bucks each, right? Wrong. The total cost of a light bulb is the purchase cost plus the cost of electricity it uses. This can be significant and varies greatly by type of bulb. Considering a house may have 50 light bulbs, this can add up to big bucks. In addition, light bulbs have a large influence on the overall mood and safety of a house. Choosing the right type of light bulb for each room deserves some thought and planning.

Shown above (left to right), incandescent, halogen,
fluorescent, and compact fluorescent bulbs.


  • Incandescent - the standard light bulbs that most people are used to. Incandescent bulbs work by using electricity to heat a filament in the bulb until it glows. The filament is either in a vacuum (no air) or in a mixture of argon/nitrogen gas. All incandescent bulbs can be used with dimmers. They product steady warm, white light that is good for most household applications. On the downside, the do produce a good amount of heat which limits their efficiency (LPW of 10 to 20). A standard incandescent bulb can last for 700-1000 hours. Soft white bulbs use a special coating inside the glass bulb to better diffuse the light; the light color is not changed.
  • Halogen - work by passing electricity through a tungsten filament, which is enclosed in a tube containing halogen gas. The light produced is a brilliant white color which is ideal for situations requiring focus on small items such as hobbies, reading, writing, etc. A halogen bulb will last 2,000 to 4,000 hours. However, halogen bulb get much hotter than other bulbs, a 300 watt bulb may get to over 600 degrees F. Attention must be paid to placement of halogen bulb so that they are not accidentally touched and that they don't come in contact with flammable materials (e.g. paper, cloth curtains, etc.) In addition, halogen bulbs come with a glass filter that contains harmful UV within the bulb. Be careful not to touch the glass part of the bulb, the oils from our fingers will shorten the bulb life. Halogen bulbs are less efficient that incandescent bulbs because more of the power is converted into heat.
  • Fluorescent - work by passing a current through a tube (no filament) filled with argon gas and mercury. This produces ultraviolet radiation that bombards the phosphorous coating causing it to emit light. Bulb life is very long 10,000 to 20,000 hours. Fluorescent bulbs are also very efficient, producing very little heat. Historically, there have been problems using fluorescent bulbs outside in cold environment and the light has been of poor quality (i.e. not evenly distributed over the spectrum and fluctuating over time). However, newer bulbs have much better cold weather resistance and use special coatings to provide better quality light. Fluorescent bulbs are ideal for lighting large areas where little detail work will be done (e.g. basements, storage lockers, etc.) Most fluorescent bulb cannot be used with dimmers. Note: fluorescent bulbs need components called ballasts to provide the right amount of voltage. There are primarily two types magnetic and electronic. Electronic ballasts solve some of the flickering and humming problems associated with magnetic ballast and are more efficient, but cost more to purchase.
  • Compact Fluorescent - work like fluorescent bulbs, but in a much smaller package. Only in the last 5 years have become viable alternatives for the homeowner. Newer versions screw directly into the bases for standard incandescent lights. Similar to fluorescent bulbs, they produce little heat and are very efficient. As a rough guide:

  • Compact Fluorescent = Incandescent
    - 4 Watts = 25 Watts
    - 9 Watts = 40 Watts
    - 15 Watts = 60 Watts
    - 20 Watts = 75 Watts
    - 25 Watts = 100 Watts
    - 42 Watts = 150 Watts

    Most cannot be used with standard light dimmers, although more expensive versions are available that do. Typically last for up to 10,000 hours. Compact Fluorescent bulbs are ideal for areas where a moderate amount of detail work is done, e.g. kitchens, dining rooms, living rooms, bedrooms, etc.
  • LED - These are the newest technology. Like flourescent light bulbs they are more efficent than incandescent light bulbs (turn less of the power into heat). LED light bulbs can be dimmed, have a very long life span, and produce a very white light. However, LED bulbs are currently much more expensive than the other types and don't stand up well to extreme temperature change.


  • Efficiency - is measured in light (lumens) per unit of electrical electric power (watt). Typically fluorescent bulbs are the most efficient followed by compact fluorescent, incandescent and halogen.
  • Color - vary across bulb by type and within types. A technical term of color temperature is used to describe the color. Low color temperatures (2700 degrees) are soft and warm. As the color temperature increases the color becomes more of a pure white. Fluorescent bulbs usually describe their color as warm or cool. This doesn't refer to the heat, just the way the color appears: a soft glow versus cool and sterile.
  • Heat - vary across bulbs by type and within type by wattage. Fluorescent and compact fluorescent produce the least amount of heat, followed by incandescent and halogen.
  • Power - typically measured in watts.
    • Operating Costs - To figure out the cost of operating a bulb, multiply the watts times the kilowatt per hour charge from you utility and divide by 1000 (to convert a kilowatt into a watt). For example, a 100 watt bulb * 15 cents / 1000 = 1.5 cents per hour.
    • Circuit Load - To calculate how many bulbs you can safely use on a single circuit, add up the wattage of the bulbs you would like to use and divide by the voltage. For example, 18 bulbs at 60 watts each would consume 18 bulbs *60 watts per bulb /120 volts = 9 amps. Therefore 18 bulbs at 60 watt each could be carried on a 10 amp circuit.
  • Voltage - can be 120 Volts or a light fixture can use a transformer to create higher or lower voltages
  • Connection - screw-in base versus plug-in base

How To Choose

  1. Area Activity - The best light bulb type depends on the activities done in the area:
    • for areas of detailed work (offices, work benches, sewing rooms, etc.) choose a halogen, incandescent or LED light bulb
    • for areas of moderate detailed work (living rooms, kitchens, etc.) choose a incandescent or compact fluorescent light bulb
    • for large areas with little detail work (basements, garages, bathrooms, etc.) choose a incandescent or fluorescent light bulb
    • for areas where heat can be a problem (e.g. a small room with little ventilation) or where the bulb may be brushed against, try to avoid halogen bulbs. If possible try a fluorescent, compact fluorescent or LED light bulb
    • for outdoor areas, consider halogen or incandescent light bulbs
    • for hard to reach fixtures choose light bulbs with a longer life, e.g. long-life incandescent, halogen, compact fluorescent, or LED
  2. Light Color - Try several different types of light bulbs. Choose the color that provides the desired effects
  3. Energy Efficiency - Light bulbs that are used heavily (more than 3 hours a day) and are indoors, consider a fluorescent, compact fluorescent or LED. The higher purchase cost will be easily offset by the electricity savings over the life of the bulb

Written by David Lin.