Lighting Frequently Asked Questions

Light Bulb Basics

Q: What are lumens?
A: Lumens are a measurement of how much visible light a bulb produces rather than how much energy it uses (which is measured in watts). A bulb with more lumens produces brighter light, less lumens means dimmer light.

Q: What are watts?
A: Named after the Scottish engineer James Watt, watts measure the amount of energy consumed by a light bulb (or any device). Traditionally, with incandescent bulbs, it was the way to determine a bulb’s brightness.

Q: Can CFLs/LEDs be used in recessed cans, outdoor lights, or track lighting?
A: Yes.

Q: Do CFL/LEDs create heat?
A: Yes, but much less than incandescents. Most CFLs are more sensitive to heat than ordinary bulbs, so they generally need more air space to dissipate heat. Unless your CFL is specifically rated for use in airtight enclosed fixtures and recessed cans, the heat build-up will harm the electronic ballast and can dramatically shorten its life.

Q: Are CFL/LED bulbs dimmable?
A: Both CFL and LED bulbs are available in dimmable models. Check the packaging and your fixtures to make sure you only use dimmable bulbs with dimmer switches.

Q: Do CFL/LED come in 3-way?
A: Yes. Be sure to only use 3-way bulbs in 3-way fixtures.

Q: Can CFLs/LEDs be put on a timer?
A: Yes. Timing controls work well with CFLs and LEDs, as they do not interrupt the circuitry. This is also true with manual timers that use pins for setting on and off times.

Q: Do newer energy-saving bulbs always fit in existing light fittings?
A: Generally speaking, yes. CFLs and LEDs are manufactured using the same screw-in bases as incandescent bulbs. However, if you wish to dim them you will need to purchase a dimmer switch that is specifically rated for CFL or LED. Using a regular dimmer switch will damage the electronics in LEDs and cause CFLs to burn out faster.

Q: Is it true that CFLs/LEDs don’t always work in cold temperatures?
A: Some CFLs take a little longer to reach full brightness in cold temperatures. Others are designed to be "instant on" and have no noticeable warm-up period. Extreme cold temperatures can reduce the lifespan of some LEDs.

Q: Do CFLs/LEDs come in a variety of styles, shapes, and sizes?
A: Yes.

Q: Are CFLs/LEDs available in specialty bulbs?
A: Yes. Every year, they’re becoming available in more and more specialty applications. Ask your retailer or shop online for the specialty you want.



Q: Why are incandescent light bulbs going away?
A: Because they are very inefficient, waste energy, and contribute to carbon in the atmosphere. With more efficient bulb technologies readily available, there’s no need to keep using incandescents.


Compact Fluorescent Lamps (CFLs)

Q: How do CFLs work?
A: Like a regular fluorescent lamp, a CFL is a very low-pressure, mercury-vapor, gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. CFLs use a tube that is curved or folded to fit into the space of an incandescent bulb.

Q: How long do CFLs last?
A: On average, they last eight to 15 times longer than incandescent lamps, or from 6,000 to 15,000 hours.

Q: Does switching CFLs on and off shorten their life?
A: Yes, that can happen. Switching them on and off frequently is not recommended. For instance, when leaving a room, leave the light on if you expect to be back within 15 minutes.

Q: Do CFLs take longer to reach their full brightness?
A: Generally they take up to a minute to reach their full brightness. Many switch on faster and some reach full brightness immediately.

Q: Do CFLs get hot?
A: Yes, they can get hot to the touch. They should be used in fixtures with good airflow, such as a table lamp. If you wish to use them in a recessed fixture, choose CFLs specifically designed for that purpose.

Q: Is it true that because of high energy use at start-up, CFLs have to remain switched on for 45 minutes before they bring any energy saving at all?
A: No. The energy use of CFLs in the first two to three seconds of their operation is slightly higher, but after that their power uptake is stabilized. In practice, they provide energy savings right from the moment they’re switched on.

Q: Do CFLs buzz and flicker?
A: Like tube fluorescent lights, CFLS can flicker and buzz when first turned on. This is due typically to a delay in getting sufficient electric charge to the bulb, often caused by a faulty ballast. Ballasts control the amount of electricity that is drawn in by the bulb and provide a starting voltage for it. Ballasts that do not supply steady, uninterrupted power to the bulb can cause it to flicker. Flickering did happen with earlier CFLs with magnetic ballasts. New ones use electronic ballasts, which are faster.


Light Emitting Diodes (LEDs)

Q: How do LEDs work?
A: An LED (light-emitting diode) is a semiconductor light source. When an LED is switched on, electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence. LEDs present many advantages over incandescent light sources, including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching.

Q: Why do LEDs cost more?
A: LEDs powerful enough for room lighting require more precise current and heat management than incandescent and CFL sources of comparable output. This costs more money to produce.

Q: How much energy do LEDs bulbs save?
A: ENERGY STAR qualified LEDs use only 20–25 percent of the energy of incandescent lights. So your energy consumption for lighting will drop by 75-80 percent.

Q: How much money will LEDs save me on energy bills?
A: If you replace a traditional 60-watt incandescent bulb with an 8-watt LED and the light is on eight hours a day for one year (2,920 hours), your electrical consumption will be reduced by 152 kw-hours per year. Based on electricity cost of $0.18/kWh, you would save about $27 per year for each LED bulb. A house that switched 20 light bulbs (with similar usage) could save more than $500 per year.

Q: Do LEDs last longer?
A: Yes. They last up to 35 times longer than incandescent bulbs.

Q: Do LEDs get hot?
A: They can get hot, especially if there isn’t an adequate heat sink to dissipate the heat. LED performance depends on the ambient temperature of the operating environment. Overheating the LED package may eventually lead to device failure. This concern applies mostly to specialty applications (e.g., automotive, medical, military) rather than residential use.

Q: Are LEDs toxic or dangerous?
A: LEDs are not considered toxic. LEDs have the advantage over CFLs in that they do not contain mercury, but they may contain small amounts of other hazardous metals such as lead or arsenic. Most LEDs are considered safe to use under all conditions of normal use. However, light from an LED is more direct, so you should not look directly into the light, especially with higher power lamps.


Halogen Lamps

Q: Aren’t Halogen lamps also a good option for saving energy?
A: Halogen lamps are more efficient than traditional incandescent bulbs, but they are nevertheless an incandescent light source and much less efficient than CFLs and LEDs.



A: ENERGY STAR is an international standard for energy-efficient consumer products originated in the United States. It was created in 1992 by the Environmental Protection Agency and the Department of Energy. Devices carrying the Energy Star mark generally use 20–30 percent less energy than required by federal standards.

Q: Are ENERGY STAR certified bulbs more expensive?
A: Given that they meet rigorous efficiency and performance standards, ENERGY STAR certified lights may cost a bit more, but their greater longevity and energy savings yield an overall higher value.

Q: What if I buy light bulbs that aren’t ENERGY STAR certified?
A: You may be buying lights that are not as energy-efficient, don’t last as long, and don’t perform as well.

Q: Will ENERGY STAR qualified CFLs/LEDs fit into my existing fixtures?
A: Yes.

Q: How much energy will I save by using ENERGY STAR qualified CFLs/LEDs?
A: ENERGY STAR certified light bulbs use about 75 percent less energy than a traditional incandescent bulb. They also produce about 75 percent less heat, so they are safer to operate and can cut energy costs associated with home cooling. To put it into a larger perspective, if every American home replaced just one light bulb with a light bulb that's ENERGY STAR certified, we would save enough energy to light three million homes for a year, save about $600 million in annual energy costs, and prevent nine billion pounds of greenhouse gas emissions per year, equivalent to those from about 800,000 cars.

Q: How much money will I save?
A: It will depend on the particular bulb model, but on average, each ENERGY STAR certified bulb will save about $6 a year in electricity costs and more than $40 over its lifetime.


Energy Savings

Q: Why is it so important to save energy on lighting?
A: On average, residential lighting contributes to 12 percent of a household’s total electric consumption. So it’s an easy way to save energy and money and reduce carbon emissions without any sacrifice in performance, quality, or convenience.

Q: Should I always turn off lights when not using them?
A: Yes, in most instances. With CFLs, you can leave them on if you intend to need the light again within 15 minutes.

Q: Is it mandatory that I use CFL or LED lights?
A: No. Although some countries are contemplating banning incandescents altogether.

Q: I want to switch my incandescent light bulbs to CFLs/LEDs. What should I do with my current bulbs?
A: Recycle them if possible. Otherwise dispose with your regular trash. You can save your incandescent bulbs that aren’t burnt-out for your fixtures where CFLs aren't suitable, like in a closet where the light would only be on for a few minutes at a time or for a dimmable fixture if you don't have a dimmable CFL.

Q: Is it true that more materials and energy are needed to produce and ultimately dispose of a CFL than an incandescent bulb? Doesn’t this outweigh the benefits of its energy efficiency?
A: No. The energy savings from the use of CFLs outweigh the environmental impact of their production and end-of-life. Using CFLs reduces the overall energy use and the environmental impact of lighting.* Furthermore, by using one CFL, you negate the need to manufacture and dispose of five incandescents.

* Source: Link opens in new window - close new window to return to this page.


Light Color

Q: What do “cool” and “warm” mean on the Lighting Facts label?
A: These are terms that describe the relative color quality emitted by the lamp. Cool light has a more of a blue cast; warm light is more yellow.

Q: Do LEDs or CFLs give off different colors?
A: They can. CFLs typically give off a more cool or blue light, although this is changing. You should always check the package to be sure. LEDs can emit a variety of colors, depending on the particular model and application. Again, always check the package.

Q: What does K stand for?
A: K stands for Kelvin, the standard unit of measurement for light color. Higher Kelvin numbers are more blue, and lower Kelvin numbers are more yellow, like candlelight.

Q: Do CFLs or LEDs produce full spectrum or natural light?
A: While “full-spectrum” and “natural light” are not precise or technical terms, they are generally accepted to mean light that approximates sunlight’s visible spectrum. The light from most LEDs and CFLs do not fit this description, even if it appears “white.” If you require full-spectrum light, you should buy specialty lamps designed for your particular application.


Recycling & Disposal

Q: How should I dispose of CFLs and LEDs?
A: NYSERDA and the EPA encourage New York State residents to recycle CFLs safely to prevent the release of mercury into the environment and allow for the reuse of glass, metals, and other materials. Many municipalities accept them at household hazardous waste facilities and many retailers will recycle CFL bulbs purchased through them.

LEDs can be disposed of in the same way as incandescent bulbs—include them with your regular trash. However, most LED lights today are made with materials that are all recyclable.

Q: What should I do when a CFL breaks?
A: A broken CFL containing a small amount of mercury is unlikely to present any excess risk to you or your family. However, proper cleanup methods should be followed:

  1. Before cleaning up, ventilate the room. Make sure that people and pets leave the room, and don't let anyone walk through the breakage area for 15 minutes. Be sure to open a window and shut off the central forced-air heating/air conditioning system, if you have one.
  2. On hard surfaces, use stiff paper or cardboard to carefully scoop up glass fragments and powder and place them in a glass jar with a metal lid or in a sealed plastic bag. Use sticky tape to pick up any remaining small glass fragments and powder. Wipe the area clean with damp paper towels or disposable wet wipes and place them in the glass jar or plastic bag. DO NOT use a vacuum or broom to clean up the broken bulb on hard surfaces. This will only spread the particles in the room.
  3. If vacuuming is needed after all visible materials are removed, vacuum only the area where the bulb was broken. Remove the vacuum bag, or empty and wipe the canister, and put the bag or vacuum debris in a sealed plastic bag.
  4. Immediately place all cleanup materials outside the building in a trash container or outdoor protected area for the next normal trash disposal day. Wash your hands after disposing of the jars or plastic bags containing the materials.


Lighting Facts Label

Q: The FTC has mandated a new Lighting Facts label. On which lighting products is the new label required?
A: The label applies to packaging for most general-service “lamps” with medium screw bases.

Q: When did the new labeling requirements take effect?
A: January 1, 2012.

Q: What prompted this change to the labeling requirements?
A: The label was designed primarily to simplify lighting purchases for consumers. The Lighting Facts label provides information essential to evaluating products and identifying the best options.

Q: What information must appear on the Lighting Facts label?

  • The light output of each lamp included in the package, expressed as “Brightness” in average initial lumens.
  • The estimated annual energy cost of each lamp included in the package based on the average initial wattage, a usage rate of three hours per day, and 11 cents ($0.11) per kWh.
  • The life of each lamp included in the package, expressed in years rounded to the nearest tenth (based on three hours of operation per day).
  • The color temperature of each lamp included in the package, as measured in degrees Kelvin, expressed as “Light Appearance,” and conveyed by a number and a marker placed proportionately on a scale ranging from 2,600 K on the left to 6,600 K on the right.
  • The wattage for each lamp included in the package, expressed as “Energy Used” in average initial wattage
  • The ENERGY STAR logo for qualified products.
  • The design voltage of each lamp included in the package, if other than 120 volts.
  • For any general-service lamp containing mercury, the following statement: “Contains Mercury/For more on clean up and safe disposal, visit opens in new window - close new window to return to this page..”

Q: What information must appear on the light bulb itself?

  • The lamp's average initial lumens (expressed as a number rounded to the nearest five).
  • For general-service lamps containing mercury, the following statement: “Mercury disposal: opens in new window - close new window to return to this page..”


Mercury (CFLs Only)

Q: Why use CFLs if they contain mercury?
A: Mercury is an essential part of a CFL, allowing the bulb to be an efficient light source. Like all fluorescent lighting, CFLs contain small amounts of mercury—on average, four to five milligrams, about enough to cover the tip of a ballpoint pen. Using energy-efficient CFLs reduces demand for electricity, which in turn reduces the amount of coal burned by power plants and the amount of mercury emitted when coal is burned.

Q: Does mercury escape into the atmosphere when using a CFL?
A: No. Mercury is not released when CFLs remain intact (not broken) or while they are in use. The only time mercury from a CFL is emitted into the environment is when a CFL breaks. When CFLs are recycled properly the mercury remains safe and can be repurposed.

Q: What do I do if a CFL bulb breaks?
A: Review the cleanup proceduresLink opens in new window - close new window to return to this page..

Q: Is there a difference in mercury content between ENERGY STAR and non-ENERGY STAR CFLs?
A: All ENERGY STAR qualified CFLs have less than five milligrams of mercury (some manufacturers are able to produce CFLs that have only one milligram of mercury). Avoid purchasing non-ENERGY STAR CFLs, as they can have up to 15 milligrams of mercury in them—three times as much as the maximum amount allowed in an ENERGY STAR certified CFL.

Q: Can I tell how much mercury is in a CFL before I purchase one?
A: All ENERGY STAR qualified CFLs are required to list their mercury content on the packaging (as of September 2008). Avoid purchasing non-ENERGY STAR CFLs because this information is not required on their packaging.