Frequently Asked Questions

General Information

ENERGY STAR is a government program sponsored by the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE). ENERGY STAR helps consumers identify energy efficient products. Look for the ENERGY STAR designation when purchasing bulbs, appliances, home electronics and heating and cooling equipment.

ENERGY STAR certified bulbs save money, energy and time. They use nearly 75 percent less energy than incandescent bulbs and last up to 10 times longer while providing the same amount of light.

LEDs are small light sources that become illuminated by the movement of electrons through a semiconductor material. Many LED products are now found on store shelves. For the highest quality, buy bulbs with the ENERGY STAR logo.

CFLs come in many shapes and sizes to fit in common household light fixtures. CFLs are different from tube fluorescents. For the highest quality, buy bulbs with the ENERGY STAR logo.

Halogen bulbs are a type of incandescent lamp that uses a combination of halogen and tungsten filaments. They are up to 25 percent more efficient than traditional incandescent bulbs.


Buying ENERGY STAR Bulbs

ENERGY STAR bulbs can replace standard incandescent bulbs in almost any fixture. Specialty bulbs include globe lamps for your bathroom vanity and chandelier bulbs or lamps for recessed downlights. Check the packaging of the bulb to ensure it’s meant for your intended purpose.

Certain bulbs are appropriate for outdoor use. Bulb packaging provides information on temperature ratings and outdoor uses.

All ENERGY STAR certified bulbs come with a warranty. Refer to the bulb packaging for details. Warranties range from two to three years for residential use. Keep your receipt in case your bulb does not last as long as advertised.

While you will save energy by using an ENERGY STAR light bulb over an incandescent, read the packaging carefully to determine how the advertised savings were calculated. Rates, timeframes and number of bulbs used to calculate the savings can vary. Most manufacturers use an electric rate based on a national average. Keep in mind that Idaho Power’s residential rate is generally lower than the national average. Calculations on a multi-pack may group the savings into one larger number that adds the savings from all the bulbs. Additionally, savings may be reported as yearly savings or over the life of the bulb.

A watt measures how much energy a bulb uses. Although we associate higher wattage bulbs with greater light output, watts are not technically a measure of brightness. However, for replacing incandescent bulbs, watt equivalents can help narrow the search for the right bulb. The packaging for most ENERGY STAR bulbs provides the wattage of the bulb and the incandescent equivalent.

A lumen is the measurement of light output. The higher the lumens, the brighter the bulb. Two bulbs that use 15 watts can range in brightness. A 13-watt bulb with a brightness of 800 lumens puts out more light for the same energy as a 13-watt bulb with a brightness of 750 lumens.

There are many shades of white light measured in degrees of Kelvin (K). Warm colors work well in area lighting or mood lighting and have lower Kelvin temperatures. Use cooler lights with a higher Kelvin temperature, such as “daylight” or “bright white” for a bluer color. Cool colors work well for tasks like reading.

side by side light color comparisons with a teddy bear and a lamp. warm white and soft white scale from 2700 kelvin to 3000 kelvin. cool white, neutral and bright white scale from 3500 kelvin to 4100 kelvin. natural or daylight scale from 5000 kelvin to 6500 kelvin.



Yes. Only certain bulbs are made to work on dimmers. The packaging information identifies whether the bulb is for use in a dimmable fixture. Dimming a bulb not designed to work with a dimmer switch may shorten its life or impact its performance.

CFLs contain a small amount of mercury sealed within the glass tubing, an average of 5 milligrams. By comparison, the average home thermometer contains 500 milligrams of mercury.

Fluorescent light bulbs, including CFLs, contain a small amount of mercury. Idaho Power encourages safe handling and proper disposal of fluorescent bulbs. Please contact your local landfill or solid waste collection company for information on household hazardous waste collection programs or special handling requirements. Learn more at

While it is hard to know exactly why a bulb may fail, some items to consider include:

  • Was it an ENERGY STAR bulb? Bulbs must meet stricter quality control guidelines to receive the ENERGY STAR designation. If the bulb was an ENERGY STAR bulb, report the failure through
  • Was it the right bulb for the application? Bulbs used with dimmer switches, three-way switches, motion sensors or outdoors must be rated for that use.
  • Was the bulb placed in an enclosed fixture? Before using a bulb in an enclosed fixture, consult the product packaging. Bulbs not designed for totally enclosed fixtures will typically carry a disclaimer indicating they are not intended for this type of application. Because enclosed fixtures do not allow air to circulate around the lamp, heat builds up, which can lead to performance issues.

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