Why Use CFLs?

Lighting accounts for close to 20 percent of the average home’s electric bill. ENERGY STAR-qualified CFLs use up to 75 percent less electricity than incandescent light bulbs, last up to 10 times longer, cost little up front, and provide a quick return on investment.

For more information about compact fluorescent bulbs, visit http://www.energystar.gov/cfls

  • If every American home replaced just one light bulb with an ENERGY STAR qualified bulb, we could save enough energy to light more than 3 million homes for a year, more than $600 million in energy costs, and prevent greenhouse gases equivalent to the emissions of more than 800,000 cars.

  • In 2007, Americans saved $1.5 billion by switching to ENERGY STAR qualified CFLs. The energy saved could light all the households in a city the size of Washington, D.C., for over 30 years. Put another way, changing these bulbs removes as much greenhouse gas pollution as planting 2.85 million acres of trees or taking 2 million cars off the road each year.

  • Using ENERGY STAR qualified CFLs results in less mercury in our environment. Coal-fired power plants are the largest source of human-caused mercury emissions in the United States. A coal-fired power plant produces 13.6 mg of mercury to power one 60 watt incandescent bulb, but only 3.3 mg to power an equivalent CFL. Even with 5 mg of mercury inside, using CFLs results in 5.3 fewer milligrams of mercury compared to incandescent bulbs.

  • The average ENERGY STAR qualified light bulb is designed to last 8,000 hours – more than 7 years based on typical household use. That's long enough to earn an undergraduate and graduate degree at ASU.

Yes, CFLs contain mercury

CFLs contain a very small amount of mercury sealed within the glass tubing – an average of 4 milligrams. By comparison, older thermometers contain about 500 milligrams of mercury – an amount equal to the mercury in 125 CFLs. Mercury is an essential part of CFLs; it allows the bulb to be an efficient light source. No mercury is released when the bulbs are intact (not broken) or in use.

Most makers of light bulbs have reduced mercury in their fluorescent lighting products. Thanks to technology advances and a commitment from members of the National Electrical Manufacturers Association, the average mercury content in CFLs has dropped at least 20 percent in the past year. Some manufacturers have even made further reductions, dropping mercury

More about mercury emissions

EPA estimates the U.S. is responsible for the release of 104 metric tons of mercury emissions each year. Coal-fired power generation accounts for roughly 40 percent of those mercury emissions. Mercury released into the air is the main way that mercury gets into water and bio-accumulates in fish. (Eating fish contaminated with mercury is the main way for humans to be exposed.)

Most mercury vapor inside fluorescent light bulbs becomes bound to the inside of the light bulb as it is used. EPA estimates that the rest of the mercury within a CFL – about 14 percent or 0.6 mg – is released into air or water when it is sent to a landfill, assuming the light bulb is broken. Therefore, if all 290 million CFLs sold in 2007 were sent to a landfill (versus recycled, as a worst case) – they would add 0.16 metric tons, or 0.16 percent, to U.S. mercury emissions caused by humans.

For more information on all sources of mercury, visit http://www.epa.gov/mercury

Mercury math

Electricity use is the main source of mercury emissions in the U.S. CFLs use less electricity than incandescent lights, meaning CFLs reduce the amount of mercury into the environment. As shown in the table below, a 13-watt, 8,000-rated-hour-life CFL (60-watt equivalent; a common light bulb type) will save 376 kWh over its lifetime, thus avoiding 4.6 mg of mercury. If the bulb goes to a landfill, overall emissions savings would drop a little, to 4.0 mg. EPA recommends that CFLs are recycled where possible, to maximize mercury savings.



Light Bulb Type

Watts

Hours of Use

kWh Use

National Average Mercury Emissions (mg/kWh)

Mercury from Electricity Use (mg)

Mercury from Landfilling (mg)

Total Mercury (mg)

CFL

13

8,000

104

0.012

1.2

0.6

1.8

Incandescent

60

8,000

480

0.012

5.8

0.0

5.8


Because CFLs also help to reduce greenhouse gasses, other pollutants associated with electricity production, and landfill waste (because the bulbs last longer), they are clearly the environmental winner when compared to traditional incandescent light bulbs.

Handle CFLs with care

CFLs are made of glass and can break if dropped or roughly handled. Be careful when removing the bulb from its packaging, installing it, or replacing it. Always screw and unscrew the light bulb by its base (not the glass), and never forcefully twist the CFL into a light socket. If a CFL breaks in your home, follow the EPA's recommendations. If a CFL breaks in your ASU residence hall, call your front desk for immediate cleanup. Used CFLs should be disposed of properly (recycled) according to EPA recommendations, or by placing a Residence Hall service request.

Can a broken CFL cause mercury poisoning?

Mercury is toxic in high doses. CFLs contain an average of 4 mg of mercury – an amount that would fit on the head of a pin. While that amount is not likely to present excessive risk, any mercury spill should be handled carefully (see EPA recommendations).

Every situation is unique. That said, we like the way this article by Harvard professor Helen Suh MacIntosh breaks it down:

    "A CFL containing 5 mg of mercury breaks in a bedroom that has a volume of about 25 m3 (which corresponds to a medium sized bedroom). The entire 5 mg of mercury vaporizes immediately (an unlikely occurrence), resulting in an airborne mercury concentration in this room of 0.2 mg/m3. This concentration will decrease with time, as air in the room leaves and is replaced by air from outside or from a different room. As a result, concentrations of mercury in the room will likely approach zero after about an hour or so."

    "Under these relatively conservative assumptions, this level and duration of mercury exposure is not likely to be dangerous, as it is lower than the US Occupational Safety and Health Administration (OSHA) standard of 0.05 mg/m3 of metallic mercury vapor averaged over eight hours. [To equate these values, we could estimate the average indoor airborne mercury concentration for 8 hours, beginning post-spill at an estimated starting value of 0.2 mg/m3 and decreasing from there. If one assumes that the air exchanges completely in one hour (a fairly standard assumption), then the 8-hour average concentration would be 0.025 mg/m3.]"

Sources:

http://www.energystar.gov/cfls

http://www.energystar.gov/ia/partners/promotions/change_light/downloads/Fact_Sheet_Mercury.pdf