How Much Power Do CFL Bulbs Consume?

CFL bulbs and LEDs have been heavily promoted over the past years as the only environmentally ethical alternatives in lighting. Are they really all they’re cracked up to be? Do they stand to save power and, implicitly, money on your electricity bills? How much power do CFL bulbs actually consume?

To answer all those questions, and a bunch of extra ones, we’re going to take a look at what CFLs are, how they work, plus loads of other details. Read on, then decide if CFL bulbs are the way to go for you, your lighting needs, and your budget.

What are CFL bulbs?

Most people would be able to piece together the definition of a conventional light bulb. And most of us in the Western world have seen LEDs in use. But when it comes to CFLs, we seem a bit stumped by the science behind them.

the diagram of a cfl bulbs

Image source: EE Times

So here’s a bit of physics for you:

CFL light bulb definition and facts

How CFLs work:

Electricity runs through the tube, where it interacts with the argon and mercury vapor. This produces UV light, which, in turn, excites the fluorescent phosphor coating within the tube. Thus, visible light is made.

  • ‘CFL’ stands for compact fluorescent light, but these bulbs are also called energy-saving lights and compact fluorescent tubes.
  • CFL bulbs have been designed to replace incandescent bulbs, which is why many models fit inside the same fixtures as those in the latter category.
  • CFLs are made up of a curved or folded tube and a base, which comprises electronic ballast.
  • By and large, a CFL will use 20-30% of the energy required by equivalent incandescents. They will also last 8-15 times more. They do cost more but stand to save you 5 times their upfront price throughout their lifetime.
  • Remember that the number of Watts listed on the package of a CFL bulb represents the amount of electricity they consume, not what they emit (as is the case with incandescents).
  • CFLs do take a while to ‘heat up’ and become completely turned on. This process can last 30 seconds to 3 minutes. This is all the truer of CFLs with a globe or reflector-shaped cover.

Tips on how to best use a CFL:

  • Twist them in by holding the base (ballast).
  • Don’t constantly switch them on and off: keep them on for at least 15 minutes at a time.
  • Match a 3-way socket with nothing else but a 3-way bulb.
  • Don’t use them outside, if you live in areas with cold temperatures. Check out the optimal temperature on the package. Place them in open fixtures, to protect them from the environment.
  • Inside, only use them in open fixtures, because they will otherwise overheat and their lifespan will be reduced.

Are CFL bulbs dangerous?

The short answer is a definite “no”. If you’re looking for a more detailed explanation, find one below, courtesy of the National Geographic Energy Challenge blog.

CFL light bulb with a skull instead of a glass bulb

Image source: WordPress

Yes, it is true that CFL bulbs contain mercury. However, this doesn’t necessarily mean they are any more likely to (fatally) injure anyone using them. Yet this remains a concern, as some homeowners who have children continue to cite this reason for their refusal to upgrade their fixtures.

The fear that CFL bulbs are a hazard has been preposterously blown out of proportion—much in the same way this happened to thermometers. Check out what science has to say about this ‘threat’:

  • In 2008, science journal Environmental Health Perspectives published a piece on the actual mercury content of CFL bulbs. The figure sits at 3-5mg of mercury/bulb. That amounts to 1% of the mercury found in old thermostat models. And when a CFL bulb breaks, only a fraction of that mercury actually gets released into the air.
  • In 2011, a study published in the journal Environmental Engineering Science found that a broken CFL lightbulb, which doesn’t get cleaned up for as long as 24 hours, will only expel 0.04-0.7mg of mercury. According to the scientists, you’d have to leave a bulb like that for weeks before they reach a level that might pose a threat to a kid.
  • If you believe mercury is toxic, think of it this way: by using a CFL bulb, you’ll reduce the amount of power consumed on residential lighting. This, in turn, will drive down the amount of mercury that coal-fueled power plants release into the atmosphere. Pro tip: they are the biggest source of mercury pollution on Earth.

On the other hand, though, there’s a far more legitimate and science-based concern regarding CFL bulbs: they produce UV radiation. This has been proven by a 2012 Stony Brook University study. The research says that CFL bulbs that get damaged during production or shipping can emit UV rays.

How serious is this? How much should you worry about it? To be absolutely safe, the researchers who led the study cited above recommend using CFL bulbs inside enclosed fixtures, not staring directly into their light, and maintaining a distance of at least 11 inches from them.

How to dispose of CFL bulbs

Now that we’ve established that CFL bulbs are pretty safe to use, it’s also worth noting that they require some careful handling when disposing of them. To make sure you’re entirely on the safe side, you can always follow the clear rules of the U.S. Environmental Protection Agency (EPA):

  1. Ask everyone to leave the room. This includes guests, kids, and pets.
  2. Air the room. Open an outdoor door/window and keep it open for 5 to 10 minutes.
  3. Turn off the HVAC. If you have centralized heating and/or air-conditioning, make sure they’re powered off.
  4. Do not use a vacuum cleaner. Not only can the glass shards ruin your appliance, but it can also help spread mercury powder or vapor in the room. If you need to vacuum, because pieces of glass remain, make sure to do so with the windows open, use the hose on the spot where the bulb broke, and throw out all the debris in the vacuum bag.
  5. Prepare for clean– You will need the following:
    1. a piece of cardboard or hard paper;
    2. duct tape or any other type of adhesive surface;
    3. a wet cloth or other material, to wipe off the surface;
    4. a canning jar, Ziploc bag or any other recipient you can safely seal off. Note that sealable bags can still allow some vapor to get out.
  6. Clean thoroughly. Scoop the bigger pieces of broken glass with the cardboard, use the sticky tape for the smaller ones and the powder, and wipe the surface clean.
  7. After cleaning: put all the debris in sealed containers, in the trash, or an area out of the reach of kids and pets. Also, throw out all the cleaning materials, including the vacuum bag. Make sure there’s nothing left indoors and wash your hands with soap.
  8. Check with the authorities. In some counties and states, local authorities require all fluorescent light bulbs, be they intact or broken, to be disposed of in special recycling centers. If this is not the case where you live, simply throw everything out with the rest of your trash.

To keep these guidelines handy, the EPA offers a free version to download and print here.

epa cfl light bulb cleanup guidelines infographic

Image source: OPPD The Wire

Need some more pro tips on how to dispose of broken CFL bulbs? You can try taking them to Lowe’s or Home Depot because they recycle them for free.

Do dimmable CFL bulbs exist?

Only a couple of years back, most sources would resolutely tell you that you cannot use CFL bulbs with dimmers, controls, motion detection sensors, or basically anything other than a regular On/Off switch. That has somewhat changed in the meantime. Now, more manufacturers are producing dimmable CFLs, as well as dimmers specifically designed for CFL bulbs.

That being said, there are still many things you need to remember when using CFLs and dimmers together:

  • Non-dimmable CFLs should not be used with dimmers. Research hasn’t found this to be necessarily unsafe, but you would likely experience flickering and flashing.
  • Check the bulb to see if it’s marked as “not for use with dimmers.” Most CFLs are marked as such.
  • It’s best to use a dimmer specifically designed for CFLs and LEDs. Bear in mind that not all dimmers will support using several types of bulbs at once, on the same device. You should probably also spring for CFLs from one and the same producer, as performance and specs vary across the market.
  • You can use some CFLs with motion sensors. However, do bear in mind that using them repeatedly for less than 3 hours at a time will reduce their lifespan.

What are CFL grow bulbs?

As the Internet will be quick to let you know, many cannabis users craft their own hydroponic gardens. However, the issue is far from lacking in controversy, as some state CFL is trash, compared to HID. CFL grow bulb advocates argue for their affordability and ease of use.

If you’re thinking of using CFL bulbs to grow, check out these tips, facts, and pointers:

Legitimate reasons to use CFL grow bulbs:

  • You don’t have the space to use HIDs. These heat up a whole lot, and if you can’t afford a cooling rig (which usually involves having ducts installed and walls drilled), CFLs are a viable option.
  • You are not that committed to growing as to use HIDs. You only have a couple of plants.
  • CFLs are widely available, affordable, and fit in most fixtures. They can also be placed closer together than HIDs.
  • In time, you can come to use CFLs together with HIDs, if you figure out you want to expand.

hydroponic starer kit with CFL lights

Image source: Hydroponics Group

Types of CFL grow lights:

  1. Soft white – color temperature: 2,700K. This looks like an HPS light in terms of spectrum and should be used during the flowering stage. You can also mix several soft white CFLs with a daylight bulb during flowering, for more light and better results.
  2. Daylight – color temperature: 6,500K. This one, which resembles metal halide lights, is for the plants’ vegetative stage. Use these even if you’re using an actual HPS, not a CFL, for the flowering stage. They help grow the plant to 1ft, even on as little as 30W and don’t stretch the plants.

Avoid using bulbs that range between 2,700 and 6,500K as they can be next to useless for plant growth. Some 5,500K bulbs labeled ‘Daylight’ can be effective, but worse off than 6,500K.

Opt for bulbs that use at least 20W—but bear in mind that you’re likely to get the best results for big CFLs, 65W and over. Some of these oversized bulbs will require a special fixture, with a built-in compact ballast. A good rule of thumb is 100W per plant, with an additional 30-50W for extra grows. You will know that you need more light if part of the plant is shaded, with not many bulbs to speak of.

For good brands, try:

  • Lights of America – cheap, but pretty good;
  • GE or Philips – big, reliable brands, with more powerful products.

How to use CFL grow lights:

The only important thing to remember here is to set the lights up properly. Here’s how:

  • Have as much of the light facing the plant as possible.
  • Some bulbs emit more light on the sides than the front.
  • Distance is also crucial since CFLs are less intense and far-reaching than HIDs. The key thing to remember is that anything within 4-6 inches of the bulb will grow. Anything outside this sphere will not.

IMPORTANT: Don’t place the lights close enough to the leaves as to burn them. Even a 26W CFL can burn. Trim the leaves or use a fan and keep at least 1in of distance. If you plan on being away for a week, bear in mind that the plant will grow upward, toward the light, so anticipate this by elevating the lights.

  • You can also try LST, to put the CFLs within the plant.
  • Reflect as much light as the CFLs will emit, either with bright white walls, mylar, or reflectors.

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