In my house, I currently have a mix of incandescent, CFL, and LED bulbs. I have a supply of additional CFL and LED bulbs. My immediate plan is to go through the house and swap out the incandescent bulbs that I can since they're considerably less efficient, and aren't really much of a change in investment, but I'm less certain on switching from CFL to LED since they're only a year or two old, might be good for years more, and contain more harmful elements for the purpose of disposal.

Does it make sense to replace them at this time? Financially and for the good of the environment?

  • 3
    My gut instinct is "no". The difference in real-world efficacy between CFL and LED is relatively small, and LEDs are constantly improving. I'd wait for them to get through their lifetimes before replacing. When you do replace, whenever that is and whatever you replace with, make sure the CFLs go to a recycling facility to avoid the Mercury ending up in landfill.
    – Flyto
    Jan 15, 2016 at 7:40
  • Most articles I skimmed suggest that one should replace even good CFLs with LEDs under many circumstances. Since this is something I asked myself too recently, I'll try a detailed answer later.
    – mart
    Jan 18, 2016 at 8:12

3 Answers 3


To answer your question about whether or not it's financially worthwhile to swap them out, I looked at two simlarly rated lamps from the same manufacturer:

So there's a 3W difference in power consumption between the two.

If you keep the light on for 4 hours/day every day for a year, it will consume around 4KWh of extra power each year, or around 60 cents worth of power at $0.15/KWh.

The CFL is rated for 8000 hours, so if it's brand new and lasts the entire 8000 hours, it will run for around 5.5 years, costing you an extra $3.30 in electricity. Similarly, if the lamp is already a few years old and has only 2000 hours left it'll cost you less than a dollar of extra electricity.

Unless you can replace the CFL with an LED for less than $3.30, it's probably not going to be financially worthwhile.

Your payback period may be different depending on how often you use the lamp and how much you pay for electricity. I ignored the labor costs of changing bulbs since in most cases it's minimal, but sometimes may be significant -- I have a set of 4 stairway lamps that are mounted high on the wall and I need to bring in the long folding ladder and set it up on the stairs to reach the bulbs. When one of the CFL's burnt out, I replaced all 4 with (hopefully longer lifetime) LED's at the same time since it was easy to replace them while the ladder was set up. It takes me around 30 minutes to get the ladder from the garage, set it up, then put it away again, so if the LED really does last 3 times longer than the CFL, it's economically worthwhile for me to change it out before the end of life of the CFL.

And as others have said, due to the sunk environmental cost in creating the CFLs you already own, it's likely a net environmental loss if you discard them before their useable lifetime is over.

  • I think the greatest benefit from LEDs are when you are on a power budget and need to keep your energy consumption down at all costs. I.e. For example off the grid applications.
    – Escoce
    Jan 21, 2016 at 18:48
  • If you're so power constrained that a few watts makes a difference, you probably ought to look at low voltage DC lighting that you can power directly from your batteries so you don't have inverter losses in converting to 120VAC.
    – Johnny
    Jan 21, 2016 at 20:46

At present it is not sustainable. There isn't enough difference in efficiency. All bulbs have Hg according to Wikipedia, but 'eco friendly' have less.

  • Jonny's comment prompted a check. "Eco friendly" bulbs have about 1 mg Hg/bulb. The common bulb has about 5 mg. Coal report from the Pembina group cited 20 to 33 mg/ MWh (1000 kWh) So a eco bulb that uses 10 W over a 10,000 hour life will result in twice as much Hg from the power it uses compared to the mercury inside. Compared to an incandescent bulb it delivers far less Hg to the environment, even if not properly recycled. (Based on coal fired power) *

According to this article the minimum daily does of Hg to have a demonstrable effect is 300 ug (microgram)/day. You need to EAT two eco bulbs a week to get this dose. (And the exposure refers to methylmercury, a much easier to absorb form)

Overall, worrying about Hg in bulbs right now is a case of rearranging the deck chairs on the Titanic. Take them back to a recycling station if you can, but don't stay awake if one slides into the trash. And if you use coal generated power, then CFLs are are better choice than LED

LED lights right now are seriously over priced. But the tech is changing fast. Once you have installed your last CFL bulb, check out the current state of the art before buying more replacements. If you are currently all incandescent, then by preference replace with LED, 2nd choice CFL.

(In passing: Living rurally they don't last any 10,000 hours. We lost 4 in a day due to a voltage spike.)

  • Are any CFLs 100% mercury free? I couldn't find any with a brief Google Search. I've seen some sold as "low mercury CFLs" (which seem to use 1mg of Hg instead of the typical 3 -5 mg of standard CFLs, but I haven't seen any that are completely 100% mercury free (afaik, the mercury vapor is an integral part of how fluorescent bulbs work). These low levels of mercury aren't as dangerous as many people think, but they still need to be disposed of property (and cleaned up properly after a break).
    – Johnny
    Jan 19, 2016 at 0:40
  • That doesn't really answer my question - do you have a source to back up the claim that some CFL's contain no mercury?
    – Johnny
    Jan 19, 2016 at 5:10
  • Edited answer to reflect your concern. thanks for the correction about zero hg bulbs. As mentioned above. The best I can find is 1 mg/bulb, cited in Wikipedias article on CFL bulbs. Jan 19, 2016 at 5:12
  • It sounds like you're making the point that the mercury level is so low that it doesn't matter, which is not the same as saying that some CFL's have no mercury at all.
    – Johnny
    Jan 19, 2016 at 23:12
  • hence the edit in my answer. Jan 20, 2016 at 20:11

Right off the bat, I would say that LEDs make much more sense sustainability wise since CFLs contain Mercury which makes broken CFLs hazardous waste!

I will see if I can hunt down figures for embodied energy, and energy consumption to do a more thorough analysis. I will update the answer when I have found those figures.

Also, do you pay to heat your house? If so, then DO NOT ditch those incandescent bulbs. All of the wasted energy is in the form of Radiant heat. So if you heat your house anyway then those incandescent bulbs are already 100% Efficent!. Just switch them out for the LED bulbs during the summer.

  • 3
    But if he already has CFLs, the hazardous waste part (which is only a problem if no recycling facilities are available) is irrelevant. And re the heating thing, no! First off, direct electrical heating from the grid is the least efficient way to heat a home - if they have gas or oil (or heat pump) heating, this is much better. Secondly, even if heating is via electric heaters anyway, light bulbs will mostly heat a layer of air under the ceiling - or, in recessed down lights, heat the void above the ceiling. Make the lighting efficient, and use efficient heating too.
    – Flyto
    Jan 15, 2016 at 7:43
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    Sure use what you have first, that is always preferable. He ALSO has LED bulbs! The hazardous waste part is not irrelevant if you recycle CFLs. If you are purchasing bulbs then you are increasing demand for a product that has toxic materials and most of the public will throw in the trash! Nobody exists in isolation, everything is connected to everything else! Jan 15, 2016 at 19:06
  • Incandescent Lightbulbs will NOT HEAT THE AIR. The heat produced is in radiant form, which means that it heats everything that the light touches. Radiant heat IS LIGHT in the infrared spectrum! Jan 15, 2016 at 19:08
  • Well, some of it heats the air by conduction (and the resulting convection). Some is radiated, and it then mostly heats the ceiling :-P
    – Flyto
    Jan 15, 2016 at 19:09
  • I have done the math on this before, looking at embodied energy, energy consumption, and material use. I will hunt that down and modify my answer to include the math. It boils down to, if you are heating your house use Incandecent, if you are not then use LED. And only use CFL if you already have them! Jan 15, 2016 at 19:10

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