Please don’t use incandescent bulbs for heating



So as Andrew Leonard writes in his “How the World Works” blog, this all began with a column by

Toronto Star energy reporter Tyler Hamilton that itself had summarized the conclusions of a study raising questions about whether it always makes sense to replace incandescent light bulbs with CFLs. The nub of the argument was that in some cases the heat generated by the incandescent light bulbs could be useful.

Tyler is a friend of mine and a great reporter, so I sent him an email explaining why this is not true, which was not written for publication. Then Leonard himself summarized the column on his blog. So, as Leonard explains:

This excited a storm of comment, and even inspired Joseph Romm, author of “Hell and High Water: Global Warming — The Solution and the Politics,” energy expert, blogger extraordinaire, and regular Salon contributor, to pass on a copy of an e-mail he sent directly to Hamilton.

[That Leonard comment is, I believe, the blogging equivalent of make-up sex — note to parents, that link is PG-13 — but I digress.]

Anyway, here is my email:

From either an energy or a CO2 perspective, incandescents are a big loser. If you really like electric resistance heat, buy the best portable forced air heater — it’s is still infinitely better than using an incandescent for heat from a CO2 perspective. It doesn’t really matter what the source of your electricity is, since energy around Canada and North America is fungible (and we don’t yet have an oversupply of zero carbon electricity).

But again if you really prefer heating your house with electricity because you have zero-carbon electricity, then buy an electric heat pump — if you have one, then dump your incandescent, the heat pump is much more efficient. For a new home or gut rehab, get a geothermal heating and cooling system. Plus better insulation of course.

This is especially true if you do any significant amount of air-conditioning during the year — which certainly most commercial office buildings do in Canada — and I’m guessing many people run air-conditioning in your homes in Toronto during the summer (certainly that will become more common thanks to global warming).

I can assure you that if you were to do the life-cycle analysis in detail, you’d find that keeping incandescents for the heat value is an energy/climate loser.

Leonard also notes

A similar argument was made in a prominent letter to the editor published in the Star on Saturday.

(Incidentally, a very nice life-cycle analysis comparing incandescents to compact fluorescents can be found here. The answer: CFLs win.)

The bottom line: As traditional incandescents get phased out and replaced by CFLs, LED bulbs, and more efficient incandescents, don’t get all hot and bothered. They had their moment to shine.

34 Responses to Please don’t use incandescent bulbs for heating

  1. Ken Levenson says:

    Where do these guys come up with this stuff? Tortured logic?
    It’s like saying we should heat the house with gas cooking oven ….or perhaps the golden oldie: ketchup could be a vegetable…
    (hint: to my mind it’s the same kinda logic as the tobacco industry. you know… smoking’s good for you, makes you sexy, you feel better about yourself!) okay, I’ll stop now… ;)

  2. outerspace says:

    Radiant heat (infrared) from a lightbulb feels better than space heater convection heat. Halogen works better for this than incandescent.

  3. Traciatim says:

    Here is the trouble with your argument however.

    You claim that “From either an energy or a CO2 perspective, incandescents are a big loser. If you really like electric resistance heat, buy the best portable forced air heater — it’s is still infinitely better than using an incandescent for heat from a CO2 perspective.”

    Where do you get your light from out of a forced air heater? Your argument leaves you in the dark.

    The choice in the winter if you need to heat your home is clear. Switching to the CFL is a zero sum transaction since the heat lost from the table lamps incandescent bulb will have to be made up from your heating system. Only in places where air conditioning is running will you gain in energy from the CFL since the conditioner will run less because you have both light and less heat in the room.

    This would mean you should be using incandescents in the winter because they don’t contain toxic chemicals and CFLs in the summer in most of Canada. Though only in not enclosed lamps, and only inside.

    The whole thing is simply just too complex for average people to keep up with the information. The best thing they can do is stop buying bottled water shipped half way around the planet, eat less meat (not no meat, just not 30oz steaks all the time), buy local produce in season . . . FAR better returns than replacing all your lamps with CFL.

  4. Ken Levenson says:

    Feels better? We are doomed….

    You get your light from an energy efficient light and you get your heat from an energy efficient heater. I don’t know of any device that does both. (maybe the sun?)

  5. pmagn says:

    Problem I have is that I keep breaking CFLs, Also a number of them have died withing a year of operation. So that adds some more complexity to the equation – typical life cycle….also did that analysis take into account prober disposal of the bulbs and recycling of either one?

  6. Traciatim says:

    Well . . . other than an incandescent bulb . . . 90% of the energy is produced as heat (or there abouts) so from a 100Watt bulb you get about 1700 Lumens and 90Watts of heat. From the 25Watt CFL you will get about the same light output, and I’m not sure about the heat waste. I couldn’t find stats on it, but let’s just say it’s about 12.5 Watts.

    So in an 18 x 12 room that you are lighting with 4 100 Watt bulbs (two overhead and two table lamps) you are actually putting 360Watts of heat in to the room simply by lighting it. Since you are probably lighting it only when you are in there, it is basically a space heater.

    So you can either buy:
    1) 4 Incandescent Bulbs, cost: 2 bucks


    2) 4 CFLs and a 300 Watt space heater, 4 bucks for the lights and 50 bucks for the space heater.

    Now granted, it depends on your use of each . . . in the summer you put away the space heater in most climates, but you can’t with the regular bulbs. You’ll arguably replace the CFLs less, but I don’t find that to be the case in my house, maybe I’m justgetting bunk CFLs but for 10000 hours and having lived there only since last april I would think none would be down . . . I guess I expected the manufacturers to be honest.

    So just like any tool, they have their uses (and yes, where applicable I DO use them), but outside their uses other tools may be better for the job. In my hallways, in the workshop, over the dining room table . . . but not in a reading light that goes over your shoulder, or in the kids rooms that go on and off 17 times an hour ;)

  7. Joe says:

    Analysis not quite right. No form of heating is more inefficient than electric resistance heating, especially in a light bulb. Plus most people need more heating at night, esp. where they sleep. You sleep with four lights on?

  8. Traciatim says:

    No, we don’t sleep with the lights on (except for night-lights for the 3 year old to get to the bathroom . . . LED). Though in the winter when it’s getting dark at 6PM we do use the most lighting. The argument really is about which is better when you are heating your home, a CFL or a ‘normal’ bulb.

    So once again the problem is so complex than any normal person on the street can’t make a real informed choice with simple information. There are far too many factors involved in the decision.

    So we’re back to my original point, light your house with what you want and the best thing they can do is stop buying bottled water shipped half way around the planet, eat less meat (not no meat, just not 30oz steaks all the time), buy local produce in season. Oh . . . and stop buying all that crap you don’t need.

  9. In terms of what everyone else should do, your answer makes sense.

    Personally, my house, which is insulated to an R-32 standard, needs all the lights on several days a winter to reach 55 degrees. And I sleep best at about 32 degrees.

    I can’t imagine, though, that legislators will fail to mandate the change, which will be paid for by the individual homeowner and please the environmental groups.

  10. Joe says:

    The problem is NOT complex. It is much, much easier than, say, picking a wireless provider or health care plan. In terms of complexity, I would rank it as equal to, oh, I don’t know, sharpening a pencil:

    If you care about the environment or your energy bill, don’t heat your home with light bulbs. If you don’t, I suppose you can do whatever you want. That’s what made this country great — and the biggest cumulative contributor by far to the planet’s self-destruction.

  11. Paul K says:

    You sure do enjoy knocking down straw men. No one is advocating electric light bulb home heating. The question is, in cold winter areas, how much of indoor heat generated by incandescent bulbs must be done by natural gas and heating oil if CFLs are used? That the study cited is counterintuitive doesn’t make it wrong. Quoting the article:
    So switching to CFLs would, for millions of households, mean using less clean electricity and more natural gas to make up for the lost heat. Based on this crude analysis, it would suggest Ontario households should continue to use incandescent bulbs during the coldest winter months if the province is truly interested in lowering its greenhouse gas emissions. Ivanco says. “I practice what I preach. All of my exterior lights are compact fluorescent and I switch our interior lights to compact fluorescent ones only in the summer.”

  12. Ken Levenson says:

    Paul K,
    It’s not wrong because it’s counterintuitive. I believe it’s wrong because incandescent is a terribly inefficient way to provide light AND to provide heat. It’s like using your oven. Much more efficient to use your microwave to cook. But what about the lost incidental home heating the oven provides you ask? I think the saying is, “good money after bad”. Loose the incandescents… I think it is simple.

  13. Joe says:

    The article is dumb.
    You can heat your house with an electric heat pump. Also, heating with natural gas is quite OK. It beats wasting zero-carbon electricity. Energy is fungible.

  14. Paul K says:

    The article is dumb only if you can refute the study’s finding that using incandescent bulbs during the coldest winter months and CFLs in warm months lowers net greenhouse gas emissions

  15. Pangolin says:

    The article is dumb. The bulbs aren’t free of climate costs in manufacture and handling the bulbs is the most likely breakage point. I have never had a CFL explode on the fixture unlike incandescents; they break when you move them about. Plus they are hard to store as they shatter if they get jarred.

    There are many other better ways of heating a living space than using electrical resistance heating. Geoexchange heating is the most obvious in cold climates as the savings in cost and energy use are substantial wether your power comes from hydropower or “cheap coal.” Of course the sun shines on most buildings most days so that some kind of greenhouse and thermal storage should be a consideration for any building owner. A sunroom saves substantionally on heating costs.

    This kind of misinformation is yet another attempt to muddy the water and maintain market share by polluting industries.

  16. Valuethinker says:

    Actually the point is well taken.

    CFLs won’t save as much energy as we think, because the offset will be increased heating load (mostly more natural gas being used).

    This is a significant factor in Ontario, where air conditioning runs maybe 10 weeks a year, but heating runs 6 months+ a year.

    An incandescent bulb converts all of its energy to heat (a small amount to light) with basically 100% efficiency. *however* the conversion of fossil fuel to electricity is only 35-60% efficient (35% old coal fired station, 60% the most modern gas-fired one) and then there is 8% average transmission loss. Oh and you get illumination as well.

    Of course in summer the effect is reversed (if you have air conditioning) and by a considerable fraction because AC is inefficient.

    Ontario Hydro is pushing CFLs as an alternative to building new power plants, but the overall consumption of energy may not be less.

    Turn to the alternative: for 60%+ homes in Ontario, gas.

    A *modern* gas furnace is 90% efficient. But many in Ontario will be much older (50% efficiency say). You lose some energy compressing that gas in Western Canada and moving it 3000 miles down a pipe (a similar problem, of course, for a gas-fired power station). Say 10% loss (but the same either way you do it). If it is Liquid Natural Gas, shipped in from Trinidad & Tobago or the Middle East, the energy loss is more like 30-40% for liquefaction, regasification and shipping costs.

    Ontario is 40% nuclear power, though, and c. 20% hydroelectric (the balance being c. 10% gas and the rest coal or coal-generated electricity imported from the Ohio Valley and Michigan).

    So if you happen to use your incandescent lightbulb, in winter, when it is powered by nuclear or hydro-electric power, it will be emitting less GHG than the alternative of using gas heating (or fuel oil, or propane, or even wood, which are the other major alternatives in Ontario).

    (another small offsetting factor is that hot air rises, so an incandescent bulb doesn’t put much heat where the people want it. Offsetting the other way (my parents’ house) the bulb happens to be relatively close to the thermostat, and so it actually lowers the house temperature by confusing the thermostat).

    Note the geothermal/ground source heat pump option is not feasible for most Ontario homeowners, who lack the large gardens you would need, or the kind of soil you can vertical bore 50′. Let alone the $10-15k capital cost.

    The point is not that Ontario Hydro (or its successor companies) should give up on encouraging CFLs, because it is a summer peak utility, and that peak power comes from coal-fired stations in the US Midwest.

    But the gains from energy conservation, due to these complex interaction effects, have probably been overstated.

  17. Paul K says:

    Read the article. It says “If all homes in Quebec, where most electric power comes from non carbon sources, were required to switch from (incandescent) bulbs to CFLs, there would be an increase of almost 220,000 tonnes in CO{-2} emissions in the province, equivalent to the annual emissions from more than 40,000 automobiles,” the paper suggests. How can that possibly be twisted into yet another attempt to muddy the water and maintain market share by polluting industries.

  18. Peter Wood says:

    Here’s a way to warm yourself that is much more efficient than incandescent light bubs, heat pumps, or lighting the gas oven:

    Put on an extra jumper, or throw some extra blankets onto your bed!

  19. Ed Davies says:

    Paul K, I think you’re missing the point that if somebody in Quebec uses CFLs and therefore also uses a bit more natural gas the hydro generated electricity they would have used for incandescent heating will instead be used elsewhere in North America eventually reducing production of electricity by coal which would have produced more CO₂ than from burning the natural gas.

  20. paulm says:

    I still am not convinced about the total life cycle green cost too. It must take much more energy to dispose of CFLs properly.

    The best solution of course is not to have central heating…that is a luxury…I remember the days…my gran use to just heat one room in the house. When you went to bed you took a hot water bottle to heat the bed up before getting in.

    We are deluding ourselves if we think we can get away with reducing CO2 to 0 or close to without returning to practices like that.

    Of course this maybe coming sooner than we think with peak oil here…

  21. paulm says:

    Oh and of course the only lights on would be a couple of 40w ones in that room….

  22. john says:

    Paul K:

    The article is stupid, but it is also “clever” in its most negative sense. As Ed Davies and Joe point out, electricity is fungible and Quebec is tied into a large grid that uses some no carbon energy, some low carbon energy, and a lot of high carbon energy. So if you use light bulbs to heat, that’s so much no carbon energy that can’t be used elsewhere.

    And the extra carbon generated, say in Ohio, that otherwise might not have been generated? It ends up in Quebec’s atmosphere because it’s all one atmosphere.

    And, of course, that warms the atmosphere further whether you’re in Quebec, Ohio, or denial.

    Get it?

  23. paulm says:

    heres the dilemma…were using way too much energy, but were absolutely hooked on it…

    We have Germany predicted to run out of power this summer because there aren’t enough power stations…,2144,3157304,00.html

  24. Paul K says:

    For the record, we use CFls for most of the lighting in our house. Since in Illinois most electrical power comes from coal powered plants and our house has natural gas fired radiant hot water heat, there wouldn’t be a net CO2 benefit to using incandescents in the winter as described in the study. I just read the original article for the third time. Most of the criticisms here are off point and make me wonder if the critics have read the article before commenting. The fungible nature of electrical power argument is valid but may not apply. The article states Quebec uses primarily non carbon electric power. Assertions otherwise without facts and figures do not refute the study’s claim of a possible added 220,000 tonnes in CO2 emissions. In addition, one might assume that the time when Quebec does use dirty grid power would be the hot summer months, exactly when the authors of the study recommend using CFLs!

  25. Valuethinker says:

    Paul K

    Unclear. Peak waterflow in Quebec is spring, but summer waterflow is pretty good too.

    Quebec has a January power peak, not a July one.

    Quebec’s grid connections are to New York and New England, primarily.

  26. Robert says:

    The point most posters seemed to miss is that eletricity is a really bad way to generate heat, period. Due to the limitations of the Carnot cycle it is virtually impossible to achieve better than 50% efficiency and in practice much lower.

    “The national average thermal efficiency of power generation from fossil fuels in 1999 was estimated to be 32.54 percent, slightly higher than the previous year’s average of 32.42 percent.”

    Factor in transmission losses and you are lucky to get 25% of the original heat from the coal delivered as heat to your house. The argument as to what device you use to convert it is irrelevant as all such devices are 100% efficient (if you can call converting the highest form of energy into the lowest efficient).

    As several people pointed out it matters little whether your local source of electricity is hydro or not. It is a fungible commodity so each extra kwh involves burning more coal somewhere (as all the hydo gets used anyway).

    Conclusion – use CFLs to light your house. Insulate your house to the highest possible standard then use gas locally if you can’t find something better. We have used a wood burning stove for the last 3 years and don’t use the gas C/H at all.

    p.s. Why do we hardy souls in the UK appear to not need A/C whereas everyone in N America thinks its a necessity?

  27. Paul K says:

    Nowhere in the article, the study, this post or comment thread has any anyone said electricity is good for heating.

  28. Robert says:

    Paul – I disagree. There seems to be some sort of disjointed discussion in the early posts about whether it is better to use incandescents, blow heaters or CFLs – on the basis that their waste heat isn’t really waste at all!

    The comment in the article didn’t help:

    “From either an energy or a CO2 perspective, incandescents are a big loser. If you really like electric resistance heat, buy the best portable forced air heater — it’s is still infinitely better than using an incandescent for heat from a CO2 perspective.”

    An electric forced air heater is no more efficient than an incandescent bulb. They both convert 1KWH of electrical energy into 1KWH of heat energy. And both waste about another 3KWH in the power station and transmission lines. The correct strategy is to minimise use of electricity, use it only for those applications where there is no alternative and use the most efficient device available. For light generation that is a CFL, or better still an LED device.

  29. Paul K says:

    The quote from the post is by Joe, not from the article. Joe, either because he misread the article or to set up a straw man, was the source of the light bulb heat canard that had no relation to the contents of the article. Joe was not really recommending electric air heaters and those who thought he or the study did were down the garden path. I think you’d agree that CFLs are an interim technology on the way to LEDs. This post has touched on a little discussed question. Where, in a zero CO2 world, will the energy come from for heating?

  30. Robert says:


    “Where, in a zero CO2 world, will the energy come from for heating?”

    Mostly from insulation and conservation. We were asounded by how much difference it made after we installed cavity wall insulation and 270mm loft insulation. Despite being double glazed the windows are now the main source of heat loss, but in the evenings with the curtains shut we can easily keep the whole (detached) house at around 21 deg C with one fairly small log burner, even when it is -5C outside.

    Houses can be built – and are in places like Germany and Sweden – which require no heat. By hyperinsulation and careful heat management there is no need for any form of heating.

  31. Mike says:

    If I can extract a lesson from this whole dialogue it’s that small, measures in the area of energy efficiency SOMETIMES and IN SOME CONTEXTS do not yield the benefits they are supposed to. If we are serious about energy efficiency, it is going to take some more ambitious measures and/or some more context sensitive measures.

    If you have low or no-carbon electricity and mostly oil and natural gas heating, it makes sense to start incentivizing the use of electric heat pumps and especially ground source heat pumps. Yes, it is expensive but in the long run if you want to reduce carbon dioxide that is going to do a lot more than CFLs.

  32. Mike says:

    Yes, also passive houses like Robert says above with air-to-air heat exchangers. Insulation…more expensive and more thought involved but much bigger energy savings. In places with low space conditioning needs, lighting starts to play a bigger role and CFL use will have a bigger impact.

  33. charadeur says:

    People. Many of you are confusing watts with BTUs. Sure 90 watts of a 100 watt bulb goes to heat. But it is very inefficient way to heat your living space. Fist off there is no forced air to distribute that heat. Second hot air rises and because lights are normally higher in the room the heat just goes right up to the ceiling. A 100,000 BTU furnace at 80% efficiency puts out 80,000 BTUs. A 100 Watt light bulb puts out 341 BTUs. That is a drop in the bucket even if you have a way to force that heat out into the room vs. just being wasted at the ceiling. Sorry but it is dumb to think you are saving money by heating your house with light bulbs. Chances are you are making no difference in heat and just wasting the electricity.

  34. Chris W says:

    New LED traffic lights in North America now need to be replaced because in wet snow they don’t run hot enough to melt the snow off. This is causing accidents (although people should treat it as a 4 way stop instead of plowing through intersections). There are advantages to heat from an incandescent bulb.