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I'm considering to buy full spectrum incandescent bulbs in the US, to be used here in Europe. Here these types of bulbs are rare, since it's mostly LED these days.

First I thought I needed to step down the voltage, for instance with a travel converter for the US market. But someone made a side remark to switch it in series.

I know a 120V bulb on 230V mains would instantly burn out. But from high school experiments I vaguely remember the series layout might actually work: put 2 bulbs in series and the 230V would be half: 115V. But what about the current?

Questions:

  1. Would 2 bulbs rated 120V/150W in series on 230V mains work?
  2. Would they glow (almost) equally bright as 2 bulbs rated 230V/150W in a parallel layout?
  3. Would it work with a dimmer?
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    In my opinion, the quality of the light from some LED lamps is just as good as incandescent. I can't tell the difference just by looking at the light. Just look for a low color-temperature and a high color rendering index (CRI).
    – mkeith
    May 16, 2019 at 15:37
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    Really just buy some higher quality LED bulbs and forget about dangerous ideas such as this one.
    – yo'
    May 16, 2019 at 17:41
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    Thanks for your suggestions. Indeed, LED has come a long way and the good ones are virtually indistinguishable from the incandescent bulbs. Most of them are rubbish in terms of light quality though, but I found suppliers that sell only the high-end stuff. Still, there don't seem to be LED bulbs available yet with high CRI that are also dimmable and flicker-free.
    – Rolf W.
    May 16, 2019 at 18:19
  • Lamps are cheap - just buy the right ones so you don't scare the next person to work on your installation.
    – Criggie
    May 18, 2019 at 1:01
  • Where in Europe? What you propose would be unlikely to meet the Wiring Regulations (Building Regulations Part P) in the UK.
    – Andrew Leach
    May 18, 2019 at 11:01

5 Answers 5

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Yes, that should work fine. Back in the day, Christmas lights were 6 or 12V lights in series and there were thousands of those sold each year.

A slight caveat is that typically the threaded portion of the socket is connected to neutral. The second light bulb will have voltage on the threaded part of the socket, so you should take precautions to make sure it cannot be touched.

Another slight caveat is that technically the 120 and 230V sockets are different. The American socket is called E26 and the European socket is called E27. However they are so close that in practice the bulbs seem to interchange just fine.

I am in the USA and purchased a number of 230V 100W light bulbs. We have about 135 volts in our house (normal is 120-125 but our transformer is a little different). I use them as night lights in the kids' room and in the bathroom.

The bulbs I have came from Croatia I believe. If your goal is purely to get incandescent light bulbs which are not available in the store anymore, there may be options to get 230V bulbs sent through the mail.

Good luck!

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  • Thanks, that would certainly be an important caveat to consider about the thread being hot. Our mains is AC here in Europe though, so it's alternating; I guess it wouldn't matter in that case?
    – Rolf W.
    May 16, 2019 at 18:51
  • It's a good way to get bit trying to change a lightbulb, +1
    – Mazura
    May 16, 2019 at 19:37
  • Yeah, come to think of it we still have a hot and neutral wire. And only one makes the voltage finder light up, so I guess it applies for AC too.
    – Rolf W.
    May 16, 2019 at 19:42
  • A slight caveat is that typically the threaded portion of the socket is connected to neutral. A lot of European plugs aren't polarized, so this is a non-issue.
    – Janka
    May 16, 2019 at 22:22
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    Alternating current doesn't matter in this case. In a standard bulb, the bottom has an alternating sine wave of power, while the thread wouldn't have any power to it. This isn't a "push from one end, then the other", it's a "push from one end, then pull from the same end".
    – user3757614
    May 17, 2019 at 1:57
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It is possible, as long as they use the same power (or resistance).

However, it comes at a risk. If one of the bulbs uses less power (for whatever reason, maybe damaged/end of light ... see Ferrybig's remark below for a good reason), the other uses more, and will break (faster), so it's not a perfect solution.

Because of P = V * I <=> 150 = 110 * I, I = 1.36 A for two bulbs, which is 0.68 A per bulb.

For the 220V way: P = V * I <=> 150 = 220 * I, I = 0.68 A per bulb.

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  • The bulb can only loose diameter of there filament over time. This would lower the current for the other bulb even futher, due to the higher resistance. How would a bulb manage to draw more power?
    – jusaca
    May 16, 2019 at 15:22
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    If the resistance of a bulb goes up, the voltage also goes up, if the bulb contains a varistor (for protection against power surges), it could kick by this increased voltage, and could potentially also trigger any varistor in the other light, leading to a cascade failure
    – Ferrybig
    May 16, 2019 at 17:17
  • @Ferrybig thanks for adding that comment, I added it to my answer.
    – Michel Keijzers
    May 16, 2019 at 20:24
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I feel that it is not a good idea as a standard practice. But conceptually, it would be fine to use two 120V filament type light bulbs in series on a 230V system. I have done it before, briefly, and the bulbs appeared pretty normal. So feel free to experiment. But in the long run, maybe the bulbs would not share voltage equally and one will fail prematurely. Not sure.

Yes, the brightness would be close to 2 230V bulbs in parallel.

Yes, it would work with a dimmer.

NOTE: This answer applies to filament-type bulbs (incandescent bulbs). It would not be a good idea to put LED bulbs or fluorescent bulbs in series because their internal electronics are not designed for that.

NOTE 2: I am not sure this is a big deal. Usually on a light bulb, the center conductor is "hot" and the outer, more touch-able conductor is "neutral". In series in a 230V system, one of the bulbs will have the center hot, and the outside at high voltage (half of "hot," or 115V). You could argue this is the tinyest bit more dangerous than standard 120V systems and bulbs. But as long as you don't touch either conductor it should be OK.

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  • Thanks, yes it's specifically for filament-type bulbs. Once LEDs with the desired specs become available I might change the wires of the fixture back to parallel and use LED instead.
    – Rolf W.
    May 16, 2019 at 18:32
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    I guess the dimmer would need to be rated 300W though, since the bulbs would be about as bright at 2x 230V/150W?
    – Rolf W.
    May 16, 2019 at 18:35
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    Each bulb will use (approximately) the same amount of power as it would if it was plugged in to 120v on its own. So yes, the dimmer should be rated for twice the power as the individual bulbs.
    – pbfy0
    May 16, 2019 at 18:55
  • The note about filament bulbs was not intended for OP specifically. OP's question was quite clear. But answers at this site rank high in search results, and I wanted to make sure my answer addressed that important issue for those who don't read the OP carefully.
    – mkeith
    May 16, 2019 at 21:45
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In theory, if it's really no electronics bulbs, you can do this. The lifetime of the bulbs may be lower as they need not divide the power equally as they age, and larger power means larger wear.

In practise, yes, it will work and will do what you expect. Unless something goes wrong.

Still, it's very likely against the electricity code in any European country, as your bulb is a device rated probably for 100--120 V, so it can never be connected to 220/230V mains. And there are good reasons for this as there are safety issues: Imagine you (or anyone else that happens to be staying in your house, even just for a visit) replaces the bulb with a 220V one, or even a 120V one with different wattage. Then you will expose one of bulbs to >120V, and they were not rated for this. Second, you should not wire this yourself and a certified electrician should never be willing to do anything like this. Also note that if you had an accident, the insurance company would likely claim you responsible as in their point of view, you would have been simply messing up.

You are solving the wrong problem. Just invest into some high quality LED bulbs, they need not be expensive. You can get 600-lumen CRI 80 LED bulbs for as low as EUR 2. Is it really worth messing up with the electricity?

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  • Could anyone comment on whether or not this is indeed dangerous, like yo' implies? Based on the other answers the risk seems to be primarily inconvenience and the cost of a lost bulb or two.
    – Rolf W.
    May 16, 2019 at 18:29
  • I'm not planning on changing the house's wiring, by the way. Just that of the light fixture.
    – Rolf W.
    May 16, 2019 at 18:29
  • It used to be (And to some extent still is) common practise in the entertainment industry to series lamps in light curtain and blinder arrays. These were anything from pairs of 500W or 1kW 120V PAR right the way down to arrays of 9 28V aircraft landing lights, I am not aware of anyone having a safety issue (The pain in the arse was figuring out which one had failed).
    – Dan Mills
    May 16, 2019 at 20:31
  • It looks like the OP would want something substantially better than CRI 80 if they are after a full-spectrum lamp.
    – Andrew Morton
    May 17, 2019 at 16:57
  • @AndrewMorton CRI 90+ are also available (about a double price though), if anyone thought 80 were not enough.
    – yo'
    May 17, 2019 at 17:42
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Yes, it's not Code legal (because the shell of the upper bulb socket will be hot), but it will work. This depends on the bulbs being equal; if they're not, one will burn out first.

However, given the Code violation and the general difficulty, I think you're barking up the wrong tree. Fluorescent technology has gotten absolutely fantastic in its sunset years, and there's no problem getting full-spectrum fluorescent tubes at any color temperature you desire. The light is higher quality than is possible with LED (really).

The tube doesn't need to be compatible with one mains voltage or the other; that's the ballast's job. And two things are true about ballasts. First, you can get native European ballasts for standard fluorescent sizes. Second, modern North American ballasts are multi-voltage compatible from 110-277 volts, and 230V is in their midrange.

It's also vastly more efficient, with lumen efficiency near LED, so the additional up-front cost will be paid by your reduced electric bill.

You can also explore LED options, but there's an ocean of fair-medium quality out there, and top quality LED is still pretty hard-to-find and boutique priced.

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  • One caveat with multi-voltage fluorescent ballasts is many of them have a "Non Consumer" Part 18 FCC certification, which means they are not held to quite the same emissions limits and standards as a consumer Part 18 device is, and thus may not be legal for residential use. (It is unclear from 47 CFR Parts 15/18 of the legality of this situation; if it is legal, than the ballast user is on the hook for any RFI it may generate)
    – ThreePhaseEel
    May 17, 2019 at 4:03
  • If OP is using them in Europe, US code is not relevant. Moreover in many European countries lamp connectors are 2 conductor (no earth) and reversible, so the thread has a 50% chance of being hot anyway. Typically they rely on double insulation for safety.
    – abligh
    May 18, 2019 at 8:02
  • @abligh I don't recall mentioning US code. The European types you mention do a pretty good job shielding both terminals. OP's premise is bringing bulbs from the United States, and those types are exceedingly rare in the US - almost all are different sizes of Edison base.
    – Harper - Reinstate Monica
    May 18, 2019 at 13:40
  • @Harper to my knowledge "code" is mostly used in the US and in much of Europe you can happily wire what you like (professional electricians do have standards). Edison screw is relatively common in Europe (in various sizes). I believe every lamp in Ikea is Edison screw for instance - certainly all mine are.
    – abligh
    May 18, 2019 at 16:36
  • @abligh "my territory doesn't have electrical code" - what you mean is "I've never seen an inspector in my life, and have always gotten away with it so far". That may well be, but they do exist. And that can eventually catch up with you - when you sell your house (USA), when someone gets hurt, this, etc. Somebody in your government thinks electrical safety is his bailiwick. And his reference standard for "competent work" will be some competent author's Code book.
    – Harper - Reinstate Monica
    May 20, 2019 at 15:15

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