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I have a lamp (from IKEA) that had a light bulb 3W 200lm 67lm/W 26mA I bought a light bulb that says 4W=35W 230LM Can I replace with that light bulb or even with higher watt? I mean is the only difference the electricity consumption or should I be careful of something else?

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    The light fixture should have a label on it stating the maximum wattage bulb that can be used safely.
    – SteveSh
    Nov 20, 2021 at 12:16
  • @SteveSh: The light receptor says: 100W. But next to it there is a label max 2x 35W halogen. (Has 2 receptors for lumbs). What does that mean?
    – Jim
    Nov 20, 2021 at 12:46
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    Halogens run hotter than tungsten, therefore the limit will be lower.
    – Tetsujin
    Nov 20, 2021 at 12:47
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    @Jim could you edit this info into the question please?
    – Nick Kennedy
    Nov 21, 2021 at 18:39

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The wattage limit on a light fitting is related to the amount of heat generated by a tungsten bulb of that wattage. Putting a 60W bulb in a 40W or 25W fitting is definitely not recommended.

However, your choices are both LED bulbs, which a) run cold & b) use a small fraction of the rated power. They give tungsten bulb wattage equivalents as people generally know approximately how bright a tungsten light is, based on this figure - so it's just a convenience for the buyer. People tend not to really think in lumens.
Therefore, there is no safety issue with using a brighter LED bulb.

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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – BMitch ♦
    Nov 22, 2021 at 19:20
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If you go from 3 to 4 or 9 or 10 watt LED bulbs in a fixture rated for 100W tungsten bulbs you will be fine. No LED bulb that fits the socket will overheat the fixture. However there is another consideration. If the fixture is closed, and especially if it has a small glass globe completely enclosing the bulb, you need to be careful when installing LED bulbs over about 13W because they create a lot of heat, nowhere near as much as a 100W halogen but enough that inside a closed globe the electronics in the LED bulb will overheat and the life of the bulb will be in months or weeks rather than years.

I've found that some LED bulbs in the 16 to 21 what range are so cheap and so bright, and I love the increased brightness, that I'm happy to change them frequently. In a fixture rated for 100W they are otherwise fine.

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  • If the fixture is closed, and especially if it has a small glass globe completely enclosing the bulb how does that look like? Could you link to an image?
    – Jim
    Nov 20, 2021 at 16:54
  • So the fixtures always specify the limit using tungsten bulbs?
    – Jim
    Nov 20, 2021 at 16:56
  • I think an image of an enclosed light fixture would confuse more than clarify because there are so many styles and they vary so much. If the bulb is inside a completely enclosed shade, cover, globe, etc ... if you cannot touch the bulb, in any way, without opening something, the fixture is enclosed. NO the limit is not always using tungsten bulbs. Recent fixtures may say "Max 9W LED" or "Max 20W CFL" and then you have to be. lot more careful. If it's an older fixture or if it does not say LED or CFL and the rating is for 40 or more watts, it is almost certainly for tungsten bulbs.
    – jay613
    Nov 20, 2021 at 16:59
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    @Jim Actually, many newer fixtures designed only for LED (or a few years ago, only for CFL) will be rated for LED bulbs. But it is a fairly safe bet than any ordinary fixture (as opposed to big warehouse lights or big outdoor floodlights) that uses a number 20W or more is talking incandescent and anything less is based on LED or CFL. In almost all cases if it has a small (LED or CFL) number, the type will be clearly stated. If it has a larger number then it may be older (incandescent was the only option just a few years ago) and therefore by default refer to incandescent.
    – manassehkatz-Moving 2 Codidact
    Nov 21, 2021 at 0:13
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You're fine. The 2x35 watt max is the maximum heat, 3.4 btu's per watt, so your 4w bulb outputs about 14 btu's per hour each. Your fixture is rated for over 200 btu's of heat.

It doesn't matter whether your watts come from LED's, tungsten, TV, coffee maker, or space heater. All put off 3412 btu's per kw/h. Watts are so directly connected to heat that some utility funded conservation projects no longer fund lighting retrofits for non air conditioned spaces if the space has electric heat since reducing the watts from lights will require increase cycle time for electric heat.

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  • I thought that 2x35 meant 2 light bulbs of 35W as the fixture supports 2 light bulbs. My 4W LED says 4W=35W. How come your calculations use the 4W?
    – Jim
    Nov 20, 2021 at 16:53
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    It actually uses 4W. The equivalence figure, as already mentioned above, is a consumer convenience figure, so you know how bright it would be if it were a tungsten bulb. That's all.
    – Tetsujin
    Nov 20, 2021 at 17:10
  • I edited to indicate heat for each lamp. The 4w=35w is their claim that the 4w draw of those bulbs puts out equivalent output of a 35w tungsten bulb, which is a bit overstated, these GE bulbs amazon.com/GE-Lighting-24782-280-Lumen-Candelabra/dp/B00A7MGH3A/… put out 9 lm per watt, which would be around 315 lm, so they are more like 26w tungsten (which overstastes energy savings).
    – NoSparksPlease
    Nov 20, 2021 at 17:21

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