More generally, one can't really talk about 'compatibility' in relation to only one characteristic of a product, since they might be incompatible in terms of other characteristics (like 12V and 230V lamps/bulbs with the same shape, size and base)!
Kind Regards, John
This is a real problem, specially with voltage, 10-30 VDC and 12 Volt 50 Hz would have as tungsten been to some extent interchangeable, but not with LED. But the big problem is size, to include cooling fins the LED is often reduced to 1" rather than 2" and so a completely different spread of light.
However the fluorescent is real problem, the wire wound ballast has been discontinued, so the fluorescent tube may be rated 58 watt, but actually uses more like 52 watt, and the lumen may be rated at 4600 but it is more like 5000, and the life is also increased due to using a HF ballast rather than the old wire wound. So the punter sees the LED tube at 22 watt and thinks that is a real saving, but instead of 5000 lumen he get 2100 lumen.
And we see 35 watt equivalent marked on a bulb, but the compact fluorescent came between the tungsten and the LED, and no way is that bulb equivalent to 35 watt compact fluorescent. Even as tungsten, the old pearl bulb gave a much better spread of light to either the clear glass quartz tungsten, CFL or LED.
The living room in this house had a single 100 watt tungsten bulb, which really was not big enough to start with, so moving to LED I have a chandelier with 8 x 6 watt LED candle E14 bulbs, so 48 watt and 2800 lumen has replaced 100 watt and 2000 lumen, it is slightly brighter, but not that much.
Old house had 2 x 100 watt so 4000 lumen new lights 10 x 5 watt and 4200 lumen. The problem is people today compare a rough service bulb and with rough service the lumen for 100 watt tungsten is 1500 lumen, but the old pearl 100 watt standard bulb was more like 2000 lumen.
The same with spot lights, the 12 volt spot was brighter than the 230 volt spot of same wattage, by using a regulated power supply the bulb could run closer to the limit, we all know with tungsten 12 volt was better, but look at the equivalent charts and they now show them to be the same.
I found LED bulbs with the base at top, do not seem to light the room as well as when in a chandelier with base at the bottom, the spread is so much better when reflected off a white ceiling. In my old house at bed head there were two GU10 spots for reading in bed, these did not normally light the room very well, which of course was the idea, just enough to read with, but turn them up to ceiling so light reflected off the ceiling and the room seemed twice as bright.
So if you were to swap in those bed side lamps between 35 watt tungsten and 7.5 watt LED to read with, it would not be far off being the same, but spot lights were never designed for general room lighting, so can't expect an equivalent chart to be any good when the lamp is not being used as it was designed.
