I had a 65W tube, the thick ones, now only 58W available, so rather than swap the ballast which would mean taking the fitting off the ceiling I went for a 24W LED tube. I bypassed the ballast so simple 230 volt at the pins at power end with a sticker on the fitting showing which way around to fit the tube. However no where near the amount of light the fluorescent kicked out, so then, a bit late, I started to look at details.
24W LED tube gives out 2400 lumen, but only 24 watt if the ballast is removed, you can leave ballast (if magnetic type) in place and replace the starter with a fuse, there is clearly a volt drop across the ballast and some power is required to basic just warm up the ballast, so lamp uses more like 45W if ballast not removed.
So next tried to find lumen per watt of a fluorescent tube, this is not easy as it depends on the coating of the tube and the ballast used. So at best around the 97 lumen per watt, but with magnet ballast could drop to 85 lumen per watt, but the LED tube is expensive so comparing with a HF electronic ballast seems in order as all new works out cheaper than LED even with an electronic HF ballast and life expectancy is about the same.
So to compare outputs a twin tube LED fitting is not quite the output of a single tube fluorescent with HF ballast and will cost around double cost of fluorescent, when it comes time to renew tubes, the fluorescent wins of course. There are some LED tubes with higher outputs, but they also cost a lot more.
However often we don't need the 5200 lumen typical output of a 58W fluorescent tube, all we need is the length so as not to cast shadows, in which case swapping a 58W for a 24W may work, but if you need the 5200 lumen then better to fit a HF fluorescent, yes only 95 lumen per watt not 100 lumen per watt of LED but cost of parts means the straight fluorescent tube is still king.
There is another problem with the LED, if an LED tube is replaced with a fluorescent without swapping starter and refitting ballast some thing must go pop. Be it the fuse that replaces starter, or the heaters in the tube, or the whole tube, something will go pop. With this in mind, after looking further, I think replacing fluorescent with LED is a bad move. I now realise I should have wired all 4 pins in series, the two pins not needing power on the LED tube are shorted out, great if wired in series, but if not then fitting the LED tube wrong way around is a direct short circuit. Really a sticker is just not good enough.
Nothing wrong with LED's as stand alone lamps, but there are clearly issues when used to replace a fluorescent tube.
2250/22 = ~102
