I have moved this here as it was located in a thread which was about SLI lamps. it is more appropriate for it to be in this thread.
Although I was aware of the info from the Lamptech article - it was this war time prudence in designing the 5ft 80w tube that would lead to its demise from streetlighting service by the 1970s due to the relative inefficiency of the 5ft (and 8ft 125w tubes). I wonder if the Europeans rated their tubes the same as the British in the 40s and 50s or went straight to the optimum rating for a 5ft T12 tube of 65w and 100w for a 8ft tube?
A 5ft (1500mm) T8 tube is of course rated at 56w nowadays and with modern phosphors the light output will be far greater than its wartime equivalent.
It is has also just clicked (it's been a long week - it feels half like half past Thursday when its really only quarter to Thursday..
) why I remember as a kid seeing fluorescent tube starters marked 65/80w and 100/125w. I never actually saw a 80w 5ft tube they were always 65w and likewise 8ft tubes were always it seems 100w. The starters were of course marked for the older lamp rating which I guess, as Lamptech states, were still around in the 1970s. Do modern glow starters still have these "older" ratings on them? I don't have one to hand.