| The F36T8 could not be popular in the US, as they were never intended for that market.
When the krypton became affordable for lamp production, in the US were already popular RS ballasts, what are quite sensitive for lamp parameter match. As krypton bring in the necessity of thinner tubes (to boost up the arc voltage) and that mean increase in striking voltage, a compatibility could not be maintained with existing F40T12, so lamps would require new ballasts anyway. So then the lamp design moved more aggressively to prefer lamp efficacy, maintaining the mean lumen output of the new lamp to be the same as the "original" F40T12, so the design wattage was reduced to 32W. In order to reduce the electrode and ballast (with the higher OCV required for T8 anyway) losses, the current was reduced to 0.27A. That boosted the arc voltage, but since the ballast should have higher OCV anyway, it was of no problem.
In Europe the "evolution" took other approach:
As vast majority of used ballasts were simple series chokes with glowbottle starter, the voltage available for ignition was already high enough. So the tubes were designed to operate on the same ballast. As the current should not be allowed to rise more then few percents and the arc voltage reduced too much, so electrode losses would wipe out the efficacy benefit from the krypton fill, the lamp power was reduced only slightly to 36W (with the same nominal current). Consequence was a lamp of higher output then original, with about the same system input wattage.
But as missing lamp is not a problem for the series choke ballast (unlike on e.g. US HPF RS ballasts, whose continue to dissipate), the extra lumen output was expected to be reduced by not installing some portion of lamps (e.g. use only 3 lamps in a 4-lamp fixture) into the existing systems, so saving the energy use in that way.
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