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=====  Fluorescent fixtures T12 to T8 =====


I've retrofitted most of my older fluorescents with electronic ballasts and T8 lamps. To my eyes, the light output appears to be about the same or a bit higher.

This may be partly because I'm comparing new lamps to old ones. Initial lumens of a typical F40T12 "cool white" T12 lamp is around 3000. Initial lumens for a F32T8 4100K T8 lamp is around 2950. So, in theory, a tiny bit dimmer - but T8s maintain their output better over their lives, so a 5 year old T8 will be brighter than a 5 year old T12.

Note that this is the output using ballasts with normal ballast factor. Most standard ballasts slightly underdrive T8 lamps, to about 90% of their rated power (and light output). This is where some of the advertised energy savings comes from (though they really are more efficient at turning electricity into light).

If you want a dramatic increase in light when you fit new ballasts and lamps, specify high ballast factor. This runs the lamps at typically 108-115% of rated power, or around 34-37 watts, and increases output to 3200-3350 lumens.

High ballast factor ballasts can be tough to find, but in most cases you can accomplish almost exactly the same effect by fitting 2-lamp fixtures with 3-lamp NBF ballasts and capping the third output wire.

Your Lithonia fixtures will probably come with NBF ballasts unless you order them otherwise (they'll probably be Advance REL-2P32-SC). You'll lose a few lumens to the diffuser. The new lamps should more than make up for that loss. So, I'd guess that your new light level should be a bit higher than your old T12s.

Assuming you use 4100K lamps, the new ones will also seem brighter, lumen output aside, because of their higher CRI. Old T12 cool white lamps have a CRI around 63; new T8 4100K lamps are usually 78 or 82 CRI. This makes colors look brighter and truer, and whites look less dingy.