I have a 20 by 30 garage that I use as a shop. Its has a finished ceiling at about 9 ft. 22 years ago I installed 9 used T12 four bulb commercial troffers flush in the ceiling. Lots of light, no issue there. I've since installed an air conditioner for the summer months here in Arizona. The AC is a 22 SEER mini split. The AC does fine in cooling the shop down but when I turn on the lights, tools, and dust collector it can't keep up. Might lights draw 14 amps at 120V. The AC is rated at 24,200 BTU. I assume that essentially all of the energy the the lights draw is converted to heat. Some in the ballast, the rest in the bulbs and then the light hits surfaces and heats them. The lights are drawing around 1600 watts which is 5500 BTUs. I would like to reduce the heat the lights introduce into the shop.
I would like to replace nine the old T12 four bulb 2 ft by 4 ft troffers with new high efficiency T8 two bulb troffers. Price isn't a super concern. This would reduce the number of bulbs by 1/2 and the new ballasts will be much more efficient. The holes are already in the ceiling for the existing troffers so I will be using the same locations.
Questions;
1) Will 18 four foot bulbs be too little light, should I chose three bulb fixtures?
2) What brand troffer should I buy?
3) What brand of bulbs, or does the efficiency change much?