LED Lighting is flexible. For 2 ft x 2 ft replacement, there are a few approaches to replace the 2 ft linear fluorescent. For any replacement, it is important to consider the luminaire as a system. The fluorescent tube has 360 degree with different types of ballast. 30% of the light is reflected backward and lost.
The old fluorescent troffer uses magnetic or electronic ballasts. The combined cost of fluorescent tube plus the electronic ballast is more expensive than the integrated LED tube with internal driver. The magnetic ballast is cheap; however, it has very low power factor. The electronic ballast is more efficient but more expensive.
Regardless, the proper benchmark should consider all component costs. The direct T8 tube replacement is the simplest. New flat panel is getting popular with about 100 lm/W as the flat panel is edge lit.
A new design using indirect lighting approach could achieve 130 lm/W delivering the same lux as 43 W tubes with only 28 W.
The indirect lighting approach has a complete different polar diagram (see figure 3). It is wider, create less shadow on the ceiling; thus, emulating the natural lighting ambiance.
Lunar Series with indirect LED lighting is more efficient, less glare, wider beam resulting in less shadows an better natural lighting ambiance.