Greg’s lighting allows for a much broader light source for Minecraft. When you have an area needing a significant amount of light but torches and glowstone won’t cut it, Greg’s lighting is here to step in with floodlights.
There are two floodlights added with this mod. One runs on a new type of fuel source: calcium carbide. You make that by combining charcoal with bonemeal. Add that with a water source and the carbide floodlight is now functional. You will still need a redstone source or lever to power the light but this is a relatively cheap method for an exceptional amount of light.
The other more expensive floodlight is made with many blocks of glowstone but it requires no additional fuel outside of redstone/lever. If you have the spare glowstone or if you work mainly in creative mode then this light is a great way to save on how many points of light you’ll need per square block.