The LED has come along way! Now you can simply unscrew your standard 320W or 400W metal halide lamp and screw in the Lunera SN-V-E39-400W-320W-5000-G2 lamp (https://bit.ly/2I57zzU) and have instant on LED light with a 60-80% reduction in energy cost. No rewiring!
Watch Doug Root with https://www.AtlantaLightBulbs.com make the swap out.
