If you're in a situation where you need to provide supplemental light, there are several well-established lighting options that are designed to support plant growth. LED lights have some significant advantages over most of the older systems. In particular, full-spectrum LED lights don't require expensive specialized setups like metal halides and some flourescents do. LEDs are available in many shapes, sizes, and intensities and require less energy to operate. They're cheaper to replace, and they don't produce the intense heat of alternatives like HPS.
The grow-light industry changes over time, and old favorites are often replaced by new technology. In this case, newer LED technology represents a significant improvement - high quality LED lights can produce the same amount of light as HPS systems while consuming substantially less energy. They take up less space than alternative systems, which in turn maximizes grow space, and their long lifespan means much less time spent replacing expensive bulbs.