Plants need light in order to photosynthesize. HPS grow lights are tried, tested and proven as the standard artificial indoor grow light. In general, higher wattage = bigger overall yield,.. but remember though HPS light produce a lot more heat, so ensure you have adequate ventilation to extract the heat. Magnetic light kits are solid and can only turn on or off, whereas digital kits can switch between 250w, 400w, 600w and most have a boost option to 660w.
