There are several options to choose from when deciding on the best indoor grow lights. You want to look for the best of both worlds, you need a light that is inexpensive to run but produces the most results. For most experts this means using a few different lights for different jobs.
High Intensity Discharge Lights
These lights are found all over the place in the world. They are used in street lights and stadiums for example. High intensity discharge or HID lights work by creating an arc between electrodes housed in a transparent arc tube. They have metal salts and gas in them that produce plasma which is very bright and intense.
High Pressure Sodium
High pressure sodium lights or HPS lights for short are an example of an HID light. These lights use sodium in an accelerated state to produce the light you see. There is also a version of these lights known as low pressure sodium which are much more efficient, however the light they emit is very limited and is not good for growing.
HPS lights emit a very broad spectrum and can be used for vegging and budding marijuana plants. Most experts do not use HPS lights for vegging because they are not very efficient compared to other options. For budding however HPS lights are the clear choice for experts. They emit the perfect spectrum of light.
HPS lights require a lot of air and ventilation because they can get very hot. They can heat a small grow room very quickly to the point of actually overheating plants if there is not proper ventilation. HPS lamps are also relatively expensive but given these few setbacks most experts would tell you HPS lights are the way to go for flowering.
Fluorescent lights are the common lights you probably use in your house. They are cheap and easy to maintain. They do not need much ventilation to stay cool and they can be purchased at any hardware or home store. They also just happen to emit the proper spectrum of light to be great at vegging marijuana plants.
This is why most growers will have vegging plants under several fluorescent lights and the budding plants in another room under HPS lights. You can use as many fluorescent lights as you can get into your room and even set up fluorescent lights on the sides of plants to encourage plants to grow out and not just up.