There are a number of great features that LED Grow Lights have over conventional High Pressure Sodium (HPS) and Metal Halide (MH) lights. Let's take a quick look at the most impressionable differences.

1. LED grow lights are more energy efficient. They use 75% less electricity then MH and HPS lighting systems. Depending on the size of your indoor garden, this could mean significant savings. With standard grow lights (HPS and MH) you are looking at using approximately 25W per square foot of grow area. This translates into about $15/sqft per year. A good size garden is generally about 50sqft which means electricity costs can be as much as $750 per year! With LED grow lights on the other hand, you could be saving as much as $500 or more per year.
2. LED grow lights last longer. With life spans of 50,000 hours on average, they will last 2-3 times longer than your conventional grow lights. There are also no ballasts to replace which also reduces the heat output into your growing area.
   
3. LED grow lights produce less heat. Most of the electrical energy that is being used is converted into light, as opposed to MH and HPS lights. LED lights average temperature is typically around 100F where as the HPS and MH lights can get as hot as 750F.
4. LED grow lights have a customizable light spectrum. Depending on whether you are looking for proper lighting through vegetation or flowering stages of your plants, LED lights can have a number of different spectrum's. General lighting conditions can be used which have sufficient red and blue areas if you are not too picky about ideal lighting conditions. Conventional grow lights have a lot of the output in the yellow and green spectrum which is nearly unusable to the plant during photosynthesis. LED lights on the other hand can use a specific spectrum to maximize usable light to the plant.
   

LED grow lights are a bit more expensive. If you use grow lights, the return on investment is probable less than a year. There may be additional savings in reduction of air conditioning costs due to less heat being produced as well.

Many places online are beginning to sell them. Some care should be taking to find the correct wattage of LED light for your particular garden. As stated above, less energy is required and thus the wattage per square foot is greatly reduced. Many of the sites that sell LED lights have calculators to determine what you would require.

Good luck on your indoor gardens!