Indoor gardeners are faced with a decision when they consider light sources.  To go with tried and true conventional HID (high intensity discharge) grow lights, or the more costly (initially) LED (light emitting diode) grow lights.  One way to make this decision is by considering costs.  

LED grow lights are more efficient than other types.  Far more efficient, in fact.  Conventional grow lights operate at around a 35% efficiency, while LED grow lights operate at 90% and higher efficiency.  The reason for such a great disparity lies in how they work.  

Conventional grow lights produce pretty much a full spectrum of light, while LEDs can be engineered and designed to produce very specific wavelengths of light.  Plants use red-orange light for food, and blue-violet for reproduction.  Most of the rest of the spectrum is not used.  LED grow lights take advantage of this by converting electricity into only the useful wavelengths of light.  Conventional grow lights, on the other hand, convert electricity into useless wavelengths, and most wasteful of all, heat.  

LEDs produce virtually no heat, at least as far as the plants are concerned.  There is some heat production, but it is limited to the base of the ligh and not radiated out onto the plants.  Conventional grow lights need a separate cooling system as a result of all this heat production; otherwise the plants can be burned.  LED grow lights don’t require a cooling system.  Plants also require more watering under conventional grow lights.  

Extra expenses for conventional grow lights also entail the purchase of items such as ballasts and reflectors.  Again, LED grow lights don’t require these things.  Conventional grow lights scatter light in all directions and so need reflectors to try to cut down on the losses.  These losses are in addition to the already mentioned losses that occur due to the production of wasted light wavelengths and heat.

Then there is the matter of life expectancy.  LED grow lights average from 50,000 to 100,000 hours.  Conventional lights may require replacement as often as every 5,000 hours.  10 to 20 times as often.  Over time, you can see just how expensive this could get.  While you may spend around $150 for a 400 watt HPS grow light, you might need to replace the bulb 10 times before you would need to replace an LED grow light with an equivalent effective wattage that cost around $400 to $500.

It should also be noted that it is important to buy LED grow lights that are at least 1 watt per LED.  Some grow lights are sold with wattages as small as 0.06 watts per LED, but these are to be avoided because they will be ineffective for growing plants.

The advantages of LED grow lights outweigh the initial higher cost, and in the long run, the indoor garden will cost less by using LED grow lights.