LED lights can be made using different sized diode chips from less than 1 watt per diode up to 20 watts or more per diode chip. The ideal chip size for a LED light will depend on the use for the light. As the chip size gets larger, the light is more intense but the diodes give off more heat and require a larger cooling mechanism.
The ideal chip size for most indoor growing applications is the 3 watt diode chip. When LED grow lights first appeared on the market several years ago in 15x15 panels of 225diodes, they used diodes which were 1/16 of a watt per diode. These grow lights were effective in photosynthesis of very simple plants like sprouts but failed to grow larger plants. Larger plants requiring fruiting needed larger diode sizes. The 3 watt diode LED grow light soon became the standard for LED indoor grow light.
Many LED grow light resellers have entered the market and in an effort to differentiate themselves some have turned to the 5 watt and 10 watt diode chips. These larger diodes have shortcomings when it comes to indoor growing. The larger chips give off more heat and require more heat dissipation. They need larger heat sinks and make for a heavier product. The 5 watt and 10 watt diodes also require the grow light to be larger because they can not be manufactured in a dense network like the 3 watt diode chips.
Additionally, the 5 watt & 10 watt chips tend to cause brown spots to be formed on the plant leaves due to the extra intensity of the light. The 3 watt diode chip is the perfect size for an indoor grow light. It can penetrate 5-6 feet past the plant canopy and can be packed in a dense network configuration which is the ideal design for growing fruiting plants. The light from the plant is not overly intense where it can cause leaf spots but is strong enough to provide the energy necessary for full photosynthesis of fruiting plants.