The 180 watt ( 135 watt actual ) then I'm a good guy and I give a 40% efficiency so you have 54W real watt, the rest is just heat.
Sun power is around 50w square ft top
Actually, LEDs are very efficient, more on the order of 80%+. A MH or HPS would be more inline with the 40% as they put out massive amounts of heat. LEDs in any light are driven to about 65-70% of there max as this is the point where they produce the most light with the least heat. Driving them to 90% + only gets you maybe a 10% increase in output, but doubles the heat, and also shortens their life.