Kill-A-Watts tell what the light is drawing in total. This does not account for losses in AC-DC conversion and fans, which isn't a whole lot. Power draw from the wall determines operating power of the LEDs. When they advertise their light is 300W, but only driven at half power, its actually 150W.
LED types/brands do matter also since cheap Chinese LEDs will take more power to emit the same light as Cree and other high quality emitters that will output the same amount of light with less power. For instance, the new Cree XTE royal blue LED is forging the new standard of higher efficiency due to its lower Vf and more output power at the same current at the XPE. It also has a more uniform light distribution over the viewing angle. I hope they have other colors coming in the XTE series. I'm waiting to build more for this series to expand.
I wouldn't use a commercial lamp other than ones proven to use top emitters and rate their power draw appropriately. Most just rate the light on LED maximum power, not actual driven power to trick unknowing consumers. Too bad there are a lot of shady people out there trying to make a quick buck rather than a great product.
Great thread, gives people a heads up on who is just trying to make a quick buck vs. making a decent product. Although most won't jump intot he LED world until it can compete with HPS in price. They are becoming more efficient and running cooler, so that is one advantage. I wouldn't expect a commercial lamp to run as cool as a DIY light with top quality emitters though since they load the case with fans, I'm betting there are hot spots on the heat sink due to the tightly packed array on a thin heat sink to save costs.
LED types/brands do matter also since cheap Chinese LEDs will take more power to emit the same light as Cree and other high quality emitters that will output the same amount of light with less power. For instance, the new Cree XTE royal blue LED is forging the new standard of higher efficiency due to its lower Vf and more output power at the same current at the XPE. It also has a more uniform light distribution over the viewing angle. I hope they have other colors coming in the XTE series. I'm waiting to build more for this series to expand.
I wouldn't use a commercial lamp other than ones proven to use top emitters and rate their power draw appropriately. Most just rate the light on LED maximum power, not actual driven power to trick unknowing consumers. Too bad there are a lot of shady people out there trying to make a quick buck rather than a great product.
Great thread, gives people a heads up on who is just trying to make a quick buck vs. making a decent product. Although most won't jump intot he LED world until it can compete with HPS in price. They are becoming more efficient and running cooler, so that is one advantage. I wouldn't expect a commercial lamp to run as cool as a DIY light with top quality emitters though since they load the case with fans, I'm betting there are hot spots on the heat sink due to the tightly packed array on a thin heat sink to save costs.
