Why would they need less power consumption. The lumens per watt of most HID lamps is the same or better than LEDs. This Wikipedia page has several examples of the efficiency of different kinds of lights. Most of the LED examples they give show around 50-100 lumens per watt. For metal halide, they show 65-115 l/w, for high pressure sodium it's 85-150 l/w and for low pressure sodium it's 100-200 l/w. It sounds to me like the HID lamps are MORE efficient than the LEDs, so why is it obvious that the LEDs would use "much less power consumption"?
I'm not pretending to be an expert on the issue, as stated this is second hand information - however, that Wikipedia page seems to describe the kind of lights one would use in general lighting. The lights she's shown me are nothing of the kind, mostly a mixture of red(ish) and blue(ish) LEDs. Apparently that's what plants crave (I suppose the light has electrolytes).