Hmmmm.
I think it's probably tough to make a great comparison on that.
But, let's just look at the numbers anyway.
If the Max Consumption is 1500W and the Output is 1000W, then the efficiency = 1000/1500 = 66.7%.
Now, a class AB amp has a MAX theoretical efficiency of about 75%.
So, here's the real answer: A quick and dirty look at the numbers suggests that this amp is pretty efficient for a class AB design.
Why are you worried about how effecient it is? If efficiency is your concern, then class D is far superior to A or AB.