Louie is spot on, both with the original comments and subsequent real world measurements.
The original post by Chuck has factual errors and should be corrected or removed.
Pixels are not low power just because they are low voltage.
Low voltage should not be equated to Low power
Interestingly lets look at a one for one with Incans
20,000 incans = 200 strings @.3A-120v = 60A @ 120V = 7200W
20,000 Pixels, set to white, each pixel uses 60mA @ 5v = 1200A @ 5v = 6000W
As Louie has already shown Pixels never draw anything close to the theoretical current and typically are half of it so the 6000W becomes 3000W in real life.
Now lets take LED strings as used in the USA (to be fair to Chuck)
Believe a 70 count string is 2 sections at 120V so 40ma nominal draw.
20000 lights would be 285 strings = 11.4A @ 120v = 1368W
So one for one again normal 120v led strings are more efficient
Now take the LED strings, multiple for 3 to get at least 3 basic colours and we have 60,000 leds to cover 20,000 pixels in colour ability for guess what... the same current draw.
Want more colours... Pixels win the Power game.