Its hard to believe it is the wattage it says, normally it will say the true wattage somewhere in the small print but I cant see it.
So its difficult to say. But I would say its not close to that wattage based on the chips used. That said you wouldn't need that sort of real wattage to light a 5x5 anyhow.
Just beware there are COBs and there are COBs, unfortunately since COBs really made a name in the growing world thanks to folk on here and other forums and youtube everyone jumped on the bandwagon and started knocking out "cob lights" left and right.
The word COB sells, like tits in a lads mag, but it is not the COB that is special, its the efficiency of the light, something like a creecxb3590 , which is kind of where it all started are very efficient, but they are also white light with a great spectrum.
Epistar are not efficient in comparison and they are still using targeted spectrums with reds and blue diodes.
EDIT.. I found the info on the coverage and it says that light will cover 2ft x 1.5ft in bloom, so to answer your question NO. when you take that coverage into account its actually really poor value for money.
EDIT2 somehow I missed the real wattage on the page. It's 680w. Now take that and consider the above statement on coverage and those two things do not add up at all. A 680w light that only covers 2ft x 1.5ft that is really really bad, it also says it has a lumen output of 30000, I know lumens are a poor measure but shit that's terrible, possibly the least efficient light I have ever seen. I mean even a 600w hps puts out 90000 lumens, this light uses more power to create a 3rd.. STAY WELL CLEAR!!
P.S sorry for waffling on, I couldn't be bothered to delete my post and rewrite it...