More than 1 petaelectronvolt!!! 1 PeV!!!! If you don't know what are we talking about, there are some energy scales in the wikipedia.
So, the energy of one of these particles detected is the equivalent to a 1 megaton nuclear bomb explosion or also all the electricity consumption of the country of Greenland in one year... All that in only one tiny particle that is almost massless!!!
Of course, if you really checked that page, like my friend Edu, you will notice that I exaggerated "just a little bit" :D That page is in Joules, not eV :) Then, if you multiply per 10^-19 then you get the correct figures. So, we better don't start hypothesizing yet about how we could use these to produce electricity :D Or weapons to conquer the world and all that :P That particle, without almost any mass at all, with a petaelectronvolt of energy had only the energy of around 1000 mosquitoes splashing against your car windshield at a time! I wonder if they would break it...
And remember that our beloved LHC hadron collider at CERN reached so far "only" the energy of 8 TeV!! That is the highest energy ever achieved by mankind when producing particles, and these guys just detected from the sky have around thousand times more! You can think of all that people that was scared about the CERN creating black holes and destroying the world, creating particles of "only" a maximum of few TeV... while we are getting from the sky particles of petaelectronvolts!!!! It's like people scared of the danger for our eyes having too much light if we light a little candle, while they are outside at the sun :D
Ok, it's still much less than the famous Oh-My-God particle (yes, that exists, I did not make up that name!!! :D) which had almost a zettaelectronvolt of energy :D That is about equivalent to a 142 g baseball traveling at about 100 kilometers per hour! (not the world energy consumption, if you also misread the wikipedia table as I did :D ). But it is just a little elementary particle! And scientists don't know yet what created such kind of super-energetic particles, although there are, of course, hypothesis... Science is way cool.