There has been a 'fixed escalation' of 15% since the Q1 2011, but the 'variable surcharge' has increased from 13% in Q1, to 18% in Q2 and to 21% in Q3.
So, my understanding is that DEWA have increased their charges by 28% for Q1, 33% for Q2 and 36% for Q4.
Roll on Q4 and beyond ...