Energy production in Greece is dominated by the Public Power Corporation (known mostly by its acronym ΔΕΗ, or in English DEI). In 2009 DEI supplied for 85.6% of all energy demand in Greece, while the number fell to 77.3% in 2010. Almost half (48%) of DEI's power output is generated using lignite, a drop from the 51.6% in 2009. Another 12% comes from Hydroelectric power plants and another 20% from natural gas. Between 2009 and 2010, independent companies' energy production increased by 56%, from 2,709 Gigawatt hour in 2009 to 4,232 GWh in 2010.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): How much of all of Greece's energy demand was supplied by DEI in 2009?
85.6%