The graph is absolutely meaningless to me without further contex. So, the electric grid generates 12.7 "units". If we subtract solar, wind and hydro then we get down to 6.42 "units". I have chosen these because they are not thermal power sources. These power sources generate an almost equivalent amount of primary energy and electricity. So we are left with 6.42. 6.42/31 is 20%. Where are these 20% efficient power plants? Nuclear alone would be 30% efficient. Combined cycle gas is 50%. The numbers make no sense to me.

Edit: Ok I read the note at the bottom and the graph literally adjusts the rejected energy of renewables to match thermal power plants. Assuming 33% efficiency that means 12.56 phantom units of energy that never even existed in the first place are being rejected.