Fig. 5. Comparison of energy consumption for NO production in various plasma reactors. Original references: 1980s low pressure MW plasma,^64,65,77,78 MW plasma,⁶³ gliding arc,^{33,34,53,60,62,79–82} RF plasma,^83,84 DBD,^36,53,85,86 inductively coupled HF,³⁵ spark discharge.^54,55.