As I understand, EchosTAR-11, built by Space systems Loral, was the first 20KW Commercial satellite.
(Reference: Recent Successful satellite systems- Visions for future by D.K.Sachdev).
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$\begingroup$ possibly helpful (or not): ViaSat's 18 kW solar array - largest ever for a commercial telecom satellite? and possibly What kind of power is referred to in “the…most powerful all-electric propulsion communications satellite ever produced” $\endgroup$ – uhoh Apr 24 '20 at 9:10
