20W(X4)=I(amps) X E(voltage)... Idk what voltage u r using... If u r in the US, u likely have a 110V, 20A circuit to plug into... So, if this is the case, u r only pulling .72 A... So, a cable rated for this would work in as small as 16AWG... But, overkill in circuitry never hurt anything, and...