References are available to calculate skin effect, RAC/RDC given wire gauge and frequency. But my problem is a complication of this simple calculation. Say I have a 1 Amp RMS AC current component and a selected wire size that gives me a skin effect of 7X the DC resistance. But I also have a hefty 10 Amp DC current component. I'm interested in calculating the total I2R losses due to both the AC and DC currents. How are these two combined?? For the sake or argument, the DC resistance of the wire is 0.01 Ohms. 1) I can treat them as separate and independent currents and get a small power loss: P = 0.01 Ohms * 102 Amps2 + 0.07 Ohms * 12 Amps2 = 1.07 Watts. Or 2) I can imagine that the 7X skin effect also impedes the DC current flow. P = 0.07 Ohms * 102 Amps2 + 0.07 Ohms * 12 Amps2 = 7.07 Watts. The results are wildly different between the two. Which method--or a third method, is correct to first order? I mean, never mind the finer details. I just want to know what my power loss is to +/-20%.