How to read AC power dissipation in LTSpice components?
If you're referring to what the status bar displays when hovering over an element, or what an .op label might show, those are readings from t=0, the very beginning of the simulation, where the operation point is calculated. Even for DC circuits it may change due to transients in charging capacitors, etc.

LTspice provides a way to display the power dissipated in any element by pressing ALT and then RightClick on it. This will plot the instantaneous value, which can then be further calculated with CTRL+Click on the waveform's title (in the waveform viewer).

Of course, for more math, one can always add external circutry that calculates this automatically. For example, you could make use of this example on how to average the AC power over a cycle, thus displaying a quasi-instantaneous average dissipated power (with a cycle delay).