--- Well...
As I recall, If you take a look at a Zener data sheet you'll find that the peak power it can handle (the Zener, not the data sheet ;) increases as the width of the input pulse decreases.
For example, if the input pulse lasts for only a half second, a 10 watt pulse will heat the Zener up as much as 5 watts, continuous, will.
If I recall correctly, TVS diodes have their dissipation rating based on a 3 millisecond pulse, so a TVS diode rated at 1500 watts would really be dissipating only 4.5 watts
--- Yes, I know.
I stated that earlier but made the error that they're not called bipolar, they're called bidirectional.
--- JF