Much cheaper 12v power supply?

[BrianG]

I don't think total mains isolation is needed, but that's my opinion. The protection circuit to ensure full 120v doesn't get to the output should be fairly simple - the crowbar thing was just a quick-n-dirty solution for now.

Triacs are simply gated diodes that are placed back to back so that they pass AC. The only losses are from the small voltage drop. Even at 0.7v and say, 15A, that's still only 5% efficiency loss. But, there would be a little more losses since I'd probably have the rail set to around 15v or 16v, and then go to a linear regulator to provide the steady 14.5v DC. I'll probably pick up a beefy dimmer and play with it a little to see what I can come up with...