Bob,

An interesting idea.  Be sure to find out what the efficiency of the power supply is across its operating range, both input voltage range and output current range.  When a product claims to be 95% efficient that's usually its best efficiency at a particular load and input voltage.  I've seen supplies that are over 90% efficient at 85% load that drop off to less than 40% efficient at 30% load.

Tom Gourley