WOW :o that ain't cheap!

BTW: Watts = Volts * Amps

2/3HP: 110V * 9A = 990W
1HP: 220V * 7A = 1540W

The 1HP will most likely run less, but your overall operating cost will likely be the same. The same amount of energy is required to pull the energy (Heat) out of the water regardless of how fast it is removed.

The 1HP will definately have a lower duty cycle, so it will last longer and provide the savings in the long run.

... Nice piece of equipment!