It is pretty common in the homebrewing craft to have a chest freezer with a temp controller. You use it to control the temperature of fermentation or the serving temperature. A cheap chest freezer and one of these controllers makes a high efficiency refrigerator that is also much cheaper to buy:
NORTHERN BREWER: Fermentation Temperature Control
I have the Johnson Controls A419 and a $100 chest freezer from Lowes, it is very dependable. I haven't run it on a KillaWatt so I don't know how much load it draws, but I doubt it is very much.
Here is a heat pump design that uses water stored in an insulated attic space to store heat. The heat is generated either by solar energy into the water and then vented into the living area, or if the stored heat is not warm enough, by a heat pump (air conditioner with the hot end pointed into the living area and the cold end pointed into the attic.
Thermal Attic - Solar Heating & Natural Cooling Systems
The designer frequents the "small houses" group on yahoo. There are some very well thought out design discussions there. If you are not already in the group, they would love to hear about your experiments.