Pre-cooling works best when your house has a lot of mass built into it, also known as heavy construction. In a heavy house, pre-cooling tile-over-slab floors, masonry fireplaces, granite counter tops, masonry perimeter walls etc. allows the house to store a lot of the pre-cooling energy and coast well into the on-peak period without requiring additional air conditioning. Light house construction (frame construction, carpeted floors, laminate countertops, drapes etc.), on the other hand, will not have enough mass to store much of the pre-cooling energy.
Any pre-cooling strategy has to be operated long enough to cool the structure and not just the air. If your house is heavy, I’d recommend pre-cooling it down eight to 10 degrees for a good four to six hours prior to the on-peak period. If your house is light then a four- to six-degree pre-cool for a couple of hours should be fine.