I am always amazed, here in the Southwest, how few homes are built with basements. We have no problem with water tables and the excavation is fairly easy in most areas. There are obvious huge energy advantages to having portions of your home underground in extreme climates. The main answer I've gotten from builders is that, because land was so cheap out here, it was so much easier and less costly to simply sprawl out on the surface than to consider the basements.

New basement building techniques have made construction simple these days. Interlocking styrofoam blocks are now available that, when filled with concrete, are stronger, more energy efficient, and less expensive than the old techniques of using concrete forms or block construction.

You mentioned air conditioners. I recently saw a show talking about a new efficient design for a heat pump system that, instead of using a condensor unit that transferred heat to the air, a ground loop fluid system was used. A large pit is dug outside the residence where a long loop of tubing is buried deep enough to where temperatures were fairly moderate. A fluid such as ammonia was then circulated in that loop to transfer the AC's heat into the ground. The efficiencies of those units, not to mention the lack of need for noisy condensor fans, were about double that of traditional systems. It also enabled these heat pumps to be used for heating houses in extremely cold areas.

Imagine the energy impact if there were true incentives for us all to use these types of technologies.