Building a new house, how to make it efficient?

[Flatland2D]

My wife and I plan to build a house out in a small town in the start of the Texas hill country. I will be building the house myself, but will hire a contractor for the major things like pouring a slab and maybe the framing. What are things that I should include to keep energy bills down? Right now I'm thinking of making the outside walls 6" thick instead of 4" and using a good quality insulation. Cost is an issue so suggestions can't be too expensive, but I'm willing to pay a little more to have things done right. I guess I should look into energy efficient windows and things like that. I haven't been researching all the new home gadgets yet.

Temperature down here can go over 100 in the summer and it stays hot most of the year. The real challenge will be finding an energy efficient cooling system. Winter lasts a month or two, and even then it rarely drops below freezing. We intend on having a wood burning stove for those days and an electric heating system as backup. Also, the floorplan we want to build is almost 3000sqft, but might not build it all at once. We are going to try and stay away from things like lofted ceilings and such.

The house should be pretty neat once it's built though. All the water will be collected from the rain, as that or a well is your only option out there. The location we want to build on is next to a creek, so we'll use that for irrigation. If I could only get the house on renewable energy, it would be completely self-reliant. However, I'm not sold on the idea of solar electricty - too expensive as of now. I might run some outdoor lights and other small things off a solar panel and battery, but that's all I could see happening.