Geothermal is absolutely the way to go in terms of efficiency- but the cost is high. In Delaware, it is hard to make solar or wind work, but that can vary greatly state-to-state because of the rebates and incentives offered by the state government.
Our link can teach you about some of the things we put into our homes.
800 729-5111 Ext 420
In reguard to geothermal HVAC I am not a huge fan in the smaller homes, when the geothermal guy I work with comes to the build job meeting allmost all he talks about is how to insulate the home not about saving $$$ vs the 95% system he compares his system to an 80% efficency hvac system. The ROI is terrible on goethermal when compared to a 95% , 15 seer or greater unit on a well insulated tight home. Our homes avg 34% more efficient then the 2006 IRC code. Using better equipment. My cost geothermal 18,0000 vs 95% gas 6000. The geothermal does not have good ROI even with the tax credit.
Foam insulation is some of the best $$$ you can spend on new construction with a typical ROI of 4-6 years. Our hybrid system is about 10-12 months. Our cost for standard insulation about 1800, upgrade to the hybrid system 2800, upgrade to foam 5800. ( our hybrid system cost will increase +1200 in july 2011 new e star code )
Solar and wind power not even a consideration on an single home, the future may be communities with a shared grid with large systems were all homeowners benefit.