Many of the older homes in the United States would benefit more (dollar for dollar) from simply re-insulating the windows, attic, and outer walls than they would from installing Solar or Wind generators.
Better insulation on your home will tremendously lower your energy bills, but it doesn't stop there. There are many things you can do to help lower the monthly bills even further.
One easy option is to ask your power company to perform an energy efficiency audit on your home. For little or no cost, they can pinpoint insulation problems, window leaks, inefficient appliances you may have, and some will give you free CFL or LED light bulbs to replace your incandescent bulbs in your home.
If your power company is anything like ours (Alliant Energy) the auditor may also make quick fixes such as caulking a leaky window or weather stripping a doorway for free.
These auditors are also experts at helping you get every rebate imaginable when it comes to making your home more energy efficient. They can help you find rebates for everything from the CFL light bulbs all the way up to Insulation and appliance replacements. You'll be surprised how many rebates there are for decreasing your home's electrical and gas needs.
Becoming more energy-aware will also help lower your energy needs. Shutting off appliances and lights when not in use, keeping your thermostat one or two degrees away from your normal comfort level, lowering your water heater by a few degrees, ect. are all ways to increase energy awareness and lower your bills.
Once you've accomplished making your home as energy efficient as possible, if you still are not satisfied, then you should consider solar or wind energy.