You'd be surprised how much heat is lost in the heating pipes and ducts running around your home. Easily, one of the most energy-efficient ways to save on costs is with simple fiberglass duct insulation.
One man's trash is another man's solar water heater! By using household junk, most of which you can get for free at the local landfill, you can make your own thermal water heater for less than the price of a fast food meal.
The next time your friend with a swimming pool is out of town and you desperately need to cool off, try this fun little project for a batteryless, solar powered personal fan.
Taking you back to high school shop class, here's how to make your own wind turbine blades out of wood. The wood base easily picked up at any home building store (or heck, from fallen trees in the nearby forest), wood turbines are a more affordable option for a do-it-yourselfer as you can measure and handle the wood before you purchase and begin cutting.
Windows in your home have been known to let heat seep out, but by building your own Heat Grabber, you can reverse the process! Amazingly, this solar collector can cost you as little as a few dollars per square feet and a couple of hours.