You can make your own hot water using only the power of the sun. You'll start with a flat box that's about 3 feet (90 centimeters) square and 2 or 3 inches (5 or 7.5 centimeters) deep. Paint the inside black or line it with black paper.
Next, take 20 feet (6 meters) or more of flexible black tubing. Make two holes in the sides of the box, one near a corner and the other near the opposite corner. Insert the end of the tube through one hole. Shape the tubing into flat loops that don't overlap but run up and down the bottom of the box. Keep looping until you've used up most of the length. Pass the end out through the other hole.
Place a glass cover on the box. Tape the edges to hold it down. You now have a solar collector like the ones you might sometimes see on rooftops. Put the box in the sun. Immerse one end of the tubing in a bucket of water. Suck on the other end to fill the tube and start a siphon action. Keep the end you sucked on lower than the other and let the water trickle into another container. Use a clothespin to crimp the tube and limit the flow to a trickle.
Place a thermometer in each container of water to track the temperature change. Does the angle of the box toward the sun make a difference? What if you use a longer piece of tubing and make more loops? The warmer the water coming out, the more heat it's absorbing from the sun. If you were using water heated this way in your home, you would take the load off your electric, gas or oil water heater, saving energy. [source: Benrey]