Some devices will divert water back into the system instead of wasting it down a drain! If you like the idea of water returning to your heater, instead of going down the drain, then consider a recirculation pump if the wait for hot water at any one fixture is longer than 2 minutes. If the fixture you are running flows 2.2 GPM for 2 minutes, that is a water waste of 4.4 gallons of water waiting on the water to get hot.
By installing a recirculation pump at the furthest fixture (from the heater), you are creating a loop within your hot water system. This loop draws hot water from the tank to the furthest fixture, then places that hot water back into the hot water supply loop to be looped to the next fixture in the run. All water is retained within a close loop, and none is allowed down a waste drain. There are a number of accessories to suit your specific recirculation needs, ranging from timers to key-ring remote controls, thermostats to remote on/off buttons in different locations through-out the house.

Tankless Water heaters are another way to decrease energy usage. Since there is no tank of water to heat, you are only heating the amount of water that you need. With these heaters, the water is not stored and continually heated and cooled by a thermastat until you are ready to use it. On average, over 40% of your energy spending is in heating water. Even if the shower or faucet isn't running, the heater tank may be heating!!! A tankless water heater saves more than operating cost of energy, it also takes less material to manufacturer (no steel/metal/glass tank), and are considerably smaller than conventional units, saving valuable square footage in your storage/living space. Tankless Water heaters are typically a "Whole House" solution, where "Point of Use" appliances are usually limited to one fixture.

The sister solution for the tankless heating idea, is the "point of use" heating solution.

Most Point-Of-Use water heating solutions can be mounted in the cabinet base of the lavatory or sink it is servicing.

There is a number of different solar powered options for water heating. There is a "Passive" heating solution, and an "Active" heating solution. The Active solution uses a tank to store and regulate the heated water. A thermastat controls a recirculation pump, that will turn on when the water in the tank falls under a preset temperature. The water then pumps through the solar element, were it is heated. The passive solution is a solar panel that loops the water through and heats the water as it is being used. No water is stored and any water flowing is heated and the time of use. This application is good for small public restrooms, and small residences. Another good application is a vacation home or cabin, where the continous heating of water that is not being used would be wasteful.

When designing your next construction project, design green. This is the perfect chance to use resources more efficiently, while creating a healthier and more energy efficient structure. Something more to consider is the impact of the products that you are going to use. Ask questions like, Where is this made? How does the material get to me? How much energy is used in the moving of the material? How much energy is used in the manufacturing of the material? What is the usable lifetime of this material? All of these factors should be considered when designing a green project.