Taking a shower is a modern comfort most of us cannot imagine living without. However, using the shower is the second most energy-consuming process in an average household, number one being heating and cooling (for those with the luxury of AC in their homes).

Taking colder and shorter showers would be a good advice if one wanted to reduce their shower CO2 emission, however, both suggestions go at the cost of comfort. This inspired Dutch Solar Systems to build a heat exchanger which pre-heats your water.

The beauty of the system lies in its simplicity. Almost all of the energy we use for heating water is flushed down the drain. The heat exchanger saves up to 60% energy by recycling the energy to heat water. It lets the (warm) waste water flow away through the same pipe the clean (cold) water comes from, in opposite direction: thus making the warm waste-water preheat the clean water.

Because the system is quite simple the costs are relatively low: around 360 euro. Depending on how often you use the shower in your household, it's fair to say you could earn the investment back in a couple of years. The idea of heat exchange is already being used on an incredibly large scale in the industry, in many processes from making paint to refining oil. It would be great to see more of these efficiency increasing ideas go into our households.

This system is a nice example of how simple and innovative ideas could increase efficiency in households. With this system you could reduce your CO2 emmision when taking a shower while saving money at the same time and without giving up giving up any comfort.