The ironic thing about bodily hygiene is that room temperature water is as good at killing bacteria as warm or hot water, incidentally its effect is negligible.

The ironic thing about bodily hygiene is that room temperature water is as good at killing bacteria as warm or hot water, incidentally its effect is negligible. Soap works better in warmer water, however as more and more people use liquid soaps and hand washes its meaningless as the added surfactants enable it to work just as well at lower temperatures. In fact many liquid soaps are better at removing grease and dirt at lower temperatures than standard soap is at better temperatures. Then there's the whole problem that frequently washing your hands in warm water without a good liquid soap (which typically contain antibacterial agents too) can actually increase the bacteria on your hands due to the added moisture and temperature. Dropping the temperature of your shower to room temperature will not only save you significant amounts of energy but will wash you just as well. In fact plumbing a cold water storage tank into your shower line and keeping it in a well insulated area of your house, you can spend virtually nothing on heating your shower water. Even adding a cold water storage tank to your shower line will likely cut the energy usage of your shower in half even if you take a hot shower. Most showers either run off a hot water tank (majorly inefficient) or an on-demand hot water system (either one that replaces the hot water tank, or a stand alone shower unit connected to your cold water line) and both ways end up heating ground temperature water: water lines stay at ~55F, room temp is between 68F-77F and a hot shower is 85F. So even if you like a hot shower, simply adding a holding tank to the cold water intake of your shower can reduce the amount of energy you use phenomenally (potentially a 2/3 reduction). If you're in and out of a shower in 5 minutes, you likely only need a 25 gal tank, but for an average household I'd recommend perhaps a 100 gal tank, just in case.