Washing Hands in Cold Water

It takes a while for the shower and faucet in our upstairs bathroom to run warm. I lost my taste for cold showers in wartime Britain, so we just run the shower until the water is tepid. (Is there a difference between "tepid" and "lukewarm" in the context of running water?) Water, it is said, is the new gold, and we do what we can to conserve it. For some time now I have simply washed my hands in cold water. I readily admit that when I am washing downstairs, I use the hot water faucet. Especially if Barbara or a guest has just washed their hands, I like it when warmer water begins to arrive, but I don't waste a drop of water. But we pay for our water, and though I remain smug about being a good citizen, I do wonder if at least part of my motivation is the knowledge that I am saving money, as well as water...