I had a hot bath one evening and decided not to let all the heat go to waste. So I left the plug in until the water had given up all of its heat to the house. But when is the best time to pull the plug out? Should I wait until the water is the same temperature as the ambient indoors air, or should I keep the extra thermal mass in the bathtub, and then pull the plug when the temperature outside the house is at its lowest?
Matt Rutter, Reading, Berkshire, UK
