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Posted by HeatPro on July 07, 2007 at 08:20:29:
In Reply to: Re: Ergomax or equivalant posted by Dee on July 07, 2007 at 06:53:25:
": 55 degree water heated to 125 degrees must surely cost less than 55 degree water heated to 180 degrees and then cooled back down to 125 degrees with the addition of more 55 degree water."
You reworded the point of contention better this way. It can be answered with less "lecture":
A. It costs what it costs to heat the water to whatever. It does cost more to heat water to make it hotter, as more energy is invested (the measurement being btuh in that instance.) The difference in cost is due to using more fuel to do so. Also there is the penalty of the heater emitting more btuh energy from a hotter boiler while it is hotter. That is the basis of the AFUE boiler testing (it isn't a large loss from a boiler any more as they come from the factory with better than 84% AFUE today. Thus a steam boiler is a bigger waste of energy than a hot water boiler, as a steam boiler hits 212F or better every time heat is called for.
B. After you heat the water and make use of it right away, whether it is mixed with cold water or not, the heat energy in the water is used for its purpose, so there is no loss.
C. If you store the water for some time after heating it, whether mixed with cool water or not in the tank, there is additional loss from the tank (limited by its insulation) and the attached piping.
The point of the coffee story is that few would think there is hot water lost nor much heat lost from the sides of the coffee cup when more water is added to the cup (unless the cup spills over and it is lost instead of drinking the coffee.)