Quote:
Originally Posted by TheProfessor
.... is the neighbor saving any money?
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I presume from the description that your neighbor replaced a central tank type heater with a central tankless heater. If that is the case, having a circulator on the system is not typical. It wouldn’t surprise me if the tank system had a circulator, and they discovered that it took a long time to get hot water, after they installed the tankless system.
Assuming the same fuel source, the amount of energy lost through water usage is identical in either system. (The amount of hot water that goes down the drain)
With a tank system, there is further energy loss through the walls of the tank. (The energy needed to keep the water in the tank warm 24/7)
Without a circulator system, you also lose energy from the the hot water that got left in the pipe, after the water is turned off. With a circulator, there is continual energy loss through the walls of the pipe, plus the energy loss attributable to running the circulator.
The savings from a tankless system are largely attributable to avoiding the energy loss through the walls of the tank. If you add a circulator to the tankless system, the tankless system needs to operate often enough to offset the energy loss through the walls of the pipe, which is the same energy loss that would be lost through the pipes of a tank system with a circulator. The tankless sytem would not operate continuously, but would turn on each time that the water in the circulation system fell below the temperature setpoint.
Long story short, your neighbor might be saving “some” energy, but the savings would be nearly impossible to calculate, given the number of variables. My gut instinct is that the savings are probably negligible.
The chili pepper system described above is different, in that it only serves a fixture or two. It is electrically operated, and only produces a small amount of hot water. It would not be intended to replace a whole house tank hot water heater.