ben, I was referring to the energy inputs to manufacture and install the units vs the energy saved during operation. It was only a rough figure, depending on where I looked, figures higher and lower were quoted, 10 years seemed to be about the average. But as you pointed out there are so many variables and other inputs that may have been overlooked. The investment and running costs are a different matter, but it looks to me the money would be better utilised sitting in a low yielding bank account. I think we will know the day that the systems have reached an acceptable level of efficiency, people will be installing them without any rebates.
