I installed a Sanden Heat Pump hot water unit purchased from Sackett Services last year in early November. I have attached to the circuit a wattage meter to monitor the power consumed by the system. I can happily report that the system is running on 1/4 of the power the old mains pressure hot water cylinder it replaced. The old system consumed 100 kilo watts per week, while the Sanden consistently runs at 24 kilo watts per week, exactly as promised in the brochure. I have also been impressed how quiet the heat pump runs.
Thanks Mick for the support and recommending the Sanden, I am most impressed.