The Australian Government department of Energy Rating tests and issues the Star rating for all products. www.energyrating.gov.au states "Solar, heat pump and electric instantaneous water heaters do not have energy efficiency requirements."
The Federal goverment Clean Energy Regulator(CER) issues certificates that indicate how much energy can be saved in the remaining 8 years of the ERF/ACCU schemes. An iStore can save a household between 24Mw to 25Mw of power(depending on location) in that period and based on these certified results the CER provides incentives to home owners to install this technology.
When compared to electric or gas hot water systems an iStore can easily reduce the energy used by 70%, this figure is certified and used for state based rebates such as those in Victoria and New South Wales.