Although the solar hot water panels have improved in efficiency over the last 20 years, the problem still remains that a booster is required for the winter months where the clouds obscure the sun. The boosters are simple heating elements typically consuming 2.4kw of electricity for each hour the booster is running. A completely cold 300L rooftop tank will consume over 14kw/hr of electricity to heat the tank to 60 degrees. The second problem is that the improvements in efficiency mean that unless there are 4+ people in the home that the tanks can heat to 99 degrees in summer and have no option but to mechanically dump the hot water to protect the tank from over pressure. The third issue still remains that the solar hot water system is consuming valuable roof space typically on the north aspect of the roof where PV electrical solar panels could be positioned to maximize generation.
Finally with maximum electrical draw from a 270L is just over 1kw/hr with a typical full heat requiring 4kw/h, the iStore has built-in timers which further allows consumers to take advantage of daytime PV solar generation to save even more on running costs.