We've recently changed to Powershop (from Mercury after looking at Powerswitch) and for the first month pretty much everything worked as I expected. Per unit rates for both properties were in the mid 20-30¢ range which was competitive with Mercury. 

We are retired so we are able to go to the bach for sustained periods, in fact we spend much more time during the summer at the bach than we do at our main residence. Our annual consumption for the past year at the bach was a healthy 7000kwh and over 9000kwh at our main residence. So not low users then (despite my best efforts).

During this first period however we haven't been out to the bach so the power consumption has been (for us) pretty low (about 7kwh per day) so come the first Powershop review the rates for the bach have jumped to 44¢ and more for future periods.

Clearly as soon as we spend some time at the bach the consumption there will go up and we will pay these high rates per unit until we establish a higher demand pattern at which point future rates will drop - just in time for us to leave and experience higher rates at home where demand has been low. 

The Powershop model seems to be based on a stable consumption model i.e. predicting future demand from very recent past history. It seems to me we will have difficulty working with this.

Perhaps if the demand for the two premises were aggregated or the rolling average were for a much longer period it might work or am I missing something?