The off-grid PV-battery powered home revisited; the effects of high efficiency air-conditioning and load shifting

Abstract The potential for residential households to go ‘off-grid’ with a photovoltaic-battery storage system in a location where a conventional connection to the electricity network is available has received recent attention. Several studies have reported that at present, in Australia the economics are not justified. These studies have used unmodified electricity consumption profiles from grid-connected households as input to their off-grid system analyses. However, households looking to go off-grid may be motivated to make basic modifications to their consumption pattern so as to minimise the size of the PV-battery system. Here the effects of (i) shifting the booster time of electric storage hot water system to coincide with peak irradiance, (ii) improving the efficiency of air-conditioning appliances, and (iii) shifting pool pump operation and improving pump efficiency are compared and assessed. The analysis uses sub-circuit measurements of electricity consumption from 28 households for up to 2 years. Results show that the hot water and air-conditioning adjustments in particular can improve the economics considerably, even accounting for the fact that the appliance efficiency improvements also lower the grid connected electricity costs. For households seeking to go off-grid, any changes to electricity load profiles that provide a more uniform match of consumption to generation in particular, improve off-grid system economics in comparison to grid electricity, since the true cost of delivering electricity from the grid at peak times is typically spread across all consumers.