This research aims at identifying the potential of combined solar systems - grid-connected photovoltaic (PV) and solar thermal to contribute covering day-time peak demands in south-east Queensland (Qld). It is generally accepted that electricity demand during the diurnal peak demand period, must be satisfied at a particularly elevated energy cost fluctuating from $2/MWh to as much as $200/MWh for short periods. Author’s previous work shows a close viability of solar energy to contribute covering high demands in Qld, Figure 1. Given the high demand in SE Queensland for air-conditioning and industrial activities, such an approach is considered not only viable, but also economical. Besides covering demand peaks, the solar system – being located on site – offers the advantage of avoiding transmission losses and voltage drops throughout the network. Life-time cost calculations for solar kWh indicate the ability of the solar system to provide competitive prices to cover demand peaks. The project incorporates a 1kW (peak-power) grid-connected photovoltaic and a 1.37m2 (collector area) -120Litre (storage tank) Evacuated tube SWH unit at the University of Southern Queensland. The unit represents an initial technical and economic assessment of the technology at local conditions. Additionally, the project incorporates demand-side monitoring of conditions at electricity distribution substations. A threshold is identified as viable peak load to be supplied by spreading solar units at user sites. The results quantify the power able to be waived by using solar systems in SE Qld. Seasonal demand variations and variations in solar availability are analysed and discussed.