This paper documents the utility of the online tool "rainwater harvesting and demand simulation" forwarded by URL http://gettanked.orgi, and categorizes performance variability with respect to KOppen-Geiger climatic classifications of the Australian continent. This is a novel tool because it dynamically calculates the irrigation and evaporative cooling demands in addition to any particular per diem allocation of potable water. The analysis may be either from a finite storage tank of specified capacity, or drawn from water mains, but the present paper is focused on the design of secure off-grid rainwater harvesting systems (RWHS). The nominal consumption target of 155 L per diem per capita must be reduced by varying degrees depending on the locality. Higher demand can be met if sufficient catchment and capacity are provided, or if regular tanker deliveries are readily available. Alternatively, demand restrictions are tabulated as guidance to avoid running dry within the constraints of a nominal 10,000 L capacity storage with 100 m2 catchment-defining the sustainable load per diem (SLPD) during a "worst case" epoch-this is the break-point for off-grid security. SLPD varies from 86 to 124 L/d among most temperate maritime climate stations, and between 35 and 42 Lid at most desert climate stations. The supporting on-line operating manual includes tabulations of demand for evaporative cooling and irrigation together with the sustainable yield of a rainwater harvest system at 128 locations throughout Australia. Dynamics of non-potable demands should be resolved before using the GetTanked design tool for any particular dwelling or workplace. Indoor and potable water demand must be disaggregated from irrigation, pool evaporation, and evaporative cooling in order to fully exploit the GetTanked tool. (C) 2015 Elsevier B.V. All rights reserved.