Investment Feasibility Analysis of Rainwater Use in Residences Enedir Ghisi & Pedro Neves Schondermark Received: 22 November 2012 / Accepted: 4 February 2013 / Published online: 17 February 2013 # Springer Science+Business Media Dordrecht 2013 Abstract This paper presents an investment feasibility analysis of rainwater harvest- ing systems for the residential sector in Santa Catarina State, southern Brazil. Five towns were selected for the analysis. Daily rainfall data, average water consumption, rainwater tank costs, water pump costs, and water, sewage and electricity tariffs were obtained for the five towns. Different values for the roof area, number of residents, potable water demand, and rainwater demand were analysed. The rainwater tank capacities were estimated using the Netuno computer programme. The investment feasibility analysis was performed considering the ideal lower tank capacity, as well as capacities smaller and larger than the ideal. Such capacities were obtained accord- ing to a variation of six months in the payback period. It was observed that the ideal tank capacity can be conservative for high rainwater demands. In such cases, an investment feasibility analysis should be performed in order to obtain a more appropriate tank capacity. The main conclusion is that rainwater usage is economi- cally feasible for most cases; and the higher the rainwater demand, the higher the feasibility. Keywords Rainwater usage . Rainwater tank sizing . Houses . Investment feasibility analysis 1 Introduction The use of rainwater as a strategy to address the problems related to the availability of potable water and to reduce its demand has been studied by many researchers in different countries. Examples found in the literature include studies on the use of rainwater in hotels in China (Deng 2003), in schools in Taiwan (Cheng 2003; Cheng and Hong 2004), in single and multi-family residences in Germany (Herrmann and Schmida 1999), in single-family residences in Australia (Coombes et al. 1999; Imteaz Water Resour Manage (2013) 27:2555–2576 DOI 10.1007/s11269-013-0303-6 E. Ghisi (*) : P. N. Schondermark Department of Civil Engineering, Laboratory of Energy Efficiency in Buildings, Federal University of Santa Catarina, 88040-900 Florianópolis, SC, Brazil e-mail: enedir@labeee.ufsc.br