Reducing the City\'s Carbon Footprint: An Investigation of Solar Water Heaters and the Rebound Effect in Cape Town Social Housing

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Solar Water Heaters (SWHs) can have extremely short greenhouse gas emission payback periods as shown in various life cycle studies. Thus, it is believed that replacing electric geysers with SWHs will reduce a household\'s carbon footprint. This conclusion, however, does not take the rebound effect into account, where money saved from spending less on electricity for water heating, is spent eventually, either on more electricity, or on other goods and services with an associated carbon footprint. Previous studies conducted on the low-income areas of Kuyasa (Cape Town) and Zanemvula (Nelson Mandela Bay) confirm that for this income bracket the suppressed demand for electricity is so great that the installation of SWHs fails to produce a significant reduction in electricity consumption, confirming the "suppressed demand hypothesis" which provides an accepted basis to classify such projects as sustainable development cases worthy of receiving climate finance. An optimistic assumption about the future of South African cities must however recognise significant upward mobility, which leads to the question of whether SWHs result in a significant decrease in the carbon footprint of households in higher income brackets. The "gap" housing market consists of households that earn ZAR 3500 - 7500 per month: they earn too much to qualify for a Government housing subsidy, but most cannot afford housing in the private sector. Recent social housing projects, providing rental stock for this market, including Steenvilla and Drommedaris in Cape Town, have included SWHs. This work aims to answer the following questions: Does the installation of SWHs in gap social housing schemes result in these households consuming less electricity than households of the same income using electric geysers? If so, what do these households spend this saved money on and how does the carbon footprint of these new goods and services compare? The methodology includes surveys to investigate the electricity consumption and spending habits between Cape Town social housing schemes that use solar water heaters and those that have conventional geysers. Quantitative data on electricity purchases are also used. Preliminary results suggest that for households earning an average of ZAR 6000 per month, electricity consumption is reduced by approximately 120 kWh/month when SWHs are installed. Survey data suggests that saved money is spent on a wide range of goods and services. The household carbon footprint is however reduced as these goods and services have a lower carbon intensity (at ~ 0.3 kg CO2eq/ZAR) than South African electricity (at ~ 1 kg CO2eq/ZAR).