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The financial viability of a rainwater harvesting (RWH) system is highly determined by regional conditions such as rainfall pattern and water prices. Successful implementation of rainwater harvesting systems depends largely on the identification of suitable sites. This paper presents the water saving potential and economic effectiveness of rainwater harvesting systems across eight major cities in China, using a daily water balance model. Results show six to 81 days (or 1.6% to 22.2%) of dependability can be achieved by using a rainwater harvesting system over these cities. The annual water saving efficiency ranges from 10% to 37% and the benefit–cost ratio varies between 0.45 and 1.20 across the studied cities. South China achieves the maximum annual water saving and the highest benefit–cost ratio, while southeast China has the most regular profile of precipitation use. Northwest China was found to be the region with the worst performance, both in yearly water saving and in regularity of rainwater use on a yearly scale. It was also found that the RWH system is not financially feasible in the northeast, southwest and central plains due to the benefit–cost ratios being smaller than 1.0. HIGHLIGHTS RWH systems have the best water saving and financial fits for southern China.; The northwest is ranked as having the lowest annual water saving.; Southeast China (represented by Hangzhou) has the most regular profile of rainwater use.;