This study was accomplished using 26 locations in the major ecological zones of Nigeria as well as different classes of residential buildings and different levels of water consumption. For each location, house dwelling class and level of water consumption, a water balance approach was used to assess the proportion of water demand that can be met by rainwater. Results obtained indicate that for all the locations in the rainforest zone and some parts in the guinea savanna zone, over eighty percent (80 %) of water demand of those living in bungalows can be met by rainwater. Rainwater harvesting potential was found to be a power function of rainfall coefficient of variation, with coefficient alpha and exponent beta. High correlation coefficients (0.881 a parts per thousand currency signaEuro parts per thousand R (2) a parts per thousand currency signaEuro parts per thousand 1) were obtained between coefficient alpha and roof area per capita. Also, high correlation coefficients (0.847 a parts per thousand currency signaEuro parts per thousand R (2) a parts per thousand currency signaEuro parts per thousand 0.992) were obtained between exponent beta and roof area per capita.