A B S T R A C TResidential electrical load in Iraq can be divided into five components, lighting, home appliances, heating, cooling, and water heating. Water heating component represents the largest residential electric load component in Iraq. The current research aims to test the possibility of using solar water heaters to supply hot water to residential units. Solar water heaters were added to a number of residential units in Mosul city, with the addition of a small electrical heater to provide supplementary heating. The readings of the total energy consumed, the energy consumed in the supplementary heating, the amount of water consumed and the water temperature in the solar heated tank, were recorded each day for a full year. The results were analyzed and compared with the case without the addition of solar heaters. The addition of solar water heater with supplementary heating leads to the reduction of the total consumption up to one-fifth of the total energy (19.19%).