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Outdoor water use is one of the components of household water use whose main purpose is irrigation. There are several previous studies that have estimated how much water is used for residential irrigation purposes, principally at the national level. However, estimates can vary from 30% to 64% as the percentages of total water use in a household that would be devoted for irrigation purposes. We established a methodology to estimate irrigation considering a range of impervious surfaces (5%, 15%, and 20%) and two established methods to estimate basic indoor water use, at the household scale. Monthly water billing records for Tampa and Orlando, Florida, were available from 2003 to 2007. These values were compared with a theoretical irrigation requirement calculated by a daily soil water balance equation to assess if homeowners were over-irrigating. Orlando showed higher values of estimated irrigation, compared to Tampa. Up to 76% of homeowner utility accounts over irrigated in Orlando, when the per capita method (to estimate indoor water use) was used. In Tampa, an average of 35% of households over irrigated. There was an inverse correlation between rainfall and estimated irrigation in Orlando, but not in Tampa.