San Diego has some of the most expensive water in California – and in the country. A typical San Diego household pays about $80 a month for water. The national average is less than $40 a month, according to a recent survey by the American Water Works Association. Water in California is more expensive than elsewhere, but San Diego still has among the highest rates in the state, according to another recent survey. The most expensive water in the state is found in communities along the state’s Central Coast, like Santa Barbara.