Area of outage costs and customer willingness to pay studies have been increased due to the growing competitive electricity market and increasing for demand. This thesis presents the methodology and main results for Saudi Arabia residential customers survey. The survey provided the cost estimates that have been incorporated in the quality of supply in terms of the cost of un-server kWh not supplied and damage costs. Customer willing to pay (WTP) has been evaluated for residential customer as well. As a part of this thesis, key performance indicators (KPI) have been calculated and compared to measured KPI in year 2007 for Saudi Arabia.