The capacity credit of wind power expresses how much 'conventional' power can be avoided or replaced by wind power. From data available in the literature, we have designed an analytical formula for the capacity credit based on the penetration level of the wind power in the power system, the overall capacity factor or annual use of the wind turbines, the reliability of the conventional part of the power system and the spread of the wind turbines. The resulting analytical formula avoids the use of elaborate stochastic reliability evaluations in providing a quick estimate of the capacity credit. (c) 2005 Elsevier Ltd. All rights reserved.