季节性附加费是在高峰需求期间（通常是夏季）施加的基准水价的预定增量。超额使用费（或附加费）的一个有益方面是，它往往会导致个人客户更公平地承担成本。制定附加费的一个考虑因素是对过度使用的适当定义。关于季节性费率对高峰系统需求的影响，还有许多未知数。价格信号应反映出在季节性需求期间提供额外有限容量的边际成本，不鼓励消费可季节性使用的那部分可自由支配的水，并出现在总体需求曲线的该部分，代表对价格变化的更大响应。本文给出了制定和实施季节性附加费的基本背景信息，并以宾夕法尼亚州的一个案例进行了说明。

A seasonal surcharge is a predetermined increment to the base water rate, which is imposed during the period of peak demand, usually summertime. A beneficial aspect of an excess-use charge (or surcharge) is that it tends to result in a more equitable bearing of cost by individual customers. One consideration in developing surcharges is a suitable definition for excess use. There are a number of unknowns regarding the effect of seasonal rates on peak system demands. Price signals should reflect the marginal cost of providing additional limited capacity during seasonal demand periods, discourage consumption of that portion of discretionary water that may be used seasonally, and occur at that segment of the overall demand curve representing greater responsiveness to changes in price. Basic background information on formulating and implementing seasonal surcharges is given, using a case study in Pennsylvania to illustrate.