The WELC programme, which is written in microsoft BASIC for a BBC microcomputer, is a pre-feasibility cost estimating procedure for U.K. low-enthalpy geothermal wells with depths between 1000 and 4000 metres. The programme provides estimates of total drilling time and total costs, each with a breakdown into contributing components. A substantial amount of default data are incorporated into a programme which enables the user to operate it with limited information, as appropriate to an early stage of assessment, or pre-feasibility study. The minimum information required consists of total vertical well depth, total vertical depth to the top of the aquifer, type of well (straight or deviated, production or re-inject;on) , the method of completion (open hole, slotted liner, or mild or stainless steel screen), and rock hardness classification (soft, medium, medium-hard, or hard). When default data are chosen for the price of drilling supplies and services total well costs are calculated in £ sterling at early 1983 levels. The programme can accept a considerable variety of user's own data and, if suitable information is provided, total costs can be determined for different years and in different currencies