This paper describes some aspects of prototype software designed to assist local authority planners and energy advisers in their efforts to increase the uptake of solar hot water systems in cities. To estimate the potential yield from installed systems, the Solar Energy Planning system implements an adaptation of the method for calculating the thermal performance of solar heating systems for domestic hot water in BS5918. A Mulch-enhanced version of the BREDEM-8 domestic energy model provides the basis for predicting the delivered energy savings. Reductions in CO2 emissions can also be quantified. A trial of the prototype in an urban area of Leicester, UK, is illustrated and some encouraging results are reported. (C) 2003 Elsevier Ltd. All rights reserved.