In recent years, heat pumps have emerged as a promising new form of technology with a relatively low environmental impact. Moreover, they have presented householders with an opportunity to reduce their heating bills. Heat pumps can heat a building by 'pumping' heat from either the ground or the air outside: an intriguing process which utilizes principles that are somewhat analogous to those employed in the domestic refrigerator. Armed with the practical information contained in these pages, homeowners will have the necessary knowledge to take advantage of this potentially low-carbon technology to heat their properties.

John Cantor studied mechanical engineering and started life in the refrigeration industry. A keen environmentalist and practical engineer, he became interested in heat pumps in the early 1980s and designed and built three ambitious projects heating community swimming pools. He was a heat pump inspector for the first round of government Clear Skies grant initiatives, has tutored a number of heat pump courses and has written many articles on the subject. Gavin D J Harper writes extensively on substainability issues and is currently researching the subject of green business models for sustainability for a PhD at Cardiff University Business School. Gavin is a member of the Institute of Engineering and Technology, and holds two honours degrees from the Open University and three masters degrees. He is the author/co-author of two books for Crowood, Domestic Solar Energy and Small-Scale Wind Power Generation.