Domestic energy use accounts for more than a quarter of total energy use in the United Kingdom (UK), with space and water heating accounting for almost 80% of this consumption. Energy efficiency is often the simplest and most cost-effective way of reducing energy use, and improving domestic energy efficiency can contribute significantly to reducing the UK’s greenhouse gas (GHG) emissions. A significant proportion of the UK’s energy stock remains inefficient, and over 80% of current housing stock will still be standing in 2050. Therefore, retrofitting existing buildings is fundamental to achieving energy efficiency improvements in the domestic sector. In order to reduce carbon emissions and improve domestic energy efficiency, the UK government launched the Green Deal in 2013 to improve the energy efficiency in buildings in the UK, reduce emissions from homes by 29%, and help meet carbon reduction targets. It aimed to overcome existing perceived barriers to the adoption of energy efficiency measures in the home and enable households and businesses to make energy-saving improvements to their properties, delivering a range of important benefits to the owner/occupier as a result. This paper critically assesses the impact of the Green Deal in shaping pro-environmental behaviours by drawing on two case studies. Lessons learnt from the UK’s Green Deal energy policy are presented, and implications for the UK government’s role in shaping energy policy and pro-environmental behaviours are considered.