What forces are today driving large property companies in Sweden to save energy and increase energy performance in buildings? This master thesis focusing on mandatory- and voluntary policy has used a Political Science perspective on Urban Planning questions. In this qualitative case-study, interviews were conducted with 7 out of the 10 biggest property companies in Sweden. It includes both an investigation into which policies are found to be relevant for companies as well as a discussion about which actors are pushing them to reduce energy and become more sustainable. Results show that companies make voluntary commitments that go beyond what current mandatory building- and energy regulations demand. Instead they use voluntary policy 25-35% below BBR-levels, mainly by using building certification Miljöbyggnad, to certify and communicate their efforts. All companies have energy targets published in yearly reports and continuously work to reduce their energy- and emissions output. Yearly reports also show that 6 out of 7 companies now use the Global Reporting Initiative (GRI). Some have joined benchmarking initiative GRESB or the CDP. The use of voluntary informational disclosure systems show that companies are under increasing pressure to become more (verifiably) sustainable.