This paper looks at Energy Savings Obligations in the UK. More specifically, it discusses how the policy instrument changed over time and what the drivers of that change were. The UK was the first country in Europe that introduced obligations on suppliers to save energy at the customer end in 1994. Since then this policy changed rapidly and is now the principal instrument to deliver energy savings in the housing stock. The paper aims to answer three questions: First, how did the policy instrument change over time? Second, what were the key drivers of that change? Third, how did those pressures filter through the policy process and affect the energy savings obligations?