People and businesses can be encouraged by targeted policies to change their behaviour around using energy and energy efficient technologies. Policy tools such as regulations, standards and financial instruments can lower energy demand, and result in health and economic co-benefits. AVOID 2 ran two model simulations of the effect of energy efficiency policies on the cost of limiting global warming to below 2°C. One simulation shows that, at the global-scale, policies that introduce financial incentives to take up energy efficiency measures reduce the overall cost of mitigation by around 40%. Another, separate, simulation shows that the cost of mitigation could be reduced by almost 25% as a result of policy-induced behavioural changes in heating and transport usage.