Energy efficiency first principle [2] is the acknowledgment that Europe's biggest domestic energy source is energy efficiency. It was first included in the European Commission’s Energy Union Strategy [3].

As an organising principle, “energy efficiency first”, applies to all policy-making and investment decisions and it includes:

• ensuring that energy saving solutions are not overlooked or undervalued;
• collecting reliable data which will allow to value the long-term economic, environmental and social costs and benefits of energy efficient solutions;
• removing barriers preventing energy efficiency improvements;
• developing and enforcing concrete policies, which will prioritize investment in energy efficiency.