Energy policy goals across many countries and regions seek to achieve multiple goals simultaneously, including to reduce emissions, improve energy security and enhance energy affordability. A further goal is that energy policy should make a positive contribution to economic development of the area, or that (at least) energy policy changes should not worsen economic outcomes. It is the contention of this thesis is that ex ante multi-sectoral economic modelling approaches - specifically, Input-Output (IO), Social Accounting Matrix (SAM) and Computable General Equilibrium (CGE) analysis - can usefully explore the potential economic and environmental consequences of energy technologies and policies. Specifically, these models can assist in identifying and quantifying the impact of policies on the competing goals of energy policy, and so improve the design of appropriate energy policy. The thesis consists of six papers which apply multi-sectoral modelling approaches, all of which were published in peer-reviewed academic journals between 2007 and 2015 (inclusive). Each paper describes and/or extends multi-sectoral empirical economic analysis and modelling. The applications range from specific energy technologies - an onshore windfarm development, biofuels and developments in marine renewable energy technology - to potential energy policies - a (revenue-neutral) carbon tax and improvements in the efficiency of energy in production. This thesis explores the fundamental characteristics, assumptions and uses of "fixed" and "flex-" price models. Working sequentially from IO and SAM to CGE methods, it explores the particular strengths, weaknesses and usefulness of each of these modelling approaches, and explains the contribution of the papers included in this PhD by published works to the academic literature and pertinent policy issues.