The differences that methods make: Cross-border power flows and accounting for carbon emissions from electricity use

How much carbon was emitted due to consumption of electricity in each US state in 1999? This paper presents three alternative methods for answering this question, each of which is conceptually sound and sums to the same national total, yet each produces very different estimates of individual state emissions. These differences result from alternative assumptions taken to account for emissions associated with interstate electricity trade-power, and hence emissions, produced in one state but consumed in another. The methods described here demonstrate large effects that alternative methodological choices can have on our understanding of a state's carbon emissions levels, and on the incentive structures for states to enact supply and/or demand-side carbon reduction policies. Of the three methodologies, one is characteristic of standard carbon emissions accounting practice, one of life-cycle assessment, and one is an integrated approach, of which I argue that it is superior because it registers state carbon emissions change arising from change in both electricity production and consumption, thus creating incentive for states to enact a full range of progressive energy policies. Though developed here at the state scale, the issues engaged are relevant to carbon analysis and policy formation at scales ranging from the local to the international.