Preprint and supplement of "Tracking physical delivery of electricity from generators to loads with power flow tracing" Abstract: We use power flow tracing to measure the physical delivery of power between all generators and loads in models of the European and Eastern U.S. transmission grids. We believe this is the first work to measure physical delivery on high resolution models of real transmission grids. Physical delivery analysis can inform the integration of delivery requirements into clean energy procurement guidelines, such as those in the Greenhouse Gas Protocol (GHGP) standard, to support credible claims. We propose three new metrics to summarize physical delivery across a transmission grid: delivery distance (median distance traveled by power), expected deliverability (generator/load pairs which meet a physical delivery cutoff), and regional connectivity (which uses modularity, a metric from graph theory, to summarize how well boundaries align with physical delivery). We evaluate these metrics across Europe and the Eastern U.S.. We find that the distance and direction traveled by power is highly variable, and can be partially explained by patterns of power flow from large generation centers towards large load centers. We evaluate how existing boundaries align with physical delivery and find that bidding zones and countries in Europe and states in the Eastern U.S. perform better than other options.