Berkeley Lab’s Tracking the Sun report series is dedicated to summarizing trends in the installed price of grid-connected, residential and non-residential systems solar photovoltaic (PV) systems in the United States. The present report, the ninth edition in the series, focuses on systems installed through year-end 2015, with preliminary data for the first half of 2016. The report provides an overview of both long-term and more-recent trends, highlighting key drivers for installed price declines over different time horizons. The report also extensively characterizes the widespread variability in system pricing, comparing installed prices across states, market segments, installers, and various system and technology characteristics. The trends described in this report derive from project-level data collected by state agencies and utilities that administer PV incentive programs, solar renewable energy credit (SREC) registration systems, or interconnection processes. In total, data for this report were compiled and cleaned for more than 820,000 individual PV systems, though the analysis in the report is based on a subset of that sample, consisting of roughly 450,000 systems with available installed price data. For the first time, the full underlying dataset of project-level data (excluding any confidential information) is available in a public data file, for use by other researchers and analysts.