The latest annual report from Berkeley Lab on in trends among grid-connected, distributed solar photovoltaic (PV) systems in the United States found that solar panel prices are continuing to drop as systems grow bigger and more efficient. National median installed prices in 2018 were $3.7/W for residential, $3.0/W for small non-residential, and $2.4/W for large non-residential systems.
Some systems carry considerably lower prices. Factors accounting for price variability include differences in system size, module- and inverter-type, mounting-type, location, installer, host customer-type, and new construction vs. retrofits. Solar storage system installations were up considerably in 2018 compared to previous years in several states, reaching about 5% of the solar PV market in California most notably.