This document catalogs the characteristics of current and potential future direct current (DC) products and power systems. It is part of a larger U.S. Department of Energy-funded project, "Direct-DC Power Systems for Energy Efficiency and Renewable Energy Integration with a Residential and Small Commercial Focus". That project is investigating the energy-savings potential, benefits, and barriers of using DC generated by on-site renewable energy systems directly in its DC form, rather than converting it first to alternating current (AC) for distribution to loads. Two related reports resulted from this work: this Catalog and a companion report that addresses direct-DC energy savings in U.S. residential buildings.Interest in 'direct-DC' is motivated by a combination of factors: the very rapid increase in residential and commercial photovoltaic (PV) power systems in the United States; the rapid expansion in the current and expected future use of energy efficient products that utilize DC power internally; the demonstrated energy savings of direct-DC in commercial data centers; and the current emergence of direct-DC power standards and products designed for grid-connected residential and commercial products. Based on an in-depth study of DC appliances and power systems, we assessed off-grid markets for DC appliances, the DC compatibility of mainstream electricity end-uses, and the emerging mainstream market for direct-DC appliances and power systems.