In the last year, storage prices have fallen 16 percent, setting a new all-time low. Driven by falling raw material costs, it has never been less expensive to add storage along with your solar system. This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www. Ramasamy, Vignesh, Jarett Zuboy, Michael Woodhouse, Eric O'Shaughnessy, David Feldman, Jal Desai, Andy Walker, Robert Margolis, and Paul Basore. Solar Photovoltaic. Evaluating solar energy storage systems requires consideration of multiple factors: power rating, usable storage capacity, round-trip efficiency, warranties, cost, and battery lifespan. Lead-acid and lithium-ion constitute the two most frequently deployed battery types for solar energy storage. Each year, the U. Department of Energy (DOE) Solar Energy Technologies Office (SETO) and its national laboratory partners analyze cost data for U. solar photovoltaic (PV) systems to develop cost benchmarks. These benchmarks help measure progress toward goals for reducing solar electricity costs. The most common storage technology used in solar plants today is lithium-ion batteries, particularly LFP (Lithium Iron Phosphate), thanks to their safety, longevity, and favourable cost-performance ratio.