Rooftop solar panels generally have a shorter payback period than a battery because they can reduce daytime grid purchases at a lower upfront cost. Your actual result depends on system price, electricity use, feed-in tariff, export limits, orientation, shading and future energy prices. A battery may improve savings by storing surplus solar for evening use, but its extra cost, usable capacity, warranty and replacement risk can lengthen the overall payback period. Compare installer quotes using your own interval electricity data, and ask a qualified installer to show estimated savings under conservative assumptions.