There's another size too: community-scale or neighborhood batteries, which are growing rapidly in Australia due to support from state governments like Victoria and Western Australia and, more recently, from the federal government. They seem to solve a lot of problems we know people are concerned about—such as enabling more rooftop solar and helping to speed up a transition to renewables.

But the popularity of these batteries shouldn't be the only factor in decisions about where they are rolled out. Sometimes—and in some parts of the grid—they make sense. At other times, they may not be the best solution.

Our research explores when community batteries are—and are not—useful. In short, we find the main use of these batteries is to make the grid able to handle more solar and electric vehicles. But they're not the only option. This is why we have produced a decision-making tool for policymakers to figure out where and when these batteries are worthwhile.