• Storing electricity can be a boon to the system by reducing demand for generation and perhaps transmission capacity, but there are a number of variables in creating storage.
• The federal Energy Information Administration says a big factor is cost – some proven technologies like pumped storage and thermal are proven while others, such as batteries, are still evolving.
• Nonetheless, the EIA argues, "storage technologies offer price arbitrage opportunities and fast-response services that conventional technologies cannot match."

From the article:

Electricity storage can be deployed throughout an electric power system—functioning as generation, transmission, distribution, or end-use assets—an advantage when it comes to providing local solutions to a variety of issues. However, storage, particularly emerging technologies, may be expensive compared to other options.