No, you do not need to have solar installed to install a battery storage system.  However, there are several benefits to pairing these systems with a solar system. Yes, you may install a battery that isn’t charged from a solar system. Your battery would charge from the grid and could provide power in the event of an outage. Note that metering and billing differs for solar + battery and standalone battery customers. Contact Eversource or UI with questions about billing and metering.