Uninterruptible Power Supplies (UPS) are also inverters, but with cheaper built-in lead-acid batteries. They are meant to regulate power to devices in case of power surges and keep devices going until alternative power is restored, like a generator. An online UPS will continuously draw power from batteries, meaning there is no switching or time delays. However this will reduce lifetime of the batteries. An offline UPS directly supplies AC power from load and switching to battery during power failures in less than 6ms, which is usually enough to keep your device going.

Inverters with batteries are usually larger and more expensive. These are installed as alternatives to generators, and at times with solar panels, to keep devices on for longer periods.