In most cases, no. VoIP phone systems rely on an internet connection. During a power outage, your router will not be able to function, meaning you will lose internet access. Equipping your router with a backup power source can keep your phone system online in the event of a power outage. The good news is that Ringover’s mobile app can support you during a power outage as long as your smartphone has sufficient battery life and an active data plan (preferably 4G).