As phone providers like AT&T and Verizon seek to phase out copper telephone networks in favor of fiber- and wireless-based VoIP (Voice over Internet Protocol) services, the Federal Communications Commission must consider whether to require home phones to work during power outages.

Federal Communications Commission Chairman Tom Wheeler has decided what the requirement should be—carriers will have to offer 24-hour backup systems, but they'll be able to charge consumers for the batteries.

Wheeler circulated his proposal to fellow commissioners on Friday and will put it to a vote on August 6. If it's approved in its current form, VoIP providers will have to offer 8-hour backup systems immediately and 24-hour backups within three years.

The new rules would apply not just to legacy voice providers with copper networks, but to any home VoIP service, such as those offered by cable companies.

"Traditional, copper-based landline home phone service typically works during electric outages because the service provides its own power, but modern substitutes usually need backup power to keep operating during a power outage," said an FCC fact sheet on Wheeler's proposal. "If adopted, these rules would require providers of these substitutes, such as a cable company’s bundled voice service, to offer consumers the option to buy backup power so they can use their home phones during power outages."

Maintaining 911 service during long power outages is one of the main goals.

There shouldn't be any technical limitations that would prevent implementation. Verizon already sells its fiber customers a $40 battery that can power voice service (either VoIP or traditional landline service over fiber) for "up to 8 hours" during an electric outage.

Verizon also offers a longer-term "PowerReserve" backup device that works only with newer versions of its home fiber equipment; Verizon has quoted its backup time in various places as "up to 20 hours" and "up to 24 hours." This device reportedly also costs $40, but "when we migrate a customer from copper to fiber for their voice service, the PowerReserve is free," Verizon told Ars. The system requires 12 D-Cell batteries, which must be purchased separately. Customers could extend the time it works during power outages by buying extra batteries or turning it off when it's not in use.

Customers would not be required to buy backup systems, but they must be told of their options. Under Wheeler's proposal, phone providers would have to "inform both current and new customers about service limitations during electric outages and the steps they can take to address those risks through backup power, including how to keep their service operational during a multi-day power outage. This action would empower consumers to make informed choices and support their need for 911 service during emergencies."

Separately, the FCC is also considering whether to require carriers to provide three months' notice to residential customers before discontinuing copper-based service. Currently, the providers don't have to provide customers any notice if they're being switched from copper to something else, as long as landline voice service remains available over the new network.

AT&T and Verizon have been criticized by customers and consumer advocacy groups for allegedly letting copper networks fall into disrepair, forcing customers off the old phone system.