A:Answer I know COMCAST rents them to users who rent a comparable Netgear unit, but the Comcast guy said they get a flow of returns / replacements. I did research on AMAZON and found complaints ... the battery backup units didn't hold a charge very long, or such. They are pretty small. So I purchased and connected to my CV7100 a larger and more robust APC BACK-UPS Connect model BGE90M 120 V Network backup (with USB charging ports) for a little over $30. It had much better reviews, has more power, is about 1/2 the size of a shoe box, has a built in lightweight surge protector, has three output two prong plugs, allegedly runs 4.5 hours, and has an ON OFF switch so that if the power goes out, you can ration battery power to simply run your VOIP and MODEM/ROUTER functions. The internal sealed lead acid battery is replaceable. Wt est 7 lbs. Much better than the insertable junk that fits inside the Netgear. So far so good.