Power cuts
A VoIP phone stops working when the power does
This is the honest limitation of every internet phone, ours included, and it is worth planning for rather than discovering.
A copper landline was powered from the telephone exchange. Your house could be dark and the phone still worked, which is why it was the thing you kept for emergencies. California has now authorized AT&T to retire copper service, so for a growing number of households that option is going away regardless of what anyone chooses.
An internet phone needs three things powered, and only two of them are yours:
Keep power flowing to these:
The handset, and if it runs on Power over Ethernet, the injector back at the router.
Your modem and router. This is the part people forget: the phone can be on a battery and still be useless because the router next to it is not.
Both are small loads. A modem and router together draw about as much as a light bulb, which is why a modest battery carries them a surprisingly long time.
Out of your control:
Your internet provider's equipment — the cabinet or node down the street. Providers put batteries in these, but you do not control them and you will not be told when they run out.
In practice this has been reliable for us, but it is the reason we will not tell you a backed-up house guarantees a working phone. It reduces the chance of losing service; it does not remove it.
What we run at home
An EcoFlow Delta battery on the modem and router, and nothing else on it. Network gear is a light enough load that a Delta carries it for a day or more, which is the whole point — it is the cheapest thing in the house to keep alive and the one that keeps the phone working.
A refrigerator is a different order of magnitude. Manufacturers publish an average daily figure and it is usually over a kilowatt-hour, so a Delta on a fridge is hours, not days. That is why ours runs the phone and the internet rather than the kitchen. Check the numbers against your own equipment before deciding what to plug in.
The Delta 3 Classic, Delta 3, and Delta 3 Max are the ones worth comparing, the Max being roughly double the capacity of the other two.
Disclosure: the link below is a referral. If you buy through it we receive EcoFlow credit, at no extra cost to you. We are telling you because a safety recommendation that quietly pays the person making it is worth less than one that says so.
Look at EcoFlow Delta batteries
And keep a mobile phone in the plan
Whatever you back up, a charged mobile is the fallback that does not depend on your house or your provider. If the person using this phone is a child, that is worth saying to them out loud rather than assuming: if the phone is dead and something is wrong, go find an adult or use a mobile.
