mdf:
We were affected by the Wellington South power cut too. In the interests of preventing another Lord of the Flies scenario the next time this happens, I'm shopping for a UPS too.
Constant Vigil product looks great. If I understand this right, it is 240V --> 12V battery --> 12V router + ONT?
However our wifi is from cabled WAPs run off a POE switch. Is there an equivalent product for POE (which is 48V I think) that isn't cost-prohibitive? As I understand it, cheap (sub-$1000) UPS are more designed for a few minutes of runtime to have a managed/orderly shutdown rather than actually running something off batteries for a decent chunk of time?
The principle of the Constant Vigil hardware is to maintain the supply to low voltage (12 volts or less) relatively low power consumption units such as an ONT or router, rather than using a UPS to maintain 230v AC supply. I would encourage you to use the 'Contact' tab (Contact – Constant Vigil) to initiate a discussion with them - they may well be able to do something for your POE hardware.