Depends on the size of battery backup and number of things hooked up to it. You have to calculate the watts of each item hooked up against the capacity of your battery backup. Normally each battery back has a chart of time on the box. Hope it helps.
Installed late October 2017 - I was initially impressed with the space savings with this power supply. It was a good product for 18 months, then started to burn out slowly. It finally failed on May 31, 2019. A couple of rectifiers burnt up before the power supply fuse blew, but it did protect all the camera banks (channels). Back to the original spaghetti set-up, as I'm still undecided if I'm going to replace. ~ Keith M. ~
i have used this for many basic 16 camera systems and it works great, if you need more power for PTZ or long runs you can do 2 of the 8 camera power supply's for some reason they are actually higher amperage on 8 then they have for,the 16 so 2 of them are much more powerful.. but only if you need the extra, because this one powers most without a sweat.