ReadyNas 316 UPS recommendation

After a number of years with this, on units the size of the 316, I pony up and marry it to a APC SmartUPS 1500va. I purposely use a UPS that is perhaps a bit 'generous' for the NAS because the utilization and stress on the UPS stays low and thus the UPS batteries tend to last quite a while with quite extended periods of time (a couple of years) before I see any notice to replace the battery, and the UPS in my experience performs utterly reliably this way. Too small and they seem to go through batteries too frequently and need extra attention paid to them more than not.

314 and below do well enough with a APC 750 unit.

If this is for a business, that is what I would do. I'll understand if you go lower if this is in your home and you are keeping an eye on and paying your utility bills from your own pocket. At home I have 2 312 units, each married to their own APC SmartUPS 750's.

Yep, I use the 'Smart-UPS'. After doing this a number of years, some of those trying to 'cheap out' or take some shortcut or other, I've come full circle and have concluded that I'm getting tired of tweaking this, and fussing with that, or modding the other. I just want bone simple, solid, robust, reliable service and performance. Buy once, cry one.

Honestly, I'm not that impressed by the ES series. Those are more desktop oriented and even there they have not had the best history with me. I replace these more frequently than most others. I stopped buying them a few years back. YMMV. Again, if it's for business, get the more robust 'Smart-UPS', but if it's personal and you have to scrape your personal pennies together to get it, I understand, and then go with what is pocket friendly. BUT, do get a UPS hooked up to the NAS. The NAS will thank you.