UPS for ReadyNAS 6 + ReadyNAS Duo

Great advice, thanks guys. Ok I've done some more research.

First, on the ReadyNAS themselves - the official comparison published by Netgear puts the (newer generation) devices at 24.2W for the Duo and either 74W or 82W for the Ultra 6 (measured with 6 x unspecified 2TB drives), so I'll assume my older generation devices are not much different. I found another thread where someone had checked the actual reported UPS power draw on their Duo v1, and clocked it at 30-35W:

http://www.readynas.com/forum/viewtopic.php?f=21&t=62662

Now, about the drives - you're definitely right - the Hitachi 7K3000's I have apparently give better performance at the cost of quite a bit more power consumption - according to this report, 9.1W each at idle, and 10.1W not idle:

http://techreport.com/review/20562/hitachi-deskstar-7k3000-3tb-hard-drive/9

That's about 50% more power consumption than the 3TB WD Caviar Green drives :( maybe I should have thought about that before dishing out for these, oh well it's a bit late now.

So I assume we can add this all up to get a reasonable guess-timate? My Duo has normal 2TB WD Caviar Greens (WD20EARS) so I'll assume I have the expected power consumption on that - let's say not worse than 35W the guy above found. For my Pro with 6 of these Hitachi drives, let's say it's 6 x 10W = 60W, plus whatever overhead for the device itself. Assume the worst case from above, 82W, minus the nominal usage of WD Caviar Green 2TBs which could be at least 6W each, so that gives us 6 x 6W = 36W. So subtract the 36W and we can say our ReadyNAS Pro on it's own might get up to 46W. Then add our Hitachi drives 60W, and that gives us 106W. I think I'm being pessimistic here. Also, checked on the GS108T switch, looks like less than 8W max. Then let's say I've got a 90W (worst case) laptop charger also.

So add it all up, for worst expected normal consumption:

ReadyNAS Duo + 2x2TB WD Caviar Green drives : 35W
ReadyNAS Pro + 6x3TB Hitachi drives : 106W
GS108T Switch : 8W
Laptop : 90W

So far we are up to 239W expected consumption.

Consider worst case absolute maximum requirement:

ReadyNAS Duo : 60W
ReadyNAS Pro : 300W
Switch : still 8W
Laptop : still 90W

That gets us up to 458W. I assume we can't possibly exceed that, right?

So I guess this means we need something capable of providing 5-10 mins backup at least for up to about 250W, and handling perhaps a max spike up to 450W? Or do I not really care about the maximum consumption?

Am I thinking in the right way about all of this? Do I need to be considering VA instead of just Watts? Since UPS seem to be rated in VA...