[Nut-upsuser] Recommended UPS to buy for use with NUT?

[Arjen de Korte]

Peter Selinger wrote:

>>>> I am running a home box (600watt total load, may expand to 800-900) and
>>>> I need a UPS that can sustain power to that for at least 20 min, but
>>>> I want as much time as I can get.
>>> Is that rated load, or actual load? That seems like an awful lot of
> 600 watt (or 600VA) does not strike me as an unduely large load rating
> for a UPS.

Please don't mix up VA and Watt ratings, they are very different things.

> My smallest UPS has 800 VA.

This is irrelevant when it comes to runtime. You can have an 800 VA UPS
with a Watt rating of just 10 Watts and a runtime of 1 second for
instance. Not very useful, but it is possible. The VA rating of a UPS
says nothing about the runtime.

> What did you have in mind Arjen?

As a summary from my previous post, you should consider both peak load
and average load when selecting a UPS. Just considering peak load, will
mean that you will select a way too big UPS if the average load is much
smaller, which is usually the case for computers. I have yet to see a
home computer system that draws more than about 50% of the full load on
average (and usually this figure is even lower).

> Also, 20 minutes runtime is not too much to ask.

Probably not, but at a load of 900W, conversion efficiency of 80% and
lifetime derating (due to aging of the battery) to 80%, this will
require a 1400 Wh of battery capacity (which is about 120Ah @ 12V, which
is a very large battery). You won't see many consumer grade UPSes with
that amount of battery storage installed (if there are any). Therefor my
question, if this is rated or actual (or better put, average) load?

> It's true that the system can shut down faster than that, but a human might
> appreciate a chance to save his work.

Of course. I'm not questioning the legitimacy of the need for a 20 min
runtime, it's the amount of power drawn that looks excessive.

Regards, Arjen