energy-efficient uninterruptible power supplies?

 So, around here we've been having a lot of storms lately, and I've been
thinking of getting an uninterruptible power supply (UPS) for my computer.
I've avoided getting one for a long time, but they're cheap now, and
the only thing holding me back is power usage.  Specifically, if (say)
500W comes out of one of them, how much needs to go in?

Obviously some power must go to keep the battery charged (as even when
sitting on a shelf, a battery will discharge slowly), but that could be
a very small amount.  Do modern consumer UPSes use much power for
anything else?  I believe there are two types of UPSes -- those where
the battery is always in the circuit (and there is an AC->DC->AC
conversion) and those where the battery is in the circuit only when
necessary.  But, I don't know which kind is in common use in consumer
UPSes.  It seems like the latter type would be more energy-efficient.

Are we talking about losses of 10%?  20%?  1%?

   - Logan

 

thinking of getting an

for a long time, but

Specifically, if (say)

Depends on how it works.

The ones that change over on power failure arent too bad
at all because the extra power is only used to replace what
leaks away from the batterys over time, and that isnt much.

The best type that supplys the batterys all the time and powers
what you are powering from it from the batterys all the time are
limited by that conversion efficiency and thats much worse, you're
going to be putting more than 20% more into it than you get out.


on a shelf, a

Yes it is.


the circuit (and

circuit only when

Correct.


The later. The former are more common with commercial UPSs.


20%+ with the always on type, 1% with the switching type.

 
The logic and power line monitoring circuitry, relay coils, etc. may
pull 1-5W, regardless of attached load.



There is a third, intermediate type, often called "Line Interactive"
(e.g. APC Smart-UPS, or the old Best Power Fortress models), which
feeds the power through a transformer full-time (with switchable taps
to allow boosting voltage during a brownout, or bucking a minor
overvoltage, without using the battery).  These also keep their
inverter in a standby mode, where it tracks the power line phase to
allow faster switching.

Both line-interactive aspects consume some extra standby power,
although far less than a "true online" unit-- usually about 20-30W.

The cheapest low-end models tend to lack these ameneties, an so
consume less power... usually less than 10 W.



For low-end, "offline" units, the extra power will be mostly a
constant value, rather than a percentage of load... usually 5-10W, up
to 20-30W for larger, more sophisticated units.

Whenever your computer's completely shut down (not in sleep mode), it
may be worthwhile to also turn off the UPS, cutting its standby load
down to 0-1W.  That opened switch or relay between the computer &
power line is also a bit of extra protection against power line
spikes.
--
Jordan.

 On Jun 27, 6:17 pm, j...@VictorTangoEleven.net.invalid (Jordan Hazen)
wrote:

Shoot, don't talk about UPS and power spikes, or surge protection,
etc. or you know who will appear in here talking about whole house
blah blah blah.

 

I don't know if this technically qualifies as an UPS, but for my job the
company issues me a laptop.  The machine of course comes with a battery, and
the battery charges whenever the machine is in the docking station (at work)
or plugged into the adaptor (at home).  When the power fails, the laptop
doesn't even blink.  The external monitor goes dark, of course, but the
laptop screen stays up and running, and nothing's lost.