On Sun, 29 Jul 2018 14:27:55 +0100, Tim Watts wrote:

====snip====


APC's SmartUPS 1000 claims 97% efficiency.

I suspect that figure is for the DC to AC conversion efficiency of the
sine wave inverter. However, assuming they've expressed the ratio of
maintainance consumption to maximum power output as an 'efficiency'
percentage (I'm guessing the 1000 is the VA rating making the wattage
rating 750W on the assumption of a PF figure of 75% for the VA rating
being used), that would imply a standby power consumption circa 22.5
watts (or 24 watts for 800W at a less generous 80% PF rating).

Using the same basis to calculate the SmartUPS700 'efficiency rating'
would give a figure of 96% and for the SmartUPS2000, a figure of 97.7%. I
somehow don't think that 97% efficiency figure relates to what you think
it does.

The only other type of UPS where such an efficiency figure would be
significant is the no-break type where power to the protected load is
provided from the inverter at all times. I'm pretty certain the
SmartUPS1000 is just another line interactive UPS just like the
SmartUPS700 and SmartUPS2000 models.


Let's be uncharitable and say a typical UPS is 90% and your IT load is
100W (that's a lot, an HP Microserver Gen8 is quoted at 50W - so I am
adding a switch, modem and HA embedded controller.

Your wastage there would be 10W.

At 15p/unit that is 3.6p/day or £13/year.

In over half the year, that heat is probably not wasted (contributing to
home heating).

If the APC get's better than 95%, halve the above.

It's a very small number in the grand scheme of things.

If that 3% energy loss is for when the SmartUPS1000 is passing mains
power through to a load at the maximum rating, you can't apply a linear
efficiency calculation for fractional loadings since it must include the
fixed maintainance consumption leading to an efficiency figure of just
30% or so for a 10W load (or just 1% for a 1W load). The real concern is
down to the cost of just keeping it plugged into the mains without any
load connected or switched on. I think you need to determine exactly what
APC mean by "An efficiency of 97%" before you try working out such TCO
figures. :-)

--
Johnny B Good