APC Smart-UPS C Series 1000~1500VA inaccurate LCD Status Power meter - Details

[Kiriakos GR]

At 2017 I did receive an APC SMC1500I ( I assume the last model number translates to EU), either way SMC1000 or SMC1500 or SMC1500-2U, all are identical regarding use of specific LCD Status Power meter.

Today I did run some power measurement tests at my own APC SMC1500I,  comparison point this was my plug-in budget power meter, which appears to be sensitive at no less than 1W of load.
This side by side comparison gave useful clues.

I did spend over two hours at testing several loads, and I will divide test conclusions by electrical quantity.

Watts and VA
UPS LCD Status Power meter, this has severe difficulty to measure anything bellow 30Watts, UPS Watt / VA screen will shown zero power.
An single 60W light bulb this is enough load so the UPS to start measuring energy but the error this  is significant, UPS measurement 75 Watt.
Realistic measurements are possible for as long the load this increases at 100W and more.
At 150W you may start to trust the measurement.
at 300W load you may feel confidence that this is comparable value with other power meter.

AC Voltage measurement
110V or 230V those are high in volts electrical quantity, and only a very bad made budget volt meter will demonstrate 2% or higher as error.
UPS and also budget AC volt meter they come with 1% of error, and therefore there is nothing special there to talk about.
EU model voltage range 180 ~ 300V

 
AC Current measurement
APC SMC1500I this show unexpectedly insensitive at measuring AC current quantity, testing results at 390mA of load, UPS screen 0.3A.
Measurements started become realistic at 100W of load or higher (500mA or higher).

Frequency Hz
UPS this measure 49.97Hz when U1272A this was confirming 49.997 Hz.

UPS Load at percent reading
I could do an more in depth job if I had an xxxx thousands of euro digital AC load, but I do not own one.   
5.2% of load  this is the lesser recorded at my tests.   


APC
When I did receive APC SMC1500I (2017) I was impressed due it LCD Status Power meter, my older SUA-1000XL does not have similar circuit to measure watts.
And I did contact APC about asking details for the watt meter, and they did not answer back.
They were friendly talking about anything else than this topic.

APC UPS Watt VS VA sizing info
APC by Schneider Electric, this it does continue to name their models with VA (Volt/Ampere) in mind instead of Watts.
1000 VA model this is 600 Watts for continues use.
1500 VA model this is actually 1440 VA, even so due efficiency factor improvements, this is 900 Watts for continues use.   

20 years ago an computer power supply had much worst power factor than our times.
For example the average math for VA to Watts calculation that an UPS can deliver at max, this were calculated including PF 0.65 , when today Power Factor at PSU has improve to PF 0.80 and higher.
Low PF translates use of higher current in Ampere.
VA this is more realistic so us to discover the max AC current that a UPS electronics can handle.
Example No1:  240V +  Load 3.8A  high PF 1.00  = 912.0 Watts
Example No2:  240V + Load 3.8A  Low PF 0.65  = 592.8 Watts
Example No3:  240V + Load 3.8A  Low PF 0.95  = 866.4 Watts this is the most realistic wattage in our not perfect world.

In summary
No your UPS this can not be used as general use power meter, APC by Schneider Electric, they did cut lots of corners, when was selecting LCD Status Power meter circuitry, for their products.
And measuring error also expands at kW-hours that APC software trying to calculate as TOTAL Cost of Energy (Energy management -> Report).