Off Grid Inverter Power Consumption & Efficiency

Author Message


Joined: 31/12/2016
Location: Australia
Posts: 874
Posted: 07:53am 17 Jan 2023      

I have been testing this for the last few days and taken short video clips so I can check it again and the numbers are the same, not surprised if the meters are a little out.

I have an old (2015 model) PIP 4048HS (Voltronic) inverter in the shed and the also the home built inverter, from the "Another Inverter Build" thread.

Its well known the idle consumption of 50w on these (used to be low cost) HF type inverter's is horrible on the 48v version.
So decided to see if it still holds true under load.
Idle at 54v =50w, this is not shown on the inverter display but a clamp meter will see the 1Amp from the battery, I Turn a heater on, that makes a 31A load at battery and display (confirmed with clamp meter), display watts 1.52kw out, battery volts 52.4, battery consumption  1624w = 100w loss.

Now the heater is at the end of the cable, perhaps 60m away, I connected a power meter close to the heater and it was reading 220vac  1480w so a loss of 40w, there is some power loss in this length of cable I can tell because it will warm up a little over time.

The home built inverter had 26w Idle consumption, ideal for standby and occasional Heavy motor starts, hands down beats the PIP 4048HS inverter in this situation for shed use, that's why I built it.

But The PIP 4048HS inverter might be a more efficient with loads of 500w to 1500w orso.
I might be building another inverter for the house with Peak efficiency between 300w to 1500w as thats where most of the loads are.

Anyone else have some different Peak Efficiency figures?
Cheers Aaron
Off The Grid


Joined: 17/10/2017
Location: Belgium
Posts: 373
Posted: 09:56pm 26 Jan 2023      

Aaron, I did some rough testing on my ozz inverter a few weeks ago, this were the numbers I noted, testing was done with especially resistive loads:
I had 4 meters at hand, 3 uni-T true RMS meters (current clamp type) and 1 extech true rms voltage meter.

The AC meter is a chinese front panel meter and is actually accurate.

Measurement 1:
on my AC meter 328W
with my clamp meter:
2.2A 237VAC --> 521.4VA
8.0A 52.1V --> 417W

With this power level there is a substantial part reactive power I guess, all switched power supplies with a bad power factor so it seems?

328/417W -->78%

Measurement 2:
on my AC meter 1335W

with my clamp meter:
5.92A 238VAC --> 1409VA
28.3A 51.85VDC --> 1468W

1335/1468 => 90.9%

Measurement 3
on my AC meter 2340W
on my clamp meter:
10A 239.5VAC -->  2395VA
48.6A 51.3VDC --> 2493.18W

2340/2493 => 93.8%

Measurement 4

On my AC meter 3765W
with my clamp meter:
15.8A 238.8V AC --> 3773VA
82.2A 49.7V --> 4085W
3765/4085 =>92.2%

Measurement 5:

on my AC meter 6122W
with my clamp meter
27.2A 224V AC --> 6160VA
142A 48.5V --> 6887W
6122/6887 => 89%

My inverter is completely powering my house, so it's a real life example.
I have some difficulties how I best calculate the efficiency of the inverter because of the reactive power involved. But I did with the worsted scenario. But either way it looks like my inverter has the highest efficiency around the 2500W mark.

The dropping of the voltage with higher loads has to do with the long cable run between inverter and battery. To be improved.
I don't think I can improve more, just maybe the filter inductor between H-bridge and transformer, it gets hot, it only has 30mm˛ wire I think



Joined: 31/12/2016
Location: Australia
Posts: 874
Posted: 09:58am 28 Jan 2023      

Thanks Nicks, that looks great.
Its interesting how it works out, the bigger loads are much better and inline with what I have been told when I started my build.
I see Measurement 1: at 78%   would be mostly inductive loads, and Measurement 3: is doing very well at 93.8%

Looking through some of my notes and photos from previous test runs, this is the Mad Inverter running in the shed, it has a C core type transformer, so not as good as a Toroidal transformer but still quite capable.
Some loads, measured at AC output and power used from battery.
137w ac    177w    =77%

500w ac   626w   =79%

1656w ac    1824w   =90%

2022w ac   2245w   =90%    Running a kettle to make a cup of coffee....

500 watts and lower, the efficiency gets clobbered, most of the house loads are within the 100w -500w range and running most of the time over night, large Fridge and a Deep freezer, and many other little things.
Not sure if I can improve on the lower wattage loads....will do some more testing in the future.


Joined: 17/10/2017
Location: Belgium
Posts: 373
Posted: 08:38am 15 Feb 2023      

I would look in to devices with bad power factor, improving this Will improve your efficiency. The quality of the series choke is important too. Warpspeed or wiseguy warned me about a too big airgap in my choke. And I think I noticed a higher loss then I calculated. You get something like fringing close to the Gap.wich eventually increase losses in the choke. Even with low load I notice a warm choke which is probably caused by circulating currents.