How much power does an Inverter use just sitting there idling?

[Joe Samra]

Just checked my SPF-5000-ES.
80.54 watts , at idle with fans running strong.
70.7 watts , at idle with fans running barely.
This is what it should be.

Would please let me know how did you do this test?

 

[Hedges]

I conducted a test the other, i turned on a small heater that draws 1A using only solar power, the AC output is a round 1A, when i turn on the AC input breaker i get 2 A on the AC input cable and 1A on the AC output, this is very weird and is confusing me. A friend of mine installed the same inverter, i asked him to test it, he gets also 2A on the AC input with no loads.
What could be the issue here?

It may be the inverter is drawing power to charge battery when AC is available.
Check battery current if you can. Otherwise, check battery voltage without/without AC from grid turned on.
If it is charging from grid, you may be able to program different behavior or battery voltage.

It is also possible the inverter presents a reactive load, is drawing current and VA but now power Watts. Some utility kWh meter might report power consumed even if it was all "reactive" power, zero real power.
You would need a device able to measure Power Factor or VA vs. W to tell. "Kill-a-watt" is one.

If the inverter presents an inductive load carrying 2A (which seems too high to me), adding a suitable capacitor could reduce that. That would be 23 microfarads if I did the math correctly. But it's not something I've ever tried, and first look for parts indicates it is not financially practical.

https://www.grainger.com/product/WEG-Power-Factor-Correction-Capacitor-16Y122

If the system is continuously consuming 460W, or causing an incorrect billing, that is obviously not good.

 

[timselectric]

Would please let me know how did you do this test?

No AC input or output.
No solar input.
Inverter powered by battery.
Checked battery amperage, with a clamp meter.
Checked battery voltage, with a multi meter.
Calculated wattage.

To get an accurate idle measurement. You need to make sure that the inverter isn't doing anything, except just sitting there and on.

 

[Joe Samra]

No AC input or output.
No solar input.
Inverter powered by battery.
Checked battery amperage, with a clamp meter.
Checked battery voltage, with a multi meter.
Calculated wattage.

To get an accurate idle measurement. You need to make sure that the inverter isn't doing anything, except just sitting there and on.

Thank you man for the info, i rechecked today you sing a multimeter in series with the input.
Solar input is off
Ac output breaker turned off
No batteries installed yet
AC input breaker is on, and still i get 2 amps.
Could you please try it my way, turn everything off including batteries and check the AC input current?
I really appreciate your help

 

[Joe Samra]

It may be the inverter is drawing power to charge battery when AC is available.
Check battery current if you can. Otherwise, check battery voltage without/without AC from grid turned on.
If it is charging from grid, you may be able to program different behavior or battery voltage.

It is also possible the inverter presents a reactive load, is drawing current and VA but now power Watts. Some utility kWh meter might report power consumed even if it was all "reactive" power, zero real power.
You would need a device able to measure Power Factor or VA vs. W to tell. "Kill-a-watt" is one.

If the inverter presents an inductive load carrying 2A (which seems too high to me), adding a suitable capacitor could reduce that. That would be 23 microfarads if I did the math correctly. But it's not something I've ever tried, and first look for parts indicates it is not financially practical.

https://www.grainger.com/product/WEG-Power-Factor-Correction-Capacitor-16Y122

If the system is continuously consuming 460W, or causing an incorrect billing, that is obviously not good.

Hello Hedges, actually yes i bought and installed this system to save some money and now it is the other way around.
I'm really disappointed with Growatt, and friend of mine also has the same problem, maybe it is this way when the AC input is on.
Next time im installing an off grid system i will test the AC input idle consumption at the electrical shop before purchasing.

 

[Hedges]

No batteries installed yet
AC input breaker is on, and still i get 2 amps.
Could you please try it my way, turn everything off including batteries and check the AC input current?

No AC input or output.
No solar input.
Inverter powered by battery.
Checked battery amperage, with a clamp meter.
Checked battery voltage, with a multi meter.
Calculated wattage.

Tim is using an AC/DC clamp ammeter (hall effect), can read DC current.

Joe has an AC only clamp ammeter (current transformer)

Possibly, "No batteries" has something to do with undesired behavior. Can you connect a batch of car batteries?
Then observe any difference in AC current, and read battery current with the AC scale you have (reads AC ripple but not DC.)

Tim - besides AC current in AC grid connection as requested, check AC current in battery cable (with and without grid connected).
I would expect that to be low under no load, but who knows. Likely has ripple when charging.
I find that when driving a large AC load from batteries, although battery DC (average) current matches load wattage, there is a large AC ripple. Capacitors can't buffer 60 Hz, only the higher frequencies of switcher. At least with my low-frequency inverter.

Joe - does your friend also have batteryless setup?
Without AC input, just PV, at least average current has to come from PV panels. Possibly peak current at top of sine wave. But I would guess a high frequency inverter would draw down capacitors to deliver peak current, at least in the batteryless case.

But I still don't know where 2A would be going. That's too much current draw on AC input when there isn't that much current on AC output.

This one?

Customized Solar Power System,Growatt Hybrid System,Split Phase PV System - Swtsolarpv.com

China supplier of solar system - off grid solar system,lithium battery storage system,solar power station offered by Sweet Power. Any questions,pls do not hesitate to contact us!

www.swtsolarpv.com

"PV & Grid Power combine if PV energy is insufficient for load."
"

AC CHARGER
AC Charge Current	80A
AC Input Voltage	230VAC
Frequency Range	50/60HZ

"

A simple UPS function can be implemented with a relay - either pass grid through to load, or disconnect from grid and use inverter.
Much more difficult is to combine PV and Grid on AC side, requires synchronized AC waveform and protection against backfeed to grid. Grid-tie hybrid inverters to this.
To accomplish the function more simply, a separate battery charger can be used, an "on-line UPS" or "double-conversion". AC is converted to DC, then DC to AC.

That still shouldn't explain 460W consumption, but possibly the battery charger is using significant inductance of a transformer to block AC current. 80A at 50V = 4000W. 2A at 230V = 460W, 11% of full-load current.

No-load current of a transformer is a thing. Some references say should be under 5%.
Probably more cheaply built and undersized will allow more.

https://cr4.globalspec.com/thread/106496/High-No-Load-Current-on-Transformers

I'm presently delving into transformer core characteristics, and there is a LOT of science and engineering detail in there. After metal is worked into the shape desired, it has to be annealed to restore desirable characteristics. This can be done without magnetic field, or with field in longitudinal or transverse direction. Those produce considerable differences in behavior, good for various applications. Power transformers are just one of many.

Likely, most of that 2A and 460VA is reactive power, not real power. But if your utility meter doesn't distinguish, that doesn't do you any good. (It also means you wouldn't be able to spin the meter backwards like we do with grid interactive inverters for net metering.)

I ran a test of a transformer type battery charger.
On 10A (12V) setting, it draws 0.00A at 120Vrms.
On 55A (12V) "start" setting, it hums moderately loudly and draws 1.18A at 120 Vrms.
That's zero W delivered on 660W setting, 142VA reactive power drawn, 21% of full-load current.

I suspect the GroWatt has a cheap undersized transformer for the battery charger (not a high frequency switcher, and not a larger heavier transformer.) At 50 Hz vs. 60 Hz the transformer goes further into saturation, also at 240V vs. 220V.



If this is what's going on, maybe best to resell it to someone who would only use it for solar, or downstream of their generator. They can run the generator briefly for larger loads, then turn off and run smaller loads from battery.

Alternatively, disconnect from grid, and get a different battery charger without such no-load draw. But it must properly regulate for the batteries you're using, either regulated voltage or have a "maintain" function that is OK to leave plugged in continuously.

 

[Hedges]

It may be your GroWatt will start behaving acceptably once you connect batteries.

I tried putting the 55A starter/charger on a 12V battery. It delivered about 16A, probably around 15V. AC draw increased to 3A.
Probably little change in the undesired "reactive" power, still drawing excess current from grid.

But, if your GroWatt disconnects AC input when battery sufficiently charged, that could stop the waste, except when grid is needed to supplement power for loads.

The "batteryless" feature is probably best for PV daytime use, without grid. If used with grid it has that reactive draw, which would be tolerable for customers whos meter actually measures watts rather than volts x amps.

 

[timselectric]

Thank you man for the info, i rechecked today you sing a multimeter in series with the input.
Solar input is off
Ac output breaker turned off
No batteries installed yet
AC input breaker is on, and still i get 2 amps.
Could you please try it my way, turn everything off including batteries and check the AC input current?
I really appreciate your help

Yes, I'm getting the same as you. I cycled through all modes. With solar, battery, and load, disconnected.
Anywhere from 2 to 2.6 amps , on grid input at idle.
It appears that the inverter is using power to monitor all inputs, whether or not they are connected to anything.
At least, this is my best guess.

@Hedges
When charging or discharging, I could read Anywhere from 3 to 4 AC amps on battery cable. No AC volts, of course. And, the DC current level doesn't affect the AC current level. So, it's just a flat ripple from the inverter.

 

[Hedges]

Any modes available where GroWatt only connects to grid if battery is low (and draws that undesired current), but then disconnects once battery is reasonably fully charged? That should avoid this waste much of the time. So long as it remains disconnected at night unless battery gets too low.

 

[timselectric]

Any modes available where GroWatt only connects to grid if battery is low (and draws that undesired current), but then disconnects once battery is reasonably fully charged?

Yes
SBU and SOL.
Both disconnect from grid, until needed.
But, both require a battery connected.

 

[Joe Samra]

Tim is using an AC/DC clamp ammeter (hall effect), can read DC current.

Joe has an AC only clamp ammeter (current transformer)

Possibly, "No batteries" has something to do with undesired behavior. Can you connect a batch of car batteries?
Then observe any difference in AC current, and read battery current with the AC scale you have (reads AC ripple but not DC.)

Tim - besides AC current in AC grid connection as requested, check AC current in battery cable (with and without grid connected).
I would expect that to be low under no load, but who knows. Likely has ripple when charging.
I find that when driving a large AC load from batteries, although battery DC (average) current matches load wattage, there is a large AC ripple. Capacitors can't buffer 60 Hz, only the higher frequencies of switcher. At least with my low-frequency inverter.

Joe - does your friend also have batteryless setup?
Without AC input, just PV, at least average current has to come from PV panels. Possibly peak current at top of sine wave. But I would guess a high frequency inverter would draw down capacitors to deliver peak current, at least in the batteryless case.

But I still don't know where 2A would be going. That's too much current draw on AC input when there isn't that much current on AC output.

This one?

Customized Solar Power System,Growatt Hybrid System,Split Phase PV System - Swtsolarpv.com

China supplier of solar system - off grid solar system,lithium battery storage system,solar power station offered by Sweet Power. Any questions,pls do not hesitate to contact us!

www.swtsolarpv.com

"PV & Grid Power combine if PV energy is insufficient for load."
"

AC CHARGER
AC Charge Current	80A
AC Input Voltage	230VAC
Frequency Range	50/60HZ

"

A simple UPS function can be implemented with a relay - either pass grid through to load, or disconnect from grid and use inverter.
Much more difficult is to combine PV and Grid on AC side, requires synchronized AC waveform and protection against backfeed to grid. Grid-tie hybrid inverters to this.
To accomplish the function more simply, a separate battery charger can be used, an "on-line UPS" or "double-conversion". AC is converted to DC, then DC to AC.

That still shouldn't explain 460W consumption, but possibly the battery charger is using significant inductance of a transformer to block AC current. 80A at 50V = 4000W. 2A at 230V = 460W, 11% of full-load current.

No-load current of a transformer is a thing. Some references say should be under 5%.
Probably more cheaply built and undersized will allow more.

https://cr4.globalspec.com/thread/106496/High-No-Load-Current-on-Transformers

I'm presently delving into transformer core characteristics, and there is a LOT of science and engineering detail in there. After metal is worked into the shape desired, it has to be annealed to restore desirable characteristics. This can be done without magnetic field, or with field in longitudinal or transverse direction. Those produce considerable differences in behavior, good for various applications. Power transformers are just one of many.

Likely, most of that 2A and 460VA is reactive power, not real power. But if your utility meter doesn't distinguish, that doesn't do you any good. (It also means you wouldn't be able to spin the meter backwards like we do with grid interactive inverters for net metering.)

I ran a test of a transformer type battery charger.
On 10A (12V) setting, it draws 0.00A at 120Vrms.
On 55A (12V) "start" setting, it hums moderately loudly and draws 1.18A at 120 Vrms.
That's zero W delivered on 660W setting, 142VA reactive power drawn, 21% of full-load current.

I suspect the GroWatt has a cheap undersized transformer for the battery charger (not a high frequency switcher, and not a larger heavier transformer.) At 50 Hz vs. 60 Hz the transformer goes further into saturation, also at 240V vs. 220V.

View attachment 92402 View attachment 92403

If this is what's going on, maybe best to resell it to someone who would only use it for solar, or downstream of their generator. They can run the generator briefly for larger loads, then turn off and run smaller loads from battery.

Alternatively, disconnect from grid, and get a different battery charger without such no-load draw. But it must properly regulate for the batteries you're using, either regulated voltage or have a "maintain" function that is OK to leave plugged in continuously.

Hello Hedges, my friend has 4 Amaron batteries installed in his system, he conducted the test i required with batteries breaker turned off and AC output breaker too.
I installed in my panel a modular AC contactor to pass through AC grid to my house without passing by the inverter, i guess it is a normal behavior for growatt to withdraw 2 amps from grid without batteries since @timselectric , me and my friend had the same results, im going to wait for my batteries to arrive, until then i only use the inverter for small loads when needed (not the refrigerator because upon starting its surge is way strong for 4 x 655W panels to handle so the inverter trips and indicates PV power insufficient).
Thank you so much for your help, i really appreciate it.

 

[Joe Samra]

Yes, I'm getting the same as you. I cycled through all modes. With solar, battery, and load, disconnected.
Anywhere from 2 to 2.6 amps , on grid input at idle.
It appears that the inverter is using power to monitor all inputs, whether or not they are connected to anything.
At least, this is my best guess.

@Hedges
When charging or discharging, I could read Anywhere from 3 to 4 AC amps on battery cable. No AC volts, of course. And, the DC current level doesn't affect the AC current level. So, it's just a flat ripple from the inverter.

Thank you man, i guess the best option is to have batteries installed, PV and grid power without batteries did cost me a big electric bill, thanks again.

 

[Hedges]

Thank you man, i guess the best option is to have batteries installed, PV and grid power without batteries did cost me a big electric bill, thanks again.

I think so. Still not optimum for nighttime use, because it will cycle batteries and then connect to grid if low. You might do better adding an automatic transfer switch downstream from GroWatt so if grid is up at night, loads draw from grid. During the day, loads powered by PV supplemented by AC through GroWatt's battery charger.

Selling it and getting one that operates more efficiently might be better.

For PV without batteries, best arrangement is net metering, backfeeding all power harvested into your house wiring, and into the grid if your loads are less. That only works if utility allows this and credits you for spinning meter backwards. I think your present meter spins meter forwards regardless of whether you d draw power or deliver power (based on it spinning forward for "reactive" power which is 50% draw, 50% deliver.)

Next best is zero export. A current transformer around utility feed measures current (and phase, draw vs. deliver, is determined by also monitoring voltage.) The zero-export inverter ramps production up and down to deliver up to 100% of available solar or total consumed by house, whichever is less, without exporting to grid.

Sounds like your GroWatt can be used with batteries to keep power on when grid goes down. And, to recharge from generator if you run that, allowing you to turn off generator sooner and keep running from inverter. Needs to be configured so grid input is disconnected from inverter (hopefully internally) so the 2A draw stops when battery is full. And remains disconnected until battery gets low, so you don't have that draw all night. Batteries should supply starting surge for motors.

For such use, you need batteries able to cycle many times. Lithium has claimed 2000 to 6000 cycles. Various lead-acid a few hundred. In both cases, I think cost of battery divided by all lifetime use exceeds cost of just buying power from utility grid. Exception being some low-cost recycled or DIY lithium batteries.

My inverter, SMA Sunny Island, doesn't work as an on-line UPS like yours apparently does, separate battery charger and always running inverter. It has a relay inside to connect loads to the grid. It consumes 25W (compare to 460W) for one 6kW inverter. My lead-acid batteries are kept at float voltage day and night when grid is up. If grid goes down, after a brief glitch it disconnects from grid and powers loads from battery. PV can be DC coupled to battery with separate SCC, but mine has PV AC coupled with grid-tie PV inverters. If grid is up they backfeed (I have net metering). If grid goes down, they feed my loads and the battery inverter which charges battery or draws from battery depending on AC power draw.

There should be some low-cost grid-tied inverters with zero export. They use a high frequency switcher to convert AC to battery or battery to AC without that large (transformer?) current draw of the GroWatt. Optimal configuration provides battery/PV backup to critical loads, and delivers up to 100% of PV backfed to other loads in the house.

 

[GLC]

I have 1 -4000 watt 110 inverter that uses 6 watts at idle and I have 1- 6000 watt 110/220 inverter that uses 45 watts at idle.

 

[skylink]

Thank you man, i guess the best option is to have batteries installed, PV and grid power without batteries did cost me a big electric bill, thanks again.

Hi, You may see 2amps or so but that is apparent power, https://www.allaboutcircuits.com/te...ent/chpt-11/true-reactive-and-apparent-power/ However the true power used is around 60w really very little,

 

[fblevins1]

I think at the end of the day, the best way to limit how much your inverter cost to just sit there with the lights on is to be realistic about your average load on any given day. If you know you average about 500 watts of load, then a 1 KW inverter is just fine and will consume less than a super whammadyne 5 KW inverter with bells and whistles.

As information, I just did a test of the inverter decent load versus almost no load:

Inverter:
250W load (confirmed thru measurement) = net of 29W for Inverter itself
2W load just charging a wireless speaker = 21W " "

Thanks for all the help. I want to put in an automatic switch DC to AC grid when the batteries get too low... so I'll have to add some kind of alert on that trigger so I can put in a DC switch to turn off the inverter.

Thanks too everyone who responded. Best forum. Saved a huge amount of time and grief with your expertise previous on cheap Chinese DC breaker issue.

The ATS that I use, quietly does it's job without any bells or whistles. When the batteries drop below 12.3 volts it switches over to grid, but empirically the inverter doesn't seem to kill off the battery at night. I think the reason for that is under load (say....200 watts) when the battery hits 12.3 it switches over to grid but then the load is reduced on the battery and it's voltage creeps back up to around 12.5 volts even with inverter on, giving you enough juice to power to inverter for the rest of the night without fear of your DOD going below 12.3 volts (or whatever the lower limit is for the battery and voltage system you use. Get the ATS first, wire it in and then just watch what your battery does and you may find you don't need to worry about inverter killing off your battery once the grid kicks in and your load is reduced, but then again...if you are good at wiring in switches then hell...go for it, sounds like fun.