Inverter Self-Power consumption / efficiency

[half.price]

Hi all

Not sure, if this question has been posted already, but I do face a serious situation, making full setup questionable

I do have an H3 Foxx inverter, 6,5 kWp Solar and 8,5 kWh battery setup.

Inverter is described with 95% or more efficiency, but real data do show something very different.
Please check this examples:


Inverter does consume minimum 150 Watt and up to 300 Watt, depending situation

Ok over day with sunny weather. PV does give for example 4kWp, battery 100%, inverter output 3,8kWp. Loss of 200-300 Watt.
Strange at night. PV zero input, battery first discharging, house demanding (inverter outout) at 300 watt, but battery discharging with 500 Watt. So inverter using 200 Watt

And even stranger!!!!
At night, battery empty (at 10%), house usage 300 Watt BUT inverter still consuming 150 Watt!!! So grid consumption is at 450 Watt!!!

Why the hell??
This is far away from calling it 95% efficiency at all, as inverter itself does empty my battery over night

Is this as designed?

Any idea? Any input? Any setting I can take?
I would assume, inverter should go to Standby, using 5 watt, if battery is empty and PV does not bring anything.

[calum]

https://github.com/nathanmarlor/foxess_ ... ssions/419

Short version: yes, it's your inverter, no there isn't much you can do about it.

[m15k]

This is really annoying. It seems to depend also on the battery size. At night: 0 Solar, 10% SOC, my FoxEss draws 330W...

[alistair.miller]

I am not sure if this will help but it could be worth making sure your system is using the latest versions.

I found our system using around 90 watts but since getting an update a few months ago the usage is more like 27watts.

[m15k]

I am not sure if this will help but it could be worth making sure your system is using the latest versions.

I found our system using around 90 watts but since getting an update a few months ago the usage is more like 27watts.

Can you post your firmware versions? Can the firmware be updated manually?

I'm running on:

Master Version: 1.83
Slave Version: 1.02
Manager Version: 1.43

[alistair.miller]

Ours is a h1 inverter so I'm not sure versions will be of much help, versions being:

Master Version 1.63
Slave Version 1.02
Manager Version 1.68

But the updates have helped so it's possible any newer update may also improve your system.

There are a few on here with a vast amount of knowledge who can offer more advice than I could ever do.

Updates for us, we have to ask FoxESS support each time although the preference is your installer keeps you updated. I don't think there is a way for end users to do it.

[m15k]

I wonder what the inverter is doing with that amount of power. From my knowledge it started to draw that much power when the batteries were installed.

[alistair.miller]

When we started off with an 8kw battery system it always seemed our system used around 40watts extra an hour for a house load of 200 watts or less. When we took the battery size to 28kw this jumped to over 90 watts extra being used.

We downsized to 20kw and that number changed to around 50 watts. Since an update or two ago this now seems to be around 20 - 30 watts so for the h1 and cubes they seemed to have improved the system.

I remember a FoxESS tech support mentioning some of the usage / loss will be down to the inverter matching the battery valts to the mains valts. Although some of what was said went over my head.

We have a family member with the same set up but they have a 16kw battery which works out at 240 volts and they seem to use / loose much less than we do, with ours being around 300 volts and our mains being around 243 volts so I guess some of what he said must be true.

Temperature and the amount of power being converted from dc to ac changes the amount it uses of course which can result in a few 100 watts being lost when converting several kws.

We only use the fox app which isn't 100% correct in the data it shows so I take it as a guide only. It never matches our smart meter.

[calum]

The inverter has to keep the necessary power electronics ready to provide multiple kilowatts of AC power at a literal moments notice. Think about if you turn on the oven, or boil a kettle, or turn on a hairdryer, or possible several of these things at once. Doing that is not 'free', energetically speaking; there are some inefficiencies, and those inefficiencies are greatest, proportionally, at low loads.

Certainly the firmware that controls the power electronics can be made more efficient, and this is a good reason to keep up with firmware versions from Fox, there have been very noticeable efficiency gains vs the earliest firmware versions. But there are also limits to those improvements, as you approach the limits that the physical electronics are capable of.

As an aside, the Foxess app / website can never be very accurate, as it only samples what's going on every five minutes to give you an idea of what is going on with power flow between the various components. If you want more accurate readings and data, you need to connect to the modbus interface of the inverter with NodeRed, Home Assistant or whatever.

[tommyhechtel]

Hello.
I understand the inverter needs a certain energy consumption of 200W or more for AC/DC transformation and to be ready to provide instantly a high amount of energy from PV or battery.

What I do not understand is why the inverter also uses 200W with battery on min SOC and no PV input (at night).
I would think then the inverter goes to "cold standby" and just uses about 15W while the complete load is directly taken from grid without any need for AC/DC transformation or charge/discharge of battery.

In winter times with 16h without PV input and empty battery this means a difference of 3 kWh every night.

[calum]

Hello.
I understand the inverter needs a certain energy consumption of 200W or more for AC/DC transformation and to be ready to provide instantly a high amount of energy from PV or battery.

What I do not understand is why the inverter also uses 200W with battery on min SOC and no PV input (at night).
I would think then the inverter goes to "cold standby" and just uses about 15W while the complete load is directly taken from grid without any need for AC/DC transformation or charge/discharge of battery.

In winter times with 16h without PV input and empty battery this means a difference of 3 kWh every night.

The thing is, the system doesn't "know" where it is, or when the sun will come up, or any of that - it is engineered to be ready at all times, in case needed.

I imagine it would be possible to have a low power mode that would wake up the main power circuits when they are needed, to deal with the circumstances you describe - particularly if the system had a way to know when to expect sunrise and sunset. Presumably the cost increase, in both hardware and engineering, is prohibitive in a very competitive and price-sensitive market.

Unfortunately this is the hidden price for home solar and batteries - they are always using a bit of power in the background.

[tommyhechtel]

I am not a specialist on electronics or software at all, but is this really so much impacting the hardware solution?
Couldn't this be solved by software logic, maybe similar to

In case Battery state at min SOC and:
1. PV input < x V for > 10 min => System standby (inverter inactive, no interaction with battery, "cold" standby consumption)
2. PV input > x V for > 10 s => System wakeup (inverter active, interaction with battery, "warm" standby consumption)

Instead of PV voltage level also the sunrise and sunset time based on location could be used in combination with SOC to determine cold standby phases. Or just let the user input those information in the app.

Don't get me wrong, probably this is not possible for certain reasons. If it would be so easy for sure it would be implemented already from the beginning.
I just try to get a better understanding of the "standby" power consumption when all loads are 100% covered by grid.

In my case it looks like the battery is constantly charged and discharged 1-2% over min SOC at night since firmware update (1.69/1.03/1.87).
So "expensive" grid energy is used to charge battery just to push most of it back to grid then for almost no money. And this of course + 200 W inverter consumption.
For sure not a very big commercial impact, but not really following my expectations about the high efficiency that is promised for FOX ESS inverters.

Ticket is raised and closed already with the feedback that next update should improve the situation. Fingers crossed

[v1lad]

HI All !
I faced the same situation after this morning's update. My inverter is now consistently drawing 150W from the grid at night with the battery at minimum ( 10% ).
Update was from 1.56 to 1.71.

I have found solution: Factory Reset, after you need just set up safety standard / country code and date / time.
The consumption dropped from 150W to 7W.

P.S. I got happy too early. In the morning, the problem returned. The inverter started consuming 150W again.

P.P.S Support made downgrade for me
Master : 1.69
Slave: 1.03
Management : 1.71
And seems the reason was downgrade Master from 1.90 to 1.69.

after the downgrade, the inverter consumption dropped from 150W to 40W in active mode.

[PhilCamb]

Hi All,
I have just had a new installation and noticed the 'discrepancy' between the numbers shown on the app suggesting the inverter was consuming a significant amount of power. After reporting it to Solar Power they agreed to send out an engineer to check everything over. For the rest of the day I monitored the energy flow diagram closely on my PC and, using screenshots, recorded what it showed periodically throughout the day, From what I could see...

1 - When the Panels were producing relatively low amounts of power, the 'missing' power was significant (up to 260W).
2 - When the Panels were producing significant amounts of power (over a Kw), the 'missing' power drops significantly and went as low as 10W.
3 - When the Panels were producing no energy (eg at night), the 'missing' energy dropped to virtually zero.

The engineer came a couple of days later and could not find any faults but took pictures of my recordings to report to Fox. They thought it could be to do with the way the inverter calculates power from the panels when they are at lower levels and maybe it could be power loss in the cables from the panels to the inverter. My runs are maybe 20m but they suggested that was not unusually long.

They rang Fox and spoke to someone there who said this had been reported by quite a few others and suggested a software upgrade. After the upgrade the numbers on the energy flow all added up to within a watt or two across all devices so problem fixed. But....

The revised numbers on the energy flow map, showed lower output from the panels. This suggests the discrepancy was due to how the inverter calculates the panel power output. I would have loved it if the change resulted in additional power going to the house or battery but at least, I can get a more reliable picture of what is really happening.

Hope this helps anyone with the same problem.

[Dave Foster]

Hi All,
They rang Fox and spoke to someone there who said this had been reported by quite a few others and suggested a software upgrade. After the upgrade the numbers on the energy flow all added up to within a watt or two across all devices so problem fixed. But....

The revised numbers on the energy flow map, showed lower output from the panels. This suggests the discrepancy was due to how the inverter calculates the panel power output. I would have loved it if the change resulted in additional power going to the house or battery but at least, I can get a more reliable picture of what is really happening.

Hope this helps anyone with the same problem.

Yes i've heard this a few times recently and that an upgrade to latest firmware corrects the misreading.

I'd recommend you take a look at this that one my colleagues has produced - very helpful in showing how it works and where / what scale of losses you might anticipate within the system https://github.com/TonyM1958/HA-FoxESS- ... it-work%3F

[RoyS]

This is really annoying. It seems to depend also on the battery size. At night: 0 Solar, 10% SOC, my FoxEss draws 330W...

How did you work out the amount drawn from inverter please? My electricity consumption has increased from 5-8kwh to over 10kwh once the Fox inverter was installed. It defeats the purpose of saving energy. Any help is much appreciated. Thank you.

[Dave Foster]

This is really annoying. It seems to depend also on the battery size. At night: 0 Solar, 10% SOC, my FoxEss draws 330W...

How did you work out the amount drawn from inverter please? My electricity consumption has increased from 5-8kwh to over 10kwh once the Fox inverter was installed. It defeats the purpose of saving energy. Any help is much appreciated. Thank you.

Do you have the V2 app as you should be able to work it out from there - naturally the winter months are the worst as you have very little solar and the overheads of maintaining the system, 1-2kW is probably not unexpected but any higher needs thinking through.

If you open the V2 app and swipe right, you will get to this page - choose month and pick a full month

That is mine for November (I am quite a heavy power user), if you lift the main statistics out you get to these calculations -

Your solar Production was 91.2 kWh (A)
You Exported 23.2 kWh (B)
So your Self-Consumption is (A-B) = 68.0 kWh (C)
Your Self-Consumption ration is (C / A) = 75%

Your consumption was 641.8 kWh (D)
You Purchased 643.4 kWh from grid (E)
Your Self-sufficiency is (D-E)=-1.6 kWh (F)
Your % self-sufficiency is the ration between (F / D) =0%

Your system efficiency (Input/Output) is:
Input = Production (A) + Purchase (E) i.e. 91.2 + 643.4 = 734.6kWh
Output = Export (B) + Consumption (D) i.e. 23.2 + 641.8 = 665.0kWh

Your system losses is the difference between Input and Output (69.6kWh ) which is 9.5% of the Input ~ 90.5% efficient.

If you post a few pictures of your stats (pick as many full months as you have), I have a spreadsheet I can drop the numbers in and it will do the calcs for you - or just post the main numbers from there i.e. Production, Export, Consumption and Grid Purchase for each month.

[RoyS]

Hello Dave,
Thank you so much. You took your valuable time to answer me in so much details.
Here's my December production, tiny compared to you. I would like to find how much energy the inverter use per day if possible.
Thank you

[Dave Foster]

Hello Dave,
Thank you so much. You took your valuable time to answer me in so much details.
Here's my December production, tiny compared to you. I would like to find how much energy the inverter use per day if possible.
Thank you

That's a little unusual as when I run the figures your system is more than 100% efficient which is not possible unless something was measured wrong in the month - do you have any other sources of generation, another solar inverter ?

This is what I got -

Your solar Production was 11.5 kWh (A)
You Exported 3.1 kWh (B)
So your Self-Consumption is (A-B) = 8.4 kWh (C)
Your Self-Consumption ration is (C / A) = 73%

Your consumption was 333.3 kWh (D)
You Purchased 299.6 kWh from grid (E)
Your Self-sufficiency is (D-E)=33.7 kWh (F)
Your % self-sufficiency is the ration between (F / D) =10%

Your system efficiency (Input/Output) is:
Input = Production (A) + Purchase (E) i.e. 11.5 + 299.6 = 311.1kWh
Output = Export (B) + Consumption (D) i.e. 3.1 + 333.3 = 336.4kWh

Your system losses is the difference between Input and Output (-25.3kWh ) which is -8.1% of the Input ~ 108.1% efficient.

Either you have more generation than is being shown here or there is something wrong in the grid purchase or consumption measurements - probably best to start with can you confirm how much electricity you have used on your December bill as we should be able to trust the smart meter.

[RoyS]

Sorry, I did not realise it. Yes, I have a solar edge system. Production for December 24 is 68.17 kWh.
Thank you

[Dave Foster]

Sorry, I did not realise it. Yes, I have a solar edge system. Production for December 24 is 68.17 kWh.
Thank you

ok, thanks - if I assume all of that is production then the new figures are

Your solar Production was 79.7 kWh (A)
You Exported 3.1 kWh (B)
So your Self-Consumption is (A-B) = 76.6 kWh (C)
Your Self-Consumption ration is (C / A) = 96%

Your consumption was 333.3 kWh (D)
You Purchased 299.6 kWh from grid (E)
Your Self-sufficiency is (D-E)=33.7 kWh (F)
Your % self-sufficiency is the ration between (F / D) =10%

Your system efficiency (Input/Output) is:
Input = Production (A) + Purchase (E) i.e. 79.7 + 299.6 = 379.3kWh
Output = Export (B) + Consumption (D) i.e. 3.1 + 333.3 = 336.4kWh

Your system losses is the difference between Input and Output (42.9kWh ) which is 11.3% of the Input ~ 88.7% efficient.

So efficiency is good at 88.7% (90% would be ideal) and your losses is 42.9kWh ~ approx 1.38kW per day in December which is about right.

There are a number of stages where losses occur, in producing the solar (MPPT), and converting to and from ac to dc, plus storing power in the battery and recovering it later (I assume about ~10 to 15% round trip) so if you are charging your batteries you will lose approx 10% of whatever you put in to get it out again.

[RoyS]

Thank you so much.
I believe I lost ~1.38Kwh per day in December.
Thank you so much!

[ddixon]

I see something similar, and think the recorded battery discharge rate is off:

KH7 (Master : 1.41, Slave : 1.01, Manager : 1.40)
EP11 (Master: 1.005)

Stats either via the inverter screen or via modbus are inconsistent:
Battery charge total: 200 kWh
Battery discharge total: 310 kWh (but this should be at most the charge total + 10 kWh)

Looking at a single representative day, where the SoC started at 73% (of 10.36 kWh), fell to 49% then charged to 100% then fell back to 71%:
total reported charge = 5.8 kWh - OK (nominal increase in charge = 5.3 kWh)
total reported discharge = 9.2 kWh - far too high (nominal decrease in charge = 5.5 kWh).
Looking at the house load vs. discharge power, the discharge power is around 200 W higher than the load for the ~17 h where the battery is being used (overnight: 150 W load; 350 W discharge), which accounts for the difference of 3.4 kWh between charge and discharge amounts. There is no net import/export during this time.
My most likely explanation is that the reported discharge rate is 200 W higher than the actual rate.

Interestingly, the Fox cloud web view looks to show more sensible numbers for discharge rate, although its charge & discharge daily total are still skewed, so perhaps the discharge power values have been adjusted behind the scenes.

So - a bug/inaccuracy in the reported battery discharge output?

[M.U.]

There is probably no error:
To serve a load of 150W the inverter draws 350W from the battery. The difference of 200W is the power consumption of the inverter itself.
So the math is correct. It‘s the pretty high power consumption that makes the difference. (at least for my H3-8.0).
So you draw more power from the battery for the inverter itself than you need for your load … and the resulting efficiency is pretty poor for the time where your load is quite low (so….for the whole night…).

[ddixon]

There is probably no error:
To serve a load of 150W the inverter draws 350W from the battery. The difference of 200W is the power consumption of the inverter itself.
So the math is correct. It‘s the pretty high power consumption that makes the difference. (at least for my H3-8.0).
So you draw more power from the battery for the inverter itself than you need for your load … and the resulting efficiency is pretty poor for the time where your load is quite low (so….for the whole night…).

That's what I thought at first but I can't get 310 kWh out from a battery I've only put 200 kWh into. The battery discharge rate based in drop in SoC looks fine - but the reported power output does not. I'm not particularly bothered as the system is working fine in practice - but it would be nice if the numbers made sense.