FoxESS Community - Owners & Installers Forum

Hi,

I have been advises by Dave here in the forum to set the Compensation Bias to 80W as the system is still pulling off the grid at night when there is a full battery.

Would anyone know how this can be set and where or does the installer have to do it as he has no idea where to look.

Thanks in advance

It is an installer option and not available via the menus (you must also have the latest firmware), contact your installer and ask them to set it for you, or if you have problems email Fox support with your inverter serial number and ask them to set it for you.

Thanks Dave, The installer doesn't know how to set it but they pushed my firmware update to Fox to do. Bit worrying? as they should be doing it right? I will ask FOX to set it. Is it possible to view what the BIAS is set to currently to make sure know when the correct value is set? Is it in the settings to view anywhere?

Keen to get it sorted, the system has generated over 1.6Mwh in last 3.5 weeks so its good to know the system will be set correctly and not drawing off the grid at night. If the 80W setting doesn't change much, is there anything else to set or check why the house is drawing off the grid at night when there is a 14KW battery to cover the house usage?

This is the example I'm looking at for why the house is using electricity at night. Doesn't seem right to me if I have a decent battery and minimal load at night. Always pulling from the grid. Top image is a typical DAY, the bottom one is the week view.

That looks pretty normal in Self use mode, no grid use during the day when the sun is up and the bias automatically shifts towards export, and overnight when the bias shifts the other way there is a small usage.

You would expect your installer to know how to do it, the larger installers that work closely with Fox would but for installers that use a variety of equipment it's probably a bit much to stay on top of every feature and this is quite a new feature.

Sadly there is no way of telling what it has been set to unless your are an installer, nothing in the settings or in the app - so once set the only obvious way to tell is the very small overnight grid use should reduce fairly close to zero.

Thanks Dave,

I'll follow up with the installer, failing that I'll ask FOX to do the change. Is 80W the recommend value then? I'm still very unclear why near 2kWh is used over night for a fridge and small derives on like internet and Wi-Fi router etc. I invested in a large battery to be able to have next to ZERO draw off the grid other than the sync with the grid at most. Why is 2kWh used I do not understand, thinking that the whole idea was to be as off grid as possible and reduce as much dependency from the grid as possible. If the bias is set to 80w, do you think this is the ideal value or is there any point in putting a higher or lower value here....what makes 80W the best value for the Bias - keen to learn more.

If you look at your first octopus graph of grid usage overnight, you are trying to find an average bias point that would overcome the hourly usage - in that graph if you draw a line across at 0.08kwh (80 watts) you would have the vast majority of the import peaks below that line.

You might want to start a little bit smaller at say 60 watts which would cover much of the import as you will probably never achieve absolute zero (but if you are getting Fox to do it for you best to start at 80 watts and monitor for a few weeks).

The reason for this is that with any grid tied inverter when larger appliances such as fridges turn on /off (particularly the larger American fridges) the load is instantly there and whilst it may only take several hundred watts the inverter has to firstly measure the load change and then balance the load from batteries, it takes the inverter a small amount of time (seconds) and in that small window of time the grid will be filling in until the load has balanced. Likewise when the load turns off the battery will be still supplying power and again for a few seconds that will be sent to export until the inverter adapts to the new balance - this is what creates the usage (and export) you see overnight.

When you set the bias to 80 watts the first 80 watts of any instant load will always be taken from battery making the grid demand much smaller, as I said there will always be some demand but if you can get it down to 0.5kWh in a day you will be doing well.

Just to add, as an alternative test that will help - change your workmode to Feed-in First overnight and then back to Self-Use in the morning, whilst that may seem a little counter intuitive feed-in first changes the bias slightly towards export and so your overnight usage should drop - perhaps as much as half of what you are seeing.

Thank you Dave,

That's a really good and clear explanation and really helps. I will leave it with the installer for now, if they don't reply end of the week I'll ask FOX to do this for me. 80w is a good number as you say, I'm generating around 55-65kWh per day for export as I use very little day to day. At most it was 6kWh given my low usage.

Will mentioned that the new firmware in his Jan 2025 video was initially for the K series, has it been rolled out to the H3 series yet?

I have just been told by my installer that the Compensation Bias option is not available for the H Series yet. Do we have any ideas on how often FOX role out updates from the K series to the H Series so this feature will be possible?

merango wrote: ↑Wed May 07, 2025 11:29 am I have just been told by my installer that the Compensation Bias option is not available for the H Series yet. Do we have any ideas on how often FOX role out updates from the K series to the H Series so this feature will be possible?

It’s definitely on the KH, H3 and H1 (Gen 2), it’s possible it hasn’t yet made it to the H3 Pro but with that being at the premium end of the spectrum you would certainly expect it to - i’ll add this question to the next Fox update session and get confirmation.

Thank you Dave, very kind. If they do have a response, could you ask rough ETA for possible adoption for the H3 Pro. Keen to get that set and tested.

Thanks again.

Hi Dave,

I wanted to give you a quick update on the issue on the Compensation bias we discussed some time ago and waiting for FOX to hopefully support this on the H series.

After a few weeks of testing I'm seeing some very very strange readings.

During a good solar day, the house is powered 100% off the panels, the battery is charged to 100% and the rest is then exported. If the dishwasher or oven is used during the day and there is enough Kw from the panels the system is supplying and still exporting fine.

As the sun goes down the panels still power the house until it gets too low then the grid is used 100% of the time until the following morning. I understand the bias issue but the house has a regular 100-300w load as a constant, not peak or sudden demands, so why is the battery not being used first 100% for this load and the grid 2nd?

So far I have never seen the battery used at all at night, it's all grid import to run the fridge, the NAS, the VCR and a few other devices, all on constant load so why is the inverter not detecting this and using the battery power?

I have done some testing at night and turned the microwave on (900W) and the oven on and the kettle. The app takes a few minutes to update and show the load, but the BATTERY is then used to supply this power. As expected.

I can only assume that the 3 phase 15Kwh inverter is more on the industrial scale and isn't detecting the very small power consumption and not detecting it? Is there anything I can do to adjust the system to actually use the battery at night? I have tested this for over 3 weeks and its always the same 100-300w load and the battery just doesn't kick in at all. LARGE loads yes like the oven, emersion heater etc, but general night time load nothing.

Any suggestions as I'm just importing every night with a 100% full battery doing nothing. Is the 3 phase inverter not sensitive enough to detect the minimal load? Can I change any settings to make it more sensitive and work as I would have expected it to at install?

Thanks

This is not compensation bias but standby load setting.
The problem you have is on a massive 15kW 3ph pro inverter the standby amount is fairly high.
Fox have just added standbyload threshold to the KH and H1-gen2 and it can be set to between 20-200w so will be interesting to see what options come over to the H3 pro in future updates.

Hi Will,

Thanks for this, so I am semi correct that the massive Invertor can't see the small load in essence and therefor ignores it and doesn't trigger the battery to supply the power to the house on a night?

Do you have any rough ETA on the system features being introduced to the H3? Seems odd that the additional software features roll out to just the lower models and the higher end ones have to wait? Don't they test across beta testers on all models?

Assume this setting as you say cannot be changed manually on anything yet on the H3 Pro and I will have to wait for the firmware roll out to introduce this feature?

no timeline. Remember that 3ph inverters are more complex and in normally larger installs, so they are last to be updated. As Fox ships software nearly weekly, it shouldn't be long. I'll ask my fox contact when I next speak with him.

Thanks Will, much appreciated it and happy to be a tester

Will wrote: ↑Tue May 27, 2025 3:43 pm no timeline. Remember that 3ph inverters are more complex and in normally larger installs, so they are last to be updated. As Fox ships software nearly weekly, it shouldn't be long. I'll ask my fox contact when I next speak with him.

Hi Will, hope you are well.

Any update on the new firmware to resolve this issue as I'm still pulling off the grid under 200W and keen to change this sensitivity to allow greater use of the batteries than importing off the grid with a full battery stack.

Morning,

The latest versions available are:

H3_Pro_Master_V1.62
H3_Pro_Manager_V1.34

As soon as I see an update, I'll post on the firmware topic https://foxesscommunity.com/viewforum.php?f=29 and try to update this post.

Hi Will,

Thanks for that, any idea where to check on the firmware of the system on the app or the website log in? Or does it show on the front of the inverter?

My Datalogger is this. Is this up to date?

Hi

Hope you don't mind me posting on this thread. I don't have an installer account so need Fox to make installer setting changes for me.

I have KH10 inverter and 2x EP11 batteries. When not generating sufficient solar and drawing from battery, Octopus reports that the typical grid draw is around 80-90W.

Do I need to change the compensation settings to reduce this figure? On a bad solar day I will draw up to 2kWh from the grid so would like to reduce this if possible...not sure if this is just compensation setting or anything to do with standby load? I am on a single phase system and think installer told me he put the compensation setting as -10.

Any tips/suggestions?

Thank you!

Not a problem, a problem shared and all that.

I'm unable to get that setting yet, waiting for the firmware to allow it on my H3. sucks as I'm pulling 2-3kW per day also and want the batteries to actually kick in to run the 300-500w load in the evening and not pull from the grid.

Keen to get this pushed from Fox.