FoxESS Community - Owners & Installers Forum

Posted: **Tue Nov 04, 2025 9:43 am**

How can I track my inverter power use? I use the Fox Modbus integration in Home Assistant and I'm trying to track down how much of my currently untracked usage is consumed by the inverter

Posted: **Tue Nov 04, 2025 10:15 am**

This can be a complex subject, one of my colleagues has done an excellent how does it work guide here and this cover all of the various possible losses that can occur in the system https://github.com/TonyM1958/HA-FoxESS- ... it-work%3F

If you have modbus this is the template sensor I have written that calculates system losses

Code: Select all

      - name: "System Losses"
        device_class: "power"
        unit_of_measurement: "kW"
        state: >
          {% set sl = ((states('sensor.pv1_power') | float(default=0)
                      + states('sensor.pv2_power') | float(default=0)
                      + states('sensor.grid_consumption') | float(default=0)
                      + states('sensor.battery_discharge') | float(default=0)
                      - states('sensor.battery_charge') | float(default=0)
                      - states('sensor.feed_in') | float(default=0)
                      - states('sensor.load_power')|float(default=0) )) | round(3) %}

and a riemann sum that converts that into energy (kWh)

Code: Select all

  - method: left
    name: losses_sum
    platform: integration
    round: 2
    source: sensor.system_losses
    unit_time: h

Posted: **Tue Nov 04, 2025 3:00 pm**

Thank you! That's great for detecting losses in the system. Is there also a way of detecting how much the inverter itself uses? I assume this number is rolled up in the "Load Power" number, but I'd love to be able to track inverter consumption separately, much like I do with things like my fridge.

Posted: **Tue Nov 04, 2025 4:16 pm**

That’s very difficult to isolate, system losses is the closest you will get to a sum of all losses in the inverter/batteries etc.. but to get to inverter consumption on it’s own not so easy.

When there is no solar it is effectively the difference between the battery discharge power and the load power, but as you could be charging or exporting you need to take into account feedin, grid consumption but that still only gives you the inverter use when it is running as a battery system so by the time you throw PV back into the mix you are at the system losses value.

Posted: **Sun Nov 23, 2025 9:02 pm**

So from my understanding this high power consumption with attached batteries is most likely a bug or could be fixed in software:

* If you turn off your batterie the power cosumtion drops significantly (200W)
* If you change work mode from self-use to backup the power usage drops significantly (200W)

If batterie is at soc and it's night (inverter knows date / time) there's no need to be in hot standby.

But as this topic is already older than a year and new inverters are released I don't see that thiw behaviour will change in future...

Posted: **Sat Dec 20, 2025 6:15 am**

I have a 41.7 kwh battery with H3 10kw Inverter. At night my power consumption is between 230 to 380 watts. 1 600 L fridge freezer combo, 1 x 400 L upright freezer and 1 x 60 L bar fridge.
I can understand your frustration at power draw from a small battery system.

Posted: **Sun Jan 25, 2026 3:21 pm**

Thanks for the tip on how to keep track of the inverter losses. I've just added to my HA Energy section and will help undertanding the "untracked" consumption.

Posted: **Sat Feb 21, 2026 9:11 am**

I am still a learner with all this, but have also noticed a lot of energy going missing which I have assumed is being used by the inverter.

I have a Shelly CT clamp on the tails going into the Consumer Unit which measures the power the house is using in w. My hypothesis is

Inverter Power use in w = ( Load Power reported by the inverter w ) - ( House use reported by the shelly CT w ).

It's complicated by the shelly has a resolution of about 1 second whereas the HA modbus has a resolution of 10s I believe. As the house load can be really choppy some smoothing and massaging of the numbers is required.

I have a template sensor, pwr_inverter_w, which does this simple subtraction but removes outliers ( <0 and >250).

Code: Select all

{% set previousState = this.state | float( 0 ) %}
{% set currentState = 
 ( states( 'sensor.kh7_load_power' ) | float(0) * 1000 - states( 'sensor.shelly_ct_house_load_w' ) | float(0) ) | round(0)  %}
{% if currentState < 0 or currentState > 250 %} 
  {% set currentState = previousState %}
{% endif %}
{{ currentState }}

(I am sure the if can be done on one line but i like to understand what i did months later

)
This produces a pretty picture:

As this is really choppy, I then filter it:

Which on inspection makes a bit of sense, you can see a peak when the invertor is working hard between 16:00 -> 19:00 where we export, and the 01:00 when in winter we import.

I then have a integrating sensor/utility meter which does the conversion to kWh per day.

So you can see our KH7 uses 2.5 to 3kWh per day, which I find quite a lot. I've tried all sort of things to see if I can influence this but none work. In fact if you turn battery and solar off at the switch, the inverter uses a lot more. With the losses in the various other conversions, when the house is quiet overnight and running only on battery, total efficiency is < 50%.

At that poor efficiency, overnight I would probably turn the whole system off and pay the 25p a unit octopus wants, but that isn't possible. I think there should be a software setting that turns the invertor and the whole system into standby mode where it draws only a few watts, similar to how other hardware works, and you can then send a Wake on Lan packet which turns it on.

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