Fox Cloud 2.0

[Linton]

I have struggled to work out the precise meanings of the terms 'Self-consumption', 'Consumption' and 'Self-sufficiency' as used on the second page of the new FoxCloud App. This is what I think they mean. If anyone knows differently, please enlighten me.

1. 'Production' (P) is the total energy output in the given time interval from the PV panels.
2. 'Export' (E) is, obviously, the total energy exported to the grid.
3. 'Self-consumption' (SC) is therefore the total energy generated by the panels which is consumed on site.

4. 'Consumption' (C) is the total amount of energy used to power your TV, lights, washing machine etc in the house.
It is made up of two parts:
5. 'Import' (I) which is, obviously, the amount of energy imported from the grid, and
6. 'Self-sufficiency' (SS) which is the amount of useful energy delivered to the house from the inverter/battery system

As an example, my lifetime figures are currently as follows:
Production = 10.5, Export = 5.3 and Self-consumption = 5.2 MWh
Consumption = 5.6, Import = 1.8 and Self-sufficiency = 3.8 Mwh

Much of the confusion arises from the fact that the figures for 'Self-consumption' and 'Consumption' are often very similar and some members have wondered why they are not the same. The fact is, these two figure have no relation to one another. The interesting comparison is between 'Self-consumption' and 'Self-sufficiency'. The difference between these two is equal to the total amount of energy lost in the conversion processes inside the inverter and battery.

In my case this figure amounts to 5.2 - 3.8 = 1.4 MWh which works out at an average rate of 70W. Not much more than an old-fashioned light bulb.

Another interesting figure which you can calculate is to divide this figure by the total production (P) and express it as a percentage: 1.4/10.5 x 100 = 13%. This is the percentage of the total energy produced by the panels which is wasted as heat. The overall efficiency of my system has therefore been 87% which I regard as pretty remarkable. (Note that if you do this calculation over a short time period such as a day you will only get reliable results if the battery is in the same state at both ends of the time period.)

One last point. Although the figures for the lifetime usage appear accurate, the daily and monthly figures before February 2024 are incorrect. I do not know if FoxESS plans to update the database which FoxCloud 2.0 uses.

I hope this information is correct and useful. It would have saved me a lot of mental effort if Fox had issued a simple guide themselves explaining all this.

Oliver Linton

[Dave Foster]

I’ve copied a link from a colleagues page, he has produced some excellent guides that will hopefully help, this is the one for the V2 app https://github.com/TonyM1958/FoxESS-Cl ... Fox-App-v2

[Linton]

Thanks for this very useful link. I am pleased to say that it confirms my interpretation of the quantities.

I could, however, point out that the method of calculating the losses (P + IM) - (C + EX) is algebraically equivalent to (SC - SS) and the latter calculation is easier. Also in calculating the efficiency of the system the denominator should really only include the output from the panels (P), not (P + IM). The reason for this is that energy from the grid does not actually pass through the inverter, it is used directly with 100% efficiency. If you had a system which used lots of energy from the grid but only a small amount from the solar panels, then the calculated efficiency could approach 100% - an absurdity.

Oliver Linton

[Dave Foster]

The problem with the grid energy is that it doesn't always pass through the inverter unscathed, a lot of people on low tariffs will use it to charge the batteries, so there is a loss in the ac>dc conversion, and in the battery chemistry - then when recovered it will have a loss in the dc>ac conversion back again.