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Negative Revenue
Posted: Thu Jan 29, 2026 9:11 am
by Jimmyrn85
Good morning all, I have a newly installed system on the garage with a Fox H1 G2 5.0kw inverter. 7x 445w panels at the moment but there is plenty of scope for adding more down the line.
I have setup in the app my tariff, which is purchasing lecci from the grid at 0.239pence per kw/h.
For context, I have an existing "rent-a-roof" system which was installed before I purchased this house and the lease has 12 years to run, therefore I cannot be paid for any export I produce, that all goes to the "rent-a-roof" company. I just get to use any lecci I want. I will install a battery on the Fox system at some point.
So with that in mind, why do I get the odd days showing negative revenue? What is that? I would like it to show me for every kw/h produced by the new system that I've saved 23.9pence.
Your advice/thoughts would be appreciated!
Re: Negative Revenue
Posted: Thu Jan 29, 2026 9:24 am
by Will
can you post a screen shot of the energy flow page so I can confirm how your system is setup.
The short version is the inverter will be recording it's generation without any additional action.
Re: Negative Revenue
Posted: Thu Jan 29, 2026 9:38 am
by Jimmyrn85
Hi Will, this page?
So do you mean by that, the negative value could be the cost of just running the inverter on days when there is no sun?
Re: Negative Revenue
Posted: Thu Jan 29, 2026 10:15 am
by MaterialBarracuda48
Not that page, that is your "home" screen.
Swipe right to left, then scroll to bottom to see the energy graph.
Re: Negative Revenue
Posted: Thu Jan 29, 2026 10:29 am
by Jimmyrn85
Thanks, here is a screenshot of the month, and of the 27th day which had a negative revenue of 17pence.
Re: Negative Revenue
Posted: Thu Jan 29, 2026 10:40 am
by MaterialBarracuda48
Jimmyrn85 wrote: ↑Thu Jan 29, 2026 10:29 am
Thanks, here is a screenshot of the month, and of the 27th day which had a negative revenue of 17pence.
You are welcome, I will let Dave or Will respond with better information than I can provide.
Re: Negative Revenue
Posted: Fri Jan 30, 2026 2:46 pm
by WyndStryke
Jimmyrn85 wrote: ↑Thu Jan 29, 2026 9:38 am
So do you mean by that, the negative value could be the cost of just running the inverter on days when there is no sun?
My system has a parasitic loss of about 100W 24/7, so 2.4kWh in a day. That's a KH7 with 15kWh of usable battery in an EC4300 stack. Each system will have a different parasitic loss, based on the number of computers in it, the firmware versions, etc.
and the lease has 12 years to run, therefore I cannot be paid for any export I produce, that all goes to the "rent-a-roof" company.
There
might be scope for going from deemed export to measured export, which could let you claim for the generation from your own array. It'd depend on the original contract with the rent-a-roof people. Probably best talking to an expert on that.
Re: Negative Revenue
Posted: Fri Jan 30, 2026 11:22 pm
by PhilipLBrown
Jimmyrn85 wrote: ↑Thu Jan 29, 2026 9:11 am
Good morning all, I have a newly installed system on the garage with a Fox H1 G2 5.0kw inverter. 7x 445w panels at the moment but there is plenty of scope for adding more down the line.
I have setup in the app my tariff, which is purchasing lecci from the grid at 0.239pence per kw/h.
For context, I have an existing "rent-a-roof" system which was installed before I purchased this house and the lease has 12 years to run, therefore I cannot be paid for any export I produce, that all goes to the "rent-a-roof" company. I just get to use any lecci I want. I will install a battery on the Fox system at some point.
So with that in mind, why do I get the odd days showing negative revenue? What is that? I would like it to show me for every kw/h produced by the new system that I've saved 23.9pence.
Your advice/thoughts would be appreciated!
Re: Negative Revenue
Posted: Sat Jan 31, 2026 10:00 am
by Jimmyrn85
Interesting WyndStryke, thanks for the response.
Philip, I don't see a reply?
Re: Negative Revenue
Posted: Sun Feb 01, 2026 11:44 am
by Jimmyrn85
Hi all, yesterday we had a decent day of sunshine down in Devon and generated a chunk of lecci.
It's given me negative 55pence in the app revenue. How does that work and what does that mean?
Is there some confusion with the rent-a-roof system going on?
I see PV production for the Fox system as 5.10kWh
To Grid 7.40 kWh
Load Consumption 7.40kWh
From Grid 9.70kWh
Re: Negative Revenue
Posted: Sun Feb 01, 2026 4:11 pm
by retsplines
I think the language they use around this part of the system is a bit weird.
"Revenue" as far as Fox is concerned is basically:
The "would-be" cost of any energy you generated on-site and used (they call this "Solar Savings")
plus The profit from any feed-in
minus The cost of any energy used to charge the battery from the grid.
The last two items combined are called "Feed-in Revenue" by Fox.
Here, your "Solar Savings" are showing as negative, which is a bit weird... The only way I can think of that happening is if the tariffs are configured strangely (negative buying price for a period for example)... Maybe post a screenshot of the Tariff page (from the App home screen, tap Total Revenue, then tap Tariff top right, then tap on the tariff plan you have set up there, and screenshot the chart shown?)
Re: Negative Revenue
Posted: Sun Feb 01, 2026 8:14 pm
by Jimmyrn85
Thanks, appreciate any help or insight you can give me because I'm finding it odd too!!
I updated the tariff page, it was set at 0.239pence per kWh a couple days ago but actually we purchase lecci at 0.251pence so I've now updated that see my attached screenshot.
Since this small system has been installed in early Jan, the PV production has been 55.40kWh.
So I would expect it to say £13.90 (55.40x0.251) worth of lecci has been generated since installation - appreciate we won't use every last ounce of it sometimes but it would give a bit of indication anyway
Re: Negative Revenue
Posted: Tue Feb 03, 2026 11:57 am
by retsplines
Yeah that looks perfectly normal... very weird.
If you log in to the Fox ESS Cloud stuff (
https://www.foxesscloud.com/v2/) is that any more sensible?
To be honest, when I first got our system online, the Revenue thing was all out of whack for a few weeks too. Kept displaying £0.00, then changed to something unbelievable, now it's fairly sensible, but I do constantly doubt it...
Re: Negative Revenue
Posted: Tue Feb 03, 2026 12:05 pm
by Jimmyrn85
Seems normal however I have just noticed something, in "about plant" there is a Feed-In Unit Income. This was set as 0.251pence. We don't get paid for any feed in (that all goes to the rent-a-roof people on a deemed export).
Let's see if that makes any difference!
But at the moment, the total revenue displayed is slowly going down! lol