That makes sense. They are companies that are on markets for business and for investment. 

Thanks, so I’m unlikely to get them chasing me. You are correct, they have zero visibility of my self consumption, I assume that why they have resorted to vehicle mileage checks at MOT for the new EV charges. 

Indeed, but HMRC subsequently rejected their claim and ruled that all income from Ripple was taxable as they failed the first test listed above:

1. the system is installed at or near domestic premises occupied by the individual

One can also argue that Ripple is not exactly "a microgeneration system" given their size. So income from Ripple is taxable if it exceeds your £1000 side hustle allowance (you should have received a tax statement from Ripple or administrating co-op detailing how much is treated as income and how much is return of your capital)

No different really to the income I receive from holding shares in UK Wind or various solar farms listed on the FTSE - I receive dividends that are subject to dividend tax if held outside of a tax wrapper, or income tax when drawn if held within a SIPP. It's all taxable income one way or another unless held within an ISA.

Regarding income from arbitrage, which presumably does not fall under the microgeneration exemption as you have not generated it, some back of the envelope maths shows that someone with 30kWh of battery storage who is able to cycle their battery once per day may export around 10,000kWh per year, and would need to achieve 10p per kWh arbitrage to generate an income of £1,000. I'm not aware of any tariffs that would facilitate that, although conceivably someone with a large battery system on Octopus Flux could get close if they were able to import and export fast enough during the respective 3 hour windows (minimum 10kW charge and discharge/export rate required).

I would have to check, as the inverter generates AC from DC..

With 30kWh, over 8kW export, optimisation of import and export and on currently available tariffs (assuming the current rates stay roughly the same around the year), it is certainly possible to exceed that yearly income.

But the ROI may be negative specially if 3k or so are expended on MCS related labour and paperwork!

Yes, of course the total income from export could be greater than £1,000, so we need to understand if import costs for arbitrage are allowable expenses to be deducted so that tax is only paid on the profit from arbitrage rather than the total revenue generated. I see these as legitimate input costs into the business model and thus deductible, but I am not a tax lawyer. Then there is amortisation of the initial capital costs.

I would have to check, as the inverter generates AC from DC..

With 30kWh, over 8kW export, optimisation of import and export and on currently available tariffs (assuming the current rates stay roughly the same around the year), it is certainly possible to exceed that yearly income.

But the ROI may be negative specially if 3k or so are expended on MCS related labour and paperwork!

I wouldnt be surprised. 

There is, in principle, a role for arbitrage to help balance grid load, but (at least based on what @transparent tells us) the way electricity is priced doesn't necessarily drive the right technical behaviours. 

From what I understood, these issues depend on the specific substation equipment. And the same argument applies to pv generation.

Could a concern to remove the use of Bess for local grid balancing create an incentive for domestic users to shift the import to other suppliers? 

The reality is that battery systems are a good idea whenever people are planning to install an ashp as it seems very obvious that, given the reluctance of our gov to tax gas (and the way in which it loaded extra costs on electricity), it becomes tricky to claim an ashp will cost less to run than a gas boiler. Removing any incentive to install them is a step against decarbonisation. 

Agreed, and the current direction of travel appears to be to move some of the levies on electricity into general taxation, which whilst it will help reduce the direct cost of electricity does nothing to more heavily tax the dirty fuel that we want to discourage use of. I guess they cannot bear more pictures of pensioners huddled around candle in winter if they add more tax onto gas heating bills.

Getting back to the issue of taxing solar export income, I read many articles in the press leading up to the Jan 31st tax return deadline scaremongering that hundreds of thousands of solar households would have to do a self assessment tax return if they exceed the £1000 income from solar exports, and not one of those main stream press articles mentioned the tax exemption cited above that will apply to the vast majority of domestic solar installations in the UK which is not new legislation having existed since 2007/8.

Further, although energy suppliers can potentially share data with HMRC, they do not know your domestic consumption nor your solar generation figures - they only know your import and export figures neither of which are relevant to determining the exemption or calculation of any tax due. Given the intent to exempt the vast majority of domestic solar installs from income tax, I really do not see HMRC chasing the average homeowner for relatively small amounts of income tax that may be due. It was just an easy story for the press to write in the lead up to the tax deadline.

Regarding income from arbitrage, which presumably does not fall under the microgeneration exemption as you have not generated it, some back of the envelope maths shows that someone with 30kWh of battery storage who is able to cycle their battery once per day may export around 10,000kWh per year, and would need to achieve 10p per kWh arbitrage to generate an income of £1,000. I'm not aware of any tariffs that would facilitate that, although conceivably someone with a large battery system on Octopus Flux could get close if they were able to import and export fast enough during the respective 3 hour windows (minimum 10kW charge and discharge/export rate required).

Well, adversity is the mother of all innovation 🤣