PV on an outbuilding belonging to another property

[John_S]

One thing to bear in mind is that it is likely that the two properties are on different phases of the 'street' supply. Thus it is more likely that the DNO would approve connection to the second property. They would not want to see a huge export on a single phase.

[Woodyeyes]

This is very similar to my plans. I too have a large shed in the garden of my next door property (holiday let). I have room for up to 27 extra panels. I have asked Western Power if I can add to my existing 9 year old grid tied 3kw system and they said they will allow only a further 2kw (as I'm at the end of a LV line). So 5kw max on my single phase supply. They said they would allow a total 13kw of generation export limited to 11kw if I pay for a 3 phase supply to be installed (about £4k).
They also pointed out I can have as much PV and battery storage DC coupled behind the AC inverter as I like as long as the inverter is limited as above. I'm not entirely clear what this means in practice though.
(Both my properties are currently fed by one single phase supply)

[cojmh]

I think .... and I am sure someone else will correct me if I am wrong... that on a 3 phase supply you are limited to an additional 10KW inverter (assuming they are counting your existing 3KW inverter in the 13KW limit) and that this 10KW inverter would be limited to 8KW maximum export (again assuming that 3KW of the 11KW allowance is with your initial PV installation).

However you would be allowed to have as many panels as you like (within reason) connected to the second hybrind inverter and as much battery capacity installed to the hybrid inverter as you like.

Hopefully that makes sense.

Not entirely sure what it would mean if you stayed on the 5KW single phase allowance (as the additional inverter would be limited to 2KW?)

I called Western Power today to enquire and they said they could have a quick look for a general idea of what might be possible (not able to commit until a formal application is made though).

From what the lady told me, there is already a lot of solar on the phase and it is likely I would only get an additional 0.5KW on top of what I have already. So it is looking likely that I would not be granted any additional export capacity.

I enquired about the have 3 phase and apparently from the way everything is laid out they would need to bring power cables across the road - so I suspect this is going to be very expensive and not viable.

They are going to check things with their team and see if there is anything they can advise, but it does not look like I will be able to get any extra export capacity. Which means that whatever I install will have to be zero export.

[marshman]

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[Stinsy]

Thanks for all the answers.

I suspect there is a bit of nuance here:



In a situation with 5KW of panels would this inverter still be able to use the 5KW of solar power even given it's 3.6KW inverter? I am just a little confused about the amount of panels it can take versus the rating of the inverter. Sorry if that is a thick questions.

Thanks,

3.6kW is a perfectly acceptable inverter size for 5kWp of panels!

Firstly your panels rarely generate their rated power, and even then only for short periods. In blazing august sunshine the panels jut get too hot and in winter the sun isn't strong enough even when it does shine.

Next a hybrid inverter will divert excess onto the batteries. So if your panel are producing 4.6kW while your BEV is charging, or your electric shower is being used, 3.6kW will go towards the demand and 1kW will go into the batteries.

The Solis 3.6kW hybrid will only charge the batteries at a max of 3kW no matter how much PV you have, read the datasheet under max battery charge/discharge. The 3.6kW is max inverter output to grid.

I don’t remember suggesting differently?

[marshman]

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[cojmh]

Thank you both for your responses.

I had a chat with a friend last night (Smegal) regarding this and realised that I might be looking at this all wrong.

Since installing batteries my export rarely exceeds 1KW and the maximum I have seen is 2KW ish (and this will go to zero when the solar diverter is finally commissioned - incidentally this is about half of what the solar diverter can "divert").

Given that this second system will be similar size, with the same orientation etc. and the same battery stack (4 x US3000C) I am guessing that export will not be massive either. Which means that 5KW might still be more than enough for none to be "wasted".

I guess it will come down to how to work out the export limiting (Assuming that I am unlikely to get any more export capacity). Am I right in thinking that because the inverters can see what is coming/going to the grid through the CT clamp, that the second (new) inverter will be able to export based on what it sees through the CT clamp (so effectively the newer inverter can llimit itself based on what the older inverter is outputting). Or is the export limiting on the newer inverter based purely on a figure that you set where it will not export more than that given amount irrespective of whatelse is happening (i.e. the first older inverter).

I have looked in the inverter model that I am thinking of (SOL-6K-RHI-48ES-5G-DC) but I cannot see an answer to this unless I missed it.

My current export permission is a G59/3 - not completely sure what that means as a standard or if this will affect what I can do.

[Gareth J]

Out of the box idea;
-Put then new panels and inverter onto the garage roof and connect it to the rental house's supply.
-meter the amount of kWh that goes to the rental property and charge them a rate, say, 10p/kWh. Install a solar diverter there too.
-push any excess not captured by the rented house into some batteries of your own.

I'm not entirely sure of the reality of a setup like this, but if you could achieve it, everyone would be a winner. Your tennants get cheaper electric, you get a half decent payment for export.

[cojmh]

Out of the box idea;
-Put then new panels and inverter onto the garage roof and connect it to the rental house's supply.
-meter the amount of kWh that goes to the rental property and charge them a rate, say, 10p/kWh. Install a solar diverter there too.
-push any excess not captured by the rented house into some batteries of your own.

I'm not entirely sure of the reality of a setup like this, but if you could achieve it, everyone would be a winner. Your tennants get cheaper electric, you get a half decent payment for export.

It is a good idea and one I had considered for a possible future expansion once I am happy my own supply is as resilient as possible. If I did this then I would put the panels on the house itself.

I am not sure how easy it will be to contract and collect the money (plus how to deal with disputes) from the tenant. Fortunately we have only had good tenants but I guess that luck will run out at some point.

I suspect an easier model would be to just go with the rent your roof style scheme where by the tenant will actually get free electricity but probably only use 25% of the power generated and the export account would be in my name and just cut out any financial association with the tennant.

I am however mindful that EV charging may become a government requirement in the future for rental properties and possibly before the panels have returned their investment. So it is a balancing act if it is going to be an investment.

But I like the way you think!

[Gareth J]

Yes, I can imagine it'd legally be more hassle than it's worth. I'd be more inclined to do it unofficially. But you'd need to have the ability to cut them off and use it yourself if things went sour. With current prices, there's definitely a price point where you could be getting a decent return and your tennants would be mad not to want to buy it.