Retro-fit battery to roof-rent solar panels

philuttley

I've just had a battery installed on existing solar panels. The panels belong to a company who rent my roof space. They aren't happy but I'm told the battery won't affect their export income as their meter measures power from the panels rather than that exported to the grid and their energy supplier pays them for 50% of that power. Is this correct?

[Deleted User]

Yes: the FIT payee will still get FIT payments and 50% deemed exports UNLESS your supplier elects to move you to measured exports. By fitting a battery you may be in breach of contract. What does your ‘rent-a-roof’ contract say about any changes?

Ectophile

It may depend on where the batteries are connected.  If it's an AC-coupled standalone battery box connected to your house supply, then whenever you charge it off solar, that will go through their meter.  They will lose nothing.

If it's a DC-coupled battery, connected to the solar inverter, then electricity used to charge the battery won't go through the meter.  At night, when you use the battery, that will go through their meter.  But any losses in charging and discharging the battery will disappear as heat, and won't be metered.

mmmmikey

Ectophile said:

It may depend on where the batteries are connected.  If it's an AC-coupled standalone battery box connected to your house supply, then whenever you charge it off solar, that will go through their meter.  They will lose nothing.

Presumably if they get the export payments they could lose something if the OP has a smart meter fitted either now or at some stage in the future and they are then required to submit actual readings and lose their entitlement to deemed export? i.e. the panel owner might justifiably be concerned about future income even if there is no change now.

I guess it comes down to the contract between the OP and the owner of the panels. If the OP has breached this agreement then the supplier has the right not to be happy - but conversely whether the panel owner is happy or not is irrelevant if the OP hasn't strayed outside the agreement.

[Deleted User]

Ectophile said:

It may depend on where the batteries are connected.  If it's an AC-coupled standalone battery box connected to your house supply, then whenever you charge it off solar, that will go through their meter.  They will lose nothing.

If it's a DC-coupled battery, connected to the solar inverter, then electricity used to charge the battery won't go through the meter.  At night, when you use the battery, that will go through their meter.  But any losses in charging and discharging the battery will disappear as heat, and won't be metered.

They might:

https://forums.moneysavingexpert.com/discussion/6438059/smart-generation-payments

matt_drummer

Ectophile said:

It may depend on where the batteries are connected.  If it's an AC-coupled standalone battery box connected to your house supply, then whenever you charge it off solar, that will go through their meter.  They will lose nothing.

If it's a DC-coupled battery, connected to the solar inverter, then electricity used to charge the battery won't go through the meter.  At night, when you use the battery, that will go through their meter.  But any losses in charging and discharging the battery will disappear as heat, and won't be metered.

I'm sorry but not much of that is correct.

A generation meter records the generation, it does not matter whether there is a battery fitted.

Any use of stored energy in the battery will not register on the generation meter.

To fit a dc coupled battery a change of inverter would have been required and that would be in breach of the FIT contract and would have needed permission. A hybrid inverter would be needed to install a dc coupled battery.

I am almost certain that an ac coupled battery would have been fitted and that will have no effect on the generation ofr the deemed export.

If the inverter has been changed, then I would expect trouble ahead if prior permission from both the panel owner and the FIT payer has not been obtained.



@Ectophile, it appears I am wrong about the location of the generation meter in a dc coupled system.

mmmmikey

matt_drummer said:

Ectophile said:

It may depend on where the batteries are connected.  If it's an AC-coupled standalone battery box connected to your house supply, then whenever you charge it off solar, that will go through their meter.  They will lose nothing.

If it's a DC-coupled battery, connected to the solar inverter, then electricity used to charge the battery won't go through the meter.  At night, when you use the battery, that will go through their meter.  But any losses in charging and discharging the battery will disappear as heat, and won't be metered.

I'm sorry but not much of that is correct.

A generation meter records the generation, it does not matter whether there is a battery fitted.

Any use of stored energy in the battery will not register on the generation meter.

To fit a dc coupled battery a change of inverter would have been required and that would be in breach of the FIT contract and would have needed permission. A hybrid inverter would be needed to install a dc coupled battery.

I am almost certain that an ac coupled battery would have been fitted and that will have no effect on the generation ofr the deemed export.

If the inverter has been changed, then I would expect trouble ahead if prior permission from both the panel owner and the FIT payer has not been obtained.

I think maybe you've misread @Ectophile post and/or aren't aware that it's possible to have batteries upstream of the generation meter? (Not meaning to be contrary or argumentative as it's obvious from your other posts that you know about this stuff, I just think maybe on this occasion you may have missed something?)

Specifically, with a DC coupled system energy stored in the battery can register on the generation meter when the battery discharges if the battery charging and connection is upstream of the meter. My Powervault, for example, can be connected in that way. Energy from the panels goes to the batteries until their fully charged and only then does it start to flow through the generation meter. When the batteries start to discharge they do so through the generation meter and this will indeed register - but of course it's only energy that's previously been generated by the panel and it's just being recorded later in the cycle, nothing is being double counted. The downside of this configuration is that you get slightly lower FIT payments because of the losses in charging and discharging the batteries. You can still charge batteries connected this way from the grid if you want to, as long as you have a bi-directional generation meter that counts down when electricty is flowing the wrong way.

The upside is that overall the system is more efficient since with an AC coupled system the energy goes through and inverter then through a charger to the battery and then out through another inverter, whereas with a DC coupled system it goes through a solar charge controller into the battery and then out through an inverter.

As you say a DC coupled system would bypass the original inverters and it seems highly unlikely that any installer other than a fly by night cowboy would do this without the specific permission of the panel owners, so most likely this is an AC connected system that makes no difference to the generation meter's operation, also as you say. In turn, this wouldn't make any difference to the export payments if they are deemed.

But as has been pointed out in earlier posts even if export payments are currently deemed they may not always be and as such the solar panel owner does have skin in the game and the right to be miffed if the OP is doing something without permission that could potentially reduce exports in the future.

matt_drummer

Hi thank you for your comments and explanations.

I am not totally familiar with dc set up and I don't know why the generation meter couldn't be installed between the panels and the battery?

I was really just focussing on whether a hybrid inverter or just a battery charger had been fitted such as the one I have.


Anyway, I apologise to you and @Ectophile

matt_drummer

Apology to @Ectophile, I should have thought before I typed, sorry again.

philuttley

Thanks for all your comments. I didn't seek permission from the panel owner as the battery installer assured me that it would not affect their arrangement. Perhaps I was a little naive. The panel owner is insisting that the installation be returned to normal with me paying the costs of that. I am seeking the views of the battery installer, via my solicitor. Whilst I am sure that there is a contract between me and the panel owner, I have never been given a copy of that. However, I'm not that fact will help. Who knows?

matt_drummer

Could you tell us what was actually fitted?

It may not just be the panel owners that will have a problem with the changes to the system.