Hello, We already have a 6.3kw PV array on the house with battery storage. We are wondering if it would be viable to add a further 4 panels, about 1.4kw, onto the garage roof. The garage has a 2.5mm underground feed from the house and a small CU. I believe we could use the existing cable to feed the garage generation from the inverter back to the house but that it could not be recorded on our fits meter or utilised to charge the batteries. Can anyone confirm that is the case? Also if we decided to run a new cable from the new garage inverter to the house and via the fits meter, a distance of about 30metres, would there be a noticeable voltage drop ? and what size cable would be best?

Assuming it is grid connected, and you have the appropriate inverter and safety isolators, what does your local DNO say about an increase in capacity?

18 minutes ago, lakelandfolk said:

Hello, We already have a 6.3kw PV array on the house with battery storage. We are wondering if it would be viable to add a further 4 panels, about 1.4kw, onto the garage roof. The garage has a 2.5mm underground feed from the house and a small CU. I believe we could use the existing cable to feed the garage generation from the inverter back to the house but that it could not be recorded on our fits meter or utilised to charge the batteries. Can anyone confirm that is the case? Also if we decided to run a new cable from the new garage inverter to the house and via the fits meter, a distance of about 30metres, would there be a noticeable voltage drop ? and what size cable would be best?

If this is an MCS registered installation and you have a FiT agreement, you are NOT allowed to touch the existing panels, inverter or meter, other than to replace like for like in the event of a failure.

Technically you can swing past the FiT generation / export meter and do as you say by feeding into the garage CU, but it is the greyest of grey areas. If you break the agreement, expect some severe consequences.

FYI if your solar panels are 300w each, you are ONLY allowed to replace a failed unit(s) with 300w or less. 305w replacement is illegal.

Basically delete this thread and do as your first suggestion.

Looks like it's not worth the expense and hassle. it is MCS installed and we have a FIT agreement dated December 2016.  Many thanks