What system to go for (take 2)

Hi,

I posted way back in the summer asking for advice on my proposed system. Well my system was due to be installed tomorrow but that is no longer happening as the survey we had was wrong and advised the wrong system in the wrong location. We have now had a second survey done but the proposed options are quite different so I'm after some advice.

Original system was 12 * 345w in roof panels, 12 tigo optimizers, with a hybrid 5 inverter and 9.5kw battery, EPS circuit with automatic switch over. This was due to be installed on our garage roof. However it turns out the report was wrong in stating the 2 roof aspects were SW and SE facing when in reality they are SW and NE facing. £13.5k total cost

New system is 18 * 400w on roof panels on the roof of the house which is south facing, 8 tigo optimizers. Solis Dual 6000 Inverter, Giv.AC 3.0 inverter, same 9.5kw battery, no mention of EPS so not sure if it's included or not. £18k total cost. We have the option to reduce the number of panels to 12/14 and going with the hybrid inverter also, not sure what the cost of this would be.

Forgetting for the moment the £4.5k cost difference between the systems. I'm looking for advice on what would be the best system to install. We would like an EPS with automatic failover that has some of the house circuits connected to it.

It's my understanding that the max output of the hybrid inverter is 5kw, where as the AC coupled system would be 6kw from he panels and 3kw from the battery. Also that we could only charge the battery as 3kw, so if we are generating 6kw of power from the panels and the house is using very little we would only be storing 3kw and exporting the other 3kw?

Is this limit likely to be an issue, or is the AC coupled system better on balance? And does the maximum output of the system as a whole outweigh the 3kw battery charge/discharge limit?

If the AC system is the better overall system I will go back to my installer and negotiate on price, as there have been several screw ups from them resulting in no system being installed as it should have been tomorrow and we are currently out of pocket a few hundred because of this.

Just want to make sure I'm getting the best system before I start negotiating. Thanks for any input.

ZmGahH6yQBe curious that you need 8 optimisers across 18 panels on a single aspect. If you want to reduce costs, do you really need these with two strings on a single roof?

stevelewis there are 2 strings, we have a valley roof, so 2 south facing aspects, one will have 10 panels and has no shading, the other will have 8 panels and can get shade from the chimney and other parts of the roof at times.

I notice your original quotation included EPS - presumably because you want to be able to run stuff in a power cut? Perhaps someone else can confirm as I thought I read this somewhere but have not been able to re-find it - "with the AC3.0 system the EPS will run from the battery until it is exhausted. With a hybrid inverter the panels can continue to generate electricity from solar to keep the battery topped up -so the house EPS runs from a mixture of solar and battery while the sun is out". Is this correct? If so this may be something else to take into consideration.

Correct. As the panels and solar inverter will need to powerdown and isolate themselves from the grid when it goes down. They will be attached to the main consumer unit and not the EPS circuit and this is a network requirement to remove the risk of engineers working on the network getting zapped by current inserted into the network by the solar inverter.

Well, I think the AC coupled/hybrid choice has become a non-issue now. When looking into the system further I realised there was no way they would fit 18 panels on the 2 sections of roof. I went and measured myself and looked up the size of the panels and worked out we can only fit 11/12 panels on the roof which would put it into the hybrid inverter camp, so it would be pretty much the same system as we had specified for the garage roof, just in a different location.

I've given the installers one last chance to get it right or I'm going to cancel the install and get a refund.

If you want to look at how many panels might fit you can try using
https://easy-pv.co.uk/home
Just click "Get started" and select "trial project". If you know the size of your roof, and the rough orientation ( from google maps) you can try out all different sizes and makes of panels to optimize your generation. I used it to check that what my installers were offering was feasible.

Karen thanks, this is so helpful. I'd been looking for something like this but couldn't find anything