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Hi All,

Looking for some guidance on what to do next


I have 2.2kW yet to install that i was going to grid tie in the old fashioned way, however as this isn’t in yet was thinking about the future, when I go down the battery storage route.

My PV generation isn’t great, with another 1.7kW 2011 install.

Busy clearing space under the floor boards/under connsumer unit area for general insulation improvements and further future projects came to mind.

Space would be ideal for batteries &. Inverter, DC route would be a challenge but not impossible.

Was thinking about using the off peak intially to charge the batteries to prevent using peak electricity, but then thought shouldn’t the 2nd PV system be tied into this too.

Anyone any experience if this type of set up.
Anyone with an inverter outputting more than 3.6kW
Thinking the Pylontech route would be best due to flexibility/ known pedigree etc.

Thanks in advance for any tips.

Similar ideas going round and round in my head.

Do you have an EV?

Intelligent Octopus and Octopus Outgoing completely change the game. At least 6 hrs charging at 7.5p per kWh and export at 15p.

In other words, if all the second PV is exported, you are still ahead of the game.

Yes, I have an EV and currently on intelligent octopus

The 2nd system will be a diy system, so probably no export for this.

Jut trying to work out things in my head, available space for equipment etc..

If you are going to use the power in real time e.g. for the EV or for export then invert straight to AC. But you will need DNO approval even if all you are doing is displacing consumption from the original PV so that it can export. Unfortunately 3.9 kW is just over the 16A limit for connect-and-notify (if that route still exists!)

If you are going to store it for use later then better to have a hybrid inverter and convert straight to DC. Avoids need for further DNO approval. AFAIR there are inverters which will work in this way even without buying or connecting the batteries yet.

I have some of each which has its advantages.

But if you have not got the batteries yet or are undecided then going AC will give you some useful generation while you sort the rest of the project out.

What’s your actual inverter rated at on the original 1.7kW install ?, if you don’t know do you know the model number ? If your existing and the proposed added together don’t exceed 3.68kW, then job done, DIY and no need to notify assuming the original one was notified.

Your panels can add up to whatever the inverters will take and can exceed 3.68kW, it’s not relevant to the DNO.

nowty wrote: ↑Sun Oct 22, 2023 3:29 pm What’s your actual inverter rated at on the original 1.7kW install ?, if you don’t know do you know the model number ? If your existing and the proposed added together don’t exceed 3.68kW, then job done, DIY and no need to notify assuming the original one was notified.

Your panels can add up to whatever the inverters will take and can exceed 3.68kW, it’s not relevant to the DNO.

Can't the panels be as big as you have space for, so that they give full output as far into the shoulder months as possible, but just "stall" at the inverter's max power in high summer? (i.e. they can add up to more than the inverters will take.)

nowty wrote: ↑Sun Oct 22, 2023 3:29 pm What’s your actual inverter rated at on the original 1.7kW install ?, if you don’t know do you know the model number ? If your existing and the proposed added together don’t exceed 3.68kW, then job done, DIY and no need to notify assuming the original one was notified.

Your panels can add up to whatever the inverters will take and can exceed 3.68kW, it’s not relevant to the DNO.

It’s a SB1700 inverter
Original set up on FIT

AE-NMidlands wrote: ↑Sun Oct 22, 2023 3:46 pm

nowty wrote: ↑Sun Oct 22, 2023 3:29 pm What’s your actual inverter rated at on the original 1.7kW install ?, if you don’t know do you know the model number ? If your existing and the proposed added together don’t exceed 3.68kW, then job done, DIY and no need to notify assuming the original one was notified.

Your panels can add up to whatever the inverters will take and can exceed 3.68kW, it’s not relevant to the DNO.

Can't the panels be as big as you have space for, so that they give full output as far into the shoulder months as possible, but just "stall" at the inverter's max power in high summer? (i.e. they can add up to more than the inverters will take.)

I think the max VDC is 400 volts on this single string inverter.

sharpener wrote: ↑Sun Oct 22, 2023 12:05 pm If you are going to use the power in real time e.g. for the EV or for export then invert straight to AC. But you will need DNO approval even if all you are doing is displacing consumption from the original PV so that it can export. Unfortunately 3.9 kW is just over the 16A limit for connect-and-notify (if that route still exists!)

If you are going to store it for use later then better to have a hybrid inverter and convert straight to DC. Avoids need for further DNO approval. AFAIR there are inverters which will work in this way even without buying or connecting the batteries yet.

I have some of each which has its advantages.

But if you have not got the batteries yet or are undecided then going AC will give you some useful generation while you sort the rest of the project out.

The second install doesn’t owe me anything, it’s all bought and paid for years ago, got an inverter too, so maybe it will
Be grid tied for a bit on the inverter I have then possibly storage next.

AGT wrote: ↑Sun Oct 22, 2023 7:01 pm

nowty wrote: ↑Sun Oct 22, 2023 3:29 pm What’s your actual inverter rated at on the original 1.7kW install ?, if you don’t know do you know the model number ? If your existing and the proposed added together don’t exceed 3.68kW, then job done, DIY and no need to notify assuming the original one was notified.

Your panels can add up to whatever the inverters will take and can exceed 3.68kW, it’s not relevant to the DNO.

It’s a SB1700 inverter
Original set up on FIT

I could not work out on a later message whether you have already bought another inverter or not ?

Another SB1700 which can be had second hand for very little money off fleebay would not require any further DNO notification as you would be up to 3.4kW. Then you could later buy a 3.68kW battery inverter and go G99 fast track with the DNO.