Adding a battery to an 8 year old solar system

JimLad

Hi Gang!

Ive had 4kw of solar panels on my roof since 2014, and its been great, generating 30,000 kwh so far! With my electricity jumping from 13p to 40p when my fix comes to an end in october, I am thinking maybe i should add a battery to the setup.

I have an electric car and am on Octopus go, so ideally the system would take excess solar and also be able to charge at night on the 7.5p rate (this is especially important in winter!).

Has anyone else here retro fitted batteries to an existing solar setup? Just looking for some experiences and estimated costs really. Im assuming the inverter would need changing?

Thanks in advance.

mickyduck55

I added batteries to my system in Feb 2020.. I am delighted with them.  You will need an additional inverter as this will leave your existing system "as is" so no changes to your FIT (if you get it)

A lot of post on here with much more up to date prices things have changed considerably since my install.

I have a split system ASHP (A/C and heats)  I buy VERY little electricity at peak periods and through the reasonable solar months non at all... from my thread
 https://forums.moneysavingexpert.com/discussion/6260671/how-low-can-you-go-daily-weekly-monthly-whatever-electricity-grid-import#latest
you will see quite a few people importing negligible mains power for many months of the year. Is it worth it or not is a matter of opinion if you are on Go or Go Faster maybe load shifting will give you the maximum benefit

JimLad

mickyduck55 said:

I added batteries to my system in Feb 2020.. I am delighted with them.  You will need an additional inverter as this will leave your existing system "as is" so no changes to your FIT (if you get it)

I will have a read through your thread thankyou.

Yes i do get the FIT. Currently 18p for every kw generated and 6p for the "deemed" 50% export

JimLad

So it seems changing the system would mean an end to my FIT payments....think that puts a stop to my enquries!

ABrass

I don't think that's correct.
https://www.solarguide.co.uk/solar-battery-with-smart-meter-will-not-stop-fit-payments#/

You might need to go for a separate AC coupled battery rather than having the option to have a hybrid inverter, but batteries can be added without adjusting your FIT.

In fact, you can add more panels and a larger Inverter and still keep your FIT (more or less)
https://www.ofgem.gov.uk/sites/default/files/2021-12/Feed%20in%20Tariffs_Consultation%20on%20the%20treatment%20of%20replacement%20generating%20equipment_Decision_13122021.pdf

If you had a 2kW system under FIT and then doubled the size of it today you would need to notify whoever pays your FIT. Your rate wouldn't change but you would only be paid for 50% of the power your system produces.You wouldn't get any SEG for the excess power you'd be exporting though. 

EricMears

ABrass said:

If you had a 2kW system under FIT and then doubled the size of it today you would need to notify whoever pays your FIT. Your rate wouldn't change but you would only be paid for 50% of the power your system produces. You wouldn't get any SEG for the excess power you'd be exporting though. 

That would not be a problem if you made sure that the old system remained exactly as it was and any additional panels were added to a new inverter and output not routed through the existing TGM.

It is possible to keep your FIT 'generation payment'  but opt out of the deemed export portion then all exports could be sold under a SEG scheme.

mickyduck55

JimLad said:

So it seems changing the system would mean an end to my FIT payments....think that puts a stop to my enquries!

You will not be changing your system... you be adding a new one... I believe that's why a second inverter is added so there are NO changes to the system that is eligible for FIT

[Deleted User]

Don’t forget that a DC battery (or more properly its inverter) needs DNO approval as it is treated as a potential generator. The DNO will usually want to see a schematic of the proposed installation along with details of the items to be fitted with approvals. For a sum, £350 in my case, the DNO will decide whether to set a site export limit in kW. DNOs are not the fastest operators in the land.

An AC battery gets around this requirement: I have no idea how this would impact on your FIT.

ABrass

[Deleted User] said:

Don’t forget that a DC battery (or more properly its inverter) needs DNO approval as it is treated as a potential generator. The DNO will usually want to see a schematic of the proposed installation along with details of the items to be fitted with approvals. For a sum, £350 in my case, the DNO will decide whether to set a site export limit in kW. DNOs are not the fastest operators in the land.

An AC battery gets around this requirement: I have no idea how this would impact on your FIT.

Isn't that the wrong way around?

DC means before the inverter, so no changes to any possible export to the grid. AC means after the inverter so if it is exporting at the same time as the panels are generating then ou could be pushing too much into the grid.

70sbudgie

ABrass said:

[Deleted User] said:

Don’t forget that a DC battery (or more properly its inverter) needs DNO approval as it is treated as a potential generator. The DNO will usually want to see a schematic of the proposed installation along with details of the items to be fitted with approvals. For a sum, £350 in my case, the DNO will decide whether to set a site export limit in kW. DNOs are not the fastest operators in the land.

An AC battery gets around this requirement: I have no idea how this would impact on your FIT.

Isn't that the wrong way around?

DC means before the inverter, so no changes to any possible export to the grid. AC means after the inverter so if it is exporting at the same time as the panels are generating then ou could be pushing too much into the grid.

I agree. The grid only really "cares" about the inverter output, so DC coupled wouldn't really make a difference to the DNO.

Thevegetarian

I have a system that give me feed in tariff at the highest rate. Been looking to increase the size of the system I have been told by a number of installers that it’s illegal if you want to keep the tariff. My inverter is 11 years old and I was informed if I changed it to a MPPT inverter I would get up to 30% more energy. Sound a lot to me!  I have decided to get a new system independent of the existing one. I have a lot of research to do.