Do I need a battery?

[GaryMG4]

Like @tsedge I have been following the solar/battery/EV discussions here and have been considering adding a house battery.
We have a 4kW solar array installed by the previous owner on FiT, it generates 3.7-4.2 kWh per annum. Last year EDF paid £910 in generation and deemed export payments and I paid Octopus £730 for the grid energy consumed so I'm up on the deal. Over the summer I managed to consume 38% of the 3MWh generated.
In another discussion someone queried if I had a battery to buffer the solar generation when clouds come over and that got me thinking, how could I squeeze more out of my solar.
Option 1, get rid of deemed export and go for SEG, that would net me another £150 but at the risk of falling SEG rates. my installation has 14 years of guaranteed payments to run and there's an even chance I will expire before it does.
Option 2, run the Zappi on Eco rather than ECO+ to make the most of the solar at the risk of using more than 25% grid top up, at which point it equates to a cost close to 7p kWh so I might as well charge overnight.
Option 3, add a battery. A free standing (AC coupled) battery appears to be around £5k for 10kWh. I don't know if this would be able to be wired such that it could provide the buffer to keep the Zappi happy and although 10kWh is a reasonable fit for daily consumption it is too small to accept a good days generation of 20-25 kWh.
Option 4, wait until (if) the solar inverter fails and replace it with a hybrid that I can a battery to.

 

[JohnV6]

I am just doubling my battery capacity to 8.4 kWh. I am on IGO so I charge the batteries overnigh to 100% at 7p per unit if needed and when the sun shines I get 15 p export. I charge the car at 7p per unit.

4.2 kWh isn't enough to cover a cloudy winters day hence the increase as the supplier is selling off the last units of our older battery type.

Working out a payback is difficult but I reckon sub 6 years so better than the bank

 

[Bam Bam]

Like @tsedge I have been following the solar/battery/EV discussions here and have been considering adding a house battery.

Oooh, interesting question.

We have a 4kW solar array installed by the previous owner on FiT, it generates 3.7-4.2 kWh per annum. Last year EDF paid £910 in generation and deemed export payments and I paid Octopus £730 for the grid energy consumed so I'm up on the deal. Over the summer I managed to consume 38% of the 3MWh generated.
In another discussion someone queried if I had a battery to buffer the solar generation when clouds come over and that got me thinking, how could I squeeze more out of my solar.
Option 1, get rid of deemed export and go for SEG, that would net me another £150 but at the risk of falling SEG rates. my installation has 14 years of guaranteed payments to run and there's an even chance I will expire before it does.

My neighbour is an electrician and thinks that if he added a battery to his FIT solar array he would have to declare it as a change in the system and would then lose the good payment rates. Not sure if that is 100% gospel though.

I know some people have been giving up their FIT payments as it is better in the short term. But I think the SEG rates are likely to drop at some point as more solar parks get connected to the grid.

Option 2, run the Zappi on Eco rather than ECO+ to make the most of the solar at the risk of using more than 25% grid top up, at which point it equates to a cost close to 7p kWh so I might as well charge overnight.
Option 3, add a battery. A free standing (AC coupled) battery appears to be around £5k for 10kWh.
I don't know if this would be able to be wired such that it could provide the buffer to keep the Zappi happy and although 10kWh is a reasonable fit for daily consumption it is too small to accept a good days generation of 20-25 kWh.

Probably could be made to work, but you'd have to check with your installer (and hope it isn't the same one that Rolfe has who didn't seem to be able to come up with the common method to get things working together).

Option 4, wait until (if) the solar inverter fails and replace it with a hybrid that I can a battery to.

Any chance you could add another solar array somewhere (garden, fence, wall?) and put a hybrid inverter on that?

As you say you've already got a big battery in the car, so making use of that is an obvious option.

But I generally recommend to people that they get a battery, particularly if they have an EV and thus qualify for cheap overnight charging.

Essentially, I would double check with the FIT people if adding an AC coupled battery would impact on your deal, and if it does not then consider that.

Let us know what you decide!

 

[Fokmg]

If you add a battery to your fits system you will effectively loose your payments, they tend to assume that they get 50% of what is generated.

Often they now use the smartmeter to report the real export which if you use you power well should
be minimal or you can arrange to export power at premium times .
As my original system was fitted at the end of FITs I only got about £200/ year. I made the decision to go big on the battery and fitted x2 Tesla Powerwall (27KW) and ignore FITs
I use Octopus Go intelligent and in the winter month fill the battery at 7p/ unit (this year we ended up buying about 30 units at standard charge) and our average power cost with the Solar works out at about 4p/ unit. Our household does use a lot of power (10Mw= / year)
This year which has be exceptional has generated nearly 5.9 Mw (we lost abot 40Kw down the grid)
With storm Dara we kept the house running for 5 days without mains (but reduced loads).

I have so little confidence with the grid systems these days the more I can control my own destiny the better.

,

 

[Fokmg]

Another point relating to FITs installations, if you use a charger like a Zappi you should also notify them of its installation, it is very much like a battery and is seen to harvest some of the power that the FITs would have expected.
Again if you accept your "Output" FITs payments to be determined by a smart meter ther is no issue
Hope this helps
I think they have just realised that they have been paying for power they never recieved since the advent of smart chargers and batteries oops !

Happy New Year

 

[GaryMG4]

Some interesting points there. Amongst the notes on the Octopus site where they mention stand alone batteries it mentions that if a battery is added FiT may need to be informed and it is certainly the case if you replace the inverter or panels.
Deemed export is based on 50% of your generation so I'd guess they reckon you are self consuming 50%, but even trying quite hard last summer I only managed 38% with most days being 20-25% at best.

'Again if you accept your "Output" FITs payments to be determined by a smart meter ther is no issue' Not really sure about this as FiT is made up of two elements generation and deemed export, what you are describing is just SEG. There is a separate generation meter that is used to supply the readings, I think for larger installations they required an additional export meter although that could now be taken care of by the smart meter.

I do have the roof space to add a completely separate system althoughI'm not sure the DNO would accept more output in my area or how SEG would apply to the new system while the old one was also adding to the output.

 

[JohnV6]

I added batteries as a separate inverter. My solar array hasn't changed so no need to inform anyone.