FIT 3Kwp System from 2014. Should I be adding batteries?

[Bob Smith]

I am lost.

Are we talking for the PV system which have FiT, or new installation (after the FiT had gone)?

It is my understanding that if you get a new PV system today without batteries then you MUST have a smart meter in order to be able to sell your electricity.
If you have new PV system + batteries, I thought it was the same but from what is being said above, it seems that since they cannot know how much from the grid has been used to charge your batteries and then what you actually sell,then, smart meter or not they will pay you 50% of what is generated.
OK but at which tariff?

There are a varieties of export tariff from SEG to Agile which pay differently.

 

[Bob Smith]

Brains awash now with data.
I'm trying to collect data together to check what size battery store system I should aim for.

My Smart meter csv data dump tells me I used 2441kwh in 2021-22 & 2086kwh in 2022-23

49% of my daily usage is after 4pm with a surge around 5-7pm cooking, my unit cost is 35p

Daily gross consumption looks to be between 11kwh and 14kwh with the odd 21kwh (xmas day)

Solar generates around 15kwh up to 21kwh daily in sunny summer months with a lot being exported unused for peanuts.

I don't yet have an energy supplier who offers low rate overnight electricity to charge batteries but I guess there will be no problem changing to one who does offer this once I have a system that needs the low tariff.

So its looking to me like 10 to 14kwh battery pack and fast charge 5 or 6kw AC coupled inverter should with summer pv see me mostly grid free except for battery charging.

As to payback period I aim to spend no more than £5k. My current solar exports are worth £650/yr in battery charging mode. The grid use assuming my solar continues to perform is worth around £850/yr if I can use battery instead.
This works out at 3.3yrs to payback the cost of the kit assuming 5k max.

At the end of last summer I installed an 18k btu split aircon unit with heat pump, I've not had much chance to use it yet but that will tax my energy saving!

So am I on the right track so far?

I have followed a similar train of thoughts.

You consider what your acceptable instant power (charge and discharge of the batteries) should be
You consider what is your average consumption as well as the variance between summer and winter.
If you want to size a system to cover all your winter needs, it will be well oversize for Summer and the other way round if you size for Summer only.
You are prepared and understand that you cannot 100% be off grid and that you will need to import electricity either to charge your batteries, or when you instant power needs are higher than what your PV or/and batteries can give you.

This is pretty much how I have also considered sizing the my system.

I will nonetheless add that plan for expansions, That is, you may want to add more batteries in the near future. This is my plan, see how it goes the first year (validate the assumptions I made) and depending how it goes I will add more batteries or not.

 

[Oldman22]

I am lost.

Are we talking for the PV system which have FiT, or new installation (after the FiT had gone)?

It is my understanding that if you get a new PV system today without batteries then you MUST have a smart meter in order to be able to sell your electricity.
If you have new PV system + batteries, I thought it was the same but from what is being said above, it seems that since they cannot know how much from the grid has been used to charge your batteries and then what you actually sell,then, smart meter or not they will pay you 50% of what is generated.
OK but at which tariff?

There are a varieties of export tariff from SEG to Agile which pay differently.

As I titled the thread 3kwp 2014 system, I'm assuming that's what we are using as the base line. I don't intend to loose my FIT in order to add batteries, so I need to be sure what I am allowed to do

 

[MHarv]

To keep your Fit, you are looking for AC coupled battery system great in the summer but for winter if not on TOU Tariff ie Octopus Go tariff 4 hours off peak to charge batteries will be hard to use effectively if at all, only at a standard tariff at peak price not cost effective.

Depends also if you have smart meter for 30 min readings working and connected to your energy provider for TOU tariffs are really required to utilise TOU tariff for the winter period.

Which was my case, smart meter change over to Octopus energy then as I purchased EV moved to their Octopus Go for off peak energy rate, SolarPV install G98 and last October 2022 decided to go batteries G99 Fast Track using Solax X1 AC 3.6kW inverter with Solax Master Battery With BMS V2 LFP and one Solax Slave V2 LFP Battery total 11.6kW to 5 bed Large Detached house double garage for solar Pv and batteries. Only paying now £1.45 daily for 10 - 11 kW Using Octopus Watch and Octopus Compare from between £3.65 to £5.00 so a big saving.

To be honest with electric prices going up will not be coming down soon in the future,
theirs a very tricky alignment to now happen in Europe reference our RED.

 

[Bob Smith]

As I titled the thread 3kwp 2014 system, I'm assuming that's what we are using as the base line. I don't intend to loose my FIT in order to add batteries, so I need to be sure what I am allowed to do

Thanks, you are right.

I am in the same situation. Got mine in 2016 and now want more panels and batteries without losing the FiT. However, as I want be able to paid as I will have to export (my new system will give me about 2.5x what I currently generate, I thought I would need to have a smart meter and therefore lose my "deemed" 50%.
However, the article from Which seems to say otherwise. I will need to do more digging and found out what the regulation actually says.

 

[Oldman22]

Bob, the way I see it, I think you cant add anything to your FIT system like more panels as the generation meter will record a big increase in quarterly readings you supply to your FIT partner. What they cant control is what you do with your "spare" current generation, so exporting to your batteries is fine. If they were to record via a new smart meter that you are not exporting anything that's also fine as the pittance they pay for export you may well be better off feeding your batteries.
Any extra panels you fit would have to be separate to the FIT system into their own inverter.

 

[Bob Smith]

Bob, the way I see it, I think you cant add anything to your FIT system like more panels as the generation meter will record a big increase in quarterly readings you supply to your FIT partner. What they cant control is what you do with your "spare" current generation, so exporting to your batteries is fine. If they were to record via a new smart meter that you are not exporting anything that's also fine as the pittance they pay for export you may well be better off feeding your batteries.
Any extra panels you fit would have to be separate to the FIT system into their own inverter.

You are perfectly correct.
Any additional panels will need to be on a different inverter.

 

[johnb2713]

Brains awash now with data.
I'm trying to collect data together to check what size battery store system I should aim for.

My Smart meter csv data dump tells me I used 2441kwh in 2021-22 & 2086kwh in 2022-23

49% of my daily usage is after 4pm with a surge around 5-7pm cooking, my unit cost is 35p

Daily gross consumption looks to be between 11kwh and 14kwh with the odd 21kwh (xmas day)

Solar generates around 15kwh up to 21kwh daily in sunny summer months with a lot being exported unused for peanuts.

I don't yet have an energy supplier who offers low rate overnight electricity to charge batteries but I guess there will be no problem changing to one who does offer this once I have a system that needs the low tariff.

So its looking to me like 10 to 14kwh battery pack and fast charge 5 or 6kw AC coupled inverter should with summer pv see me mostly grid free except for battery charging.

As to payback period I aim to spend no more than £5k. My current solar exports are worth £650/yr in battery charging mode. The grid use assuming my solar continues to perform is worth around £850/yr if I can use battery instead.
This works out at 3.3yrs to payback the cost of the kit assuming 5k max.

At the end of last summer I installed an 18k btu split aircon unit with heat pump, I've not had much chance to use it yet but that will tax my energy saving!

So am I on the right track so far?

You seem to have a good understanding of your needs. I would suggest you approach from the budget end of the project, start with the £5k and get as much inverter power and big a battery as you can within your budget. If you don't mind a bit of DIY and are comfortable working with electrics, building a battery isn't difficult. Have a look at this video for what's involved, all that's needed beyond what's shown is an inverter. Going this routine you manage 12 kWh with a 5kW inverter for around £4200.

 

[johnb2713]

I forgot the video link...... it's an age thing LOL

 

[johnb2713]

I'm going to have to disagree, my smart meter was installed well after my Solar install, I wasn't with the same provider for FIT payments and I'm still not so although I have a smart meter the FIT company does not have access to my export readings.

No problem at all, I have little (read no) experience of FIT I merely interpreted what was published re export / 50%.

I still get deemed 50%. I also recently enquired with my energy supplier re the latest mk2 if you like smart meters, they said if they installed one there is no obligation to inform any FIT provider that its been fitted. It would of course go on the national database so if a company wanted to find it, my current one is of course on that database but isnt read for export.

Thats good for you, a great situation to be in, you should guard it closely.

 

[Oldman22]

No problem at all, I have little (read no) experience of FIT I merely interpreted what was published re export / 50%.


That's good for you, a great situation to be in, you should guard it closely.

John in the grand scheme the 50% export is no big deal they pay me 6p/kwh exported which in a good year pays around £100. If they started to meter my export and I was clever enough to use what would normally be exported to top up batteries it would be costing me 27p a day to have nothing to export. My daily standing charge is 41p and I shrug that off as there is nothing I can do about it, so 27p can also if need be get forgotten about

 

[Bob Smith]

I forgot the video link...... it's an age thing LOL

Is that you John? Only joking. I know you were just getting started at that time.

Are you preparing your own video?

 

[Oldman22]

Now here is another twist for those on the FIT scheme.
Quote:

Can I combine SEG with other grants and financial support?​

Yes. The only exception is if you already receive payments under the FIT scheme. You cannot receive both FIT export and SEG payments, although you can choose to opt out of your FIT (export) payments and receive SEG payments instead, while continuing to receive FIT generation payments.
https://energysavingtrust.org.uk/advice/smart-export-guarantee/
So anyone here receive more than 6p/kwh in SEG payments?

Also read further from the link re brown energy and SEG

 

[johnb2713]

Is that you John? Only joking. I know you were just getting started at that time.

Are you preparing your own video?

I was going to video my build but I couldnt be bothered in the end. I am considering another battery (which I would make a video) build for some shop premises that we have, I cant make my mind up whether to build a battery or buy a Nissan Leaf, charge it at home and then during the day run V2P at the shop. I would benefit greatly from the very attractive off peak pricing compared to business energy costs. Nissan Leaf Battery 40kWh, so if used 30kWh in the scheme of things that could save me £4300 per year and provide transport for my better half.

 

[Bob Smith]

I was going to video my build but I couldnt be bothered in the end. I am considering another battery (which I would make a video) build for some shop premises that we have, I cant make my mind up whether to build a battery or buy a Nissan Leaf, charge it at home and then during the day run V2P at the shop. I would benefit greatly from the very attractive off peak pricing compared to business energy costs. Nissan Leaf Battery 40kWh, so if used 30kWh in the scheme of things that could save me £4300 per year and provide transport for my better half.

This is a great idea actually. You get two for the price of one.

 

[Oldman22]

Another question, so my original FIT panel system exports quite often, even in winter as my background load isn't much.
If I add a 2nd hybrid AC coupled inverter with batteries charged overnight by cheap rate & topped up by the FIT solar and I don't want any battery power exporting to the grid, how to I do that?
As I see it if I'm not using all my solar and my battery output is to the same circuits it too will get exported.

 

[johnb2713]

Another question, so my original FIT panel system exports quite often, even in winter as my background load isn't much.
If I add a 2nd hybrid AC coupled inverter with batteries charged overnight by cheap rate & topped up by the FIT solar and I don't want any battery power exporting to the grid, how to I do that?
As I see it if I'm not using all my solar and my battery output is to the same circuits it too will get exported.

Set the inverter for zero export it will then not export to to the grid, if it does see an export taking place it will ramp up it's charger to charge the batteries from the excess solar.

 

[Oldman22]

So John this magic happens via ct clamps does it? I suppose it must.

 

[johnb2713]

So John this magic happens via ct clamps does it? I suppose it must.

Yes, it's pretty straight forward really. Inverter see's import from the grid so increases it's output voltage. If it sees export to the grid it will decrease it's output voltage until the export stops, if it doesnt stop it will start up the battery charger.

 

[Oldman22]

Still trying to justify or not spending 5k or more of my savings on a battery store system to reduce my home energy costs.
Using last years imported energy as a baseline, I thought rather than costing each kwh used from the battery to justify purchase, I would first see how much energy is actually costing me now.
I imported 2511kwh @ lets say the rate I pay now which is .336p/kwh plus .406p/day standing charge.

So my costs in 12 months were £843 plus standing charge of £148 Total £991 plus vat @ 5% £1040.

My (long since paid for) solar panels generated around 3800kwh which paid me £790 in that year.

So offsetting my solar payout against my usage £1040-£790 Leaves just £250 as my years electric energy cost.

That's £20/month or 69p/day. Not very much is it.

Now providing my solar keeps producing, its FIT payments subsidize my bill quite nicely.

I do "waste" a considerable amount of my solar generation by exporting it to the grid.
I exported around 2473kwh last year worth at todays rates £830 if that amount was being imported.
The ability to time shift when I could use some of the excess solar via battery storage would be useful but unless I shut down my gas central heating and buy oil filled radiators for every room to use up this in a battery store I cant see payback being any time in the next few years.

The solar wont always fill batteries, in winter I still need to buy energy at say 10p/kwh night rate to charge them each night.
So it looks to me like 15-20yrs payback and I am unlikely to be around to see the end of that!
Looks to me like I need a gas generator

Comments? Have I missed anything?