@batalto, which batteries do you have?

I track my system month my month and then break it down into an annual sheet (attached). When I installed my PV I opted for a hybrid invertor (Sofar ME3000SP) and 2x US3000 Pylontech batteries (3.5kwh each) with an 80% Depth of Discharge (DoD). The cost of the invertor and the batteries were lowered due to the 5% VAT on install at the time and there was little cost increase to go for a hybrid vs normal invertor. My batteries were £800 each due to the VAT and the supplier I got them from - 7kwh for £1,600

There is no way a 10kwh battery system costs £10k. Pylontech US3000 can be had for around £1000 each (after VAT). You can buy a 10kWh kit on ebay for about £5k (again after VAT).You can see the total cost of my 8.4kw PV array and battery was £10,800, that's panels, batteries, labour etc. However we were having our roof done so I already had the scaffolding. I also sourced the panels myself from a solar farm which had unused excess panels so a massive saving vs retail. If I had used a company to supply everything it would have cost far more.

The calculations below are real outcomes of my system live. Battery for me gives me about 30% of my total power use. Unit costs for my elec is around 14p. Year one isn't a true year as the system was installed in May. At the bottom you can see a full year for year one, that runs into year 2 but is a May to May calculation. Hopefully this is useful for you and give a real world outcome. Clearly if you are paying an electrician to come and do all the work there is a greater cost. Mine went in at the same time as the PV system so the cost for labour was negligible. 

Happy to answer questions

Ok. I understand. Your system cost was £10.8k, of which the battery was included. Battery cost is a lot smaller % than I thought. Good. It is the nett savings that pay back the total system price. Which looks like a 10 year payback. It is and the right thing to do today. And I would encourage anyone who is getting PV today to buy a battery as well. 

But when I purchased my 4kW PV, the return was based on the FiT. (For me a 4.5 year payback). 
For me to add batteries now would be a higher cost, which I can’t make work. I still think V2G is my best solution. 

My spare PV goes into heat my hot water via a Solic 200 electric diverter. 

I'm  able to confirm that shortly the saltwater batteries will soon be available in the UK. The factory have taken production from China to an in house facility in Austria and are in the process of ramping up production. The prices a couple of years ago were about £1800 for a 2.4 kWh battery stack. They are made from 100% recyclable material which you can take to your local refuse tip.

I've been using the older, larger 2.2kWh successfully for about 3 years with no problems.

Chris

https://www.bluesky-energy.eu/en/greenrock-home-2/

@chris-in-kemnay, do you know what the approximate life of these batteries is?

@editor Don't quote me Mars as I don't have the promo material to hand. But I think it was something like 75% @ 3000 cycles.

If you search for Aquion  S20  which is what I have. I'm fairly sure that's the figure you come up with. There are so youtube videos and webinars available  in English as well as German.

Check out Dale’s YouTube channel SpectrumGeek

YOUTUBE.COM "https://youtube.com/c/SpectrumGeeks"

Before you continue to YouTube

He’s had a large solar PV installed and battery and tracks usage and return. I think he was aiming at 10 year payback but I thiggst had come down to 8 years 

Just to correct my last statements..the output is now 2.7kWh and 70% after 15 years and 100% at 3000cycles, 80% at 5000 cycles. Plus scaleable to far beyond what the  homeowner would need.

Greenrock BA-S1-24 Salt Water Energy Storage 24V 2.7kWh

• Supplier Part No: BA-S1-24
• Capacity:, Standard solutions of 5 kWh – 30 kWh, Project-related solutions up to 1MWh
• Voltage: 24V and 48V, Single-phase or three-phase, AC or DC coupling possible
• C-Rate: 0.2
• Round-Trip Efficiency: 90%
• Depth of Discharge DOD: 100%
• Lifespan: 15 years (@ 70% usable capacity)
• Cycles: @ 100% DoD > 3.000 cycles / @ 80% DoD > 5.000 cycles
• Temperature range: -5°C – 50°C
• Communication: Modbus TCP
• Weight per kWh: 60kg + 1x junction box 30 kg
• Line-up: Indoor
• Guarantee: 10 years
• Applications: Own consumption of solar power, wind energy, Emergency power, Off-grid island solution
• Additional points to consider: No separate structural measures needed, No requirements regarding transport = harmless merchandise

@chris-in-kemnay these seem expensive, large and not as good as the Pylontech US3000 (as an example). Whats the £/kwh?

@batalto That's the downside of them,  they are large, but completely recyclable at your local tip.

I can't give you an exact figure for the new Greenrocks as that will depend on the importer. Im expecting them to be around the  £1800 for 2.7kWh mark. Hopefully under £7200 for 10.8kWh But my larger yet smaller  Aquion S 020's were £1250 each new. I bought another  3 with 3000 cycles  on them which  cost me £1000 with transport costs.

So for me I get about 7.5kWh for £3500.

Yeah that's almost double the price per kWh that I paid for batteries