Home Battery with Solar

Magnitio

I have solar and batteries. To maximise the ROI, you need to have it set up correctly and regularly review the tariffs that you are on and those that are available. Unfortunately, there appear to be some who have solar and battery installations where they only charge from solar.  This gives them very little benefit during the winter. It can mean on the worst days their installation actually costs as the inverter and BMS use more electricity than is generated by the solar panels. Installers are pushing batteries as it is good profit for them; they are even pushing battery-only installations with claims of ROI that are only achievable with active management of charging/discharging.

QrizB

SuzeQStan said:

Netexporter said:

There's a rash of small EVs coming on the market at the moment, mostly with pretty decent range. 

So far I've got EV, heat pump and solar plus a share in a windfarm. Just have to live to 95 to get the full benefit of the latter! Batteries, with islanding, this coming year and then I'm all set for the Apocalypse.

How will you prevent potential electrocutions islanding?  

By doing it properly, rather than with a suicide cable?

Netexporter

SuzeQStan said:

Netexporter said:

There's a rash of small EVs coming on the market at the moment, mostly with pretty decent range. 

So far I've got EV, heat pump and solar plus a share in a windfarm. Just have to live to 95 to get the full benefit of the latter! Batteries, with islanding, this coming year and then I'm all set for the Apocalypse.

How will you prevent potential electrocutions islanding?  

Three-pole contactor and local earth.

Martyn1981

Got to say my gut feeling is that the batts, certainly as quoted (which isn't too bad for a PV/batt install to be fair) isn't economical for you.

The problem (so to speak) lies with your low usage. I thought cheap rate charging would help you, but I'm guessing at an annual saving of perhaps £150, so not really enough ..... but again, not terrible either - 20yr payback for green and ethical may be OK, but for money saving, not really.

Is there any chance that in the future you may get a BEV (battery electric car) or perhaps some form of heat pump for space heating? These would not only increase your consumption, but make switching to a dual rate tariff viable. And at that point, the batt being charged overnight in the winter will help.

So, PV, batts, BEV, heatpump, night tariff (probably more) all work together quite well, with the benefits increasing as you add more and more of them.

But there's no real rush for a battery now. It used to be that you got the VAT removed if batts were installed with the PV, but that has now changed, and the VAT is now free on batts so long as you have PV, even if installed beforehand. So you're probably better off leaving it for now, and revisiting as batt costs fall, and/or your circumstances change and leccy consumption rises?

pensionpawn

Read with interest as I've been trying to find a fiscal case for adding a battery (with island mode functionality) since I had my panels installed 9 years ago. A 13.5 kWhr Powerwall (3, 2 and original...) has, depending on prevailing tariffs, around an 8 year RoI for me (at best!) on an annual import of 3.9 Mwhrs, which spookily is currently my metered export! 8 years is too long for me as there are better ways to use £8k (min) in the short / medium term. However having added A/C to my house (lounge and both double bedrooms) in the spring I've come back to check the sums again due to the corresponding import uplift.

I have a 4kW array facing due east and a 3.12 kW array facing due west, with a 6kW inverter and an 8kW export limit. So I have been looking at GivEnergy products this morning and what I would like to know is the most cost effective way for achieving at least 20 kWhrs for storage (6kWs x 3 hrs of peak export rate, with a small buffer), with island mode (inc panel charger during power cut) and at least 8 kWs of peak power (in addition to any solar).

All suggestions gratefully received.

QrizB

pensionpawn said:

All suggestions gratefully received.

Could you swap your current inverter for a hybrid (~£1k) then add a Fogstar 12kWh battery (~£1.5k) or two? Fitting should be less than £1k on top but might not give whole-house islanding (that'll depend on the inverter and electrician).

If the Powerwall option would save you £1k a year, this could save almost as much and give a 4-5 year payback?

Magnitio

Prices like this will make a substantial difference to the ROI:

https://www.fogstar.co.uk/collections/solar-battery-storage/products/fogstar-energy-15-5kwh-48v-battery

pensionpawn

Thanks for the suggestions. How does the Fogstar battery app / weather forecasting - modelling compare with others e.g. Tesla? Also, I should have mentioned that I don't have a garage (it was converted to an internal room 25 years ago...) so it would need to be sited outside, near the meters / opposite side of the wall to the consumer unit, and due to only a 1m spacing between detached houses, 2m off the ground.

Regarding swapping out my current inverter for a battery inverter, as my SolarEdge inverter is in the loft, replacing it with a hybrid would potentially give me sleepless nights, unless I moved it outside. Something I'll leave until it goes pop.

Martyn1981

pensionpawn said:

Read with interest as I've been trying to find a fiscal case for adding a battery (with island mode functionality) since I had my panels installed 9 years ago. A 13.5 kWhr Powerwall (3, 2 and original...) has, depending on prevailing tariffs, around an 8 year RoI for me (at best!) on an annual import of 3.9 Mwhrs, which spookily is currently my metered export! 8 years is too long for me as there are better ways to use £8k (min) in the short / medium term. However having added A/C to my house (lounge and both double bedrooms) in the spring I've come back to check the sums again due to the corresponding import uplift.

I have a 4kW array facing due east and a 3.12 kW array facing due west, with a 6kW inverter and an 8kW export limit. So I have been looking at GivEnergy products this morning and what I would like to know is the most cost effective way for achieving at least 20 kWhrs for storage (6kWs x 3 hrs of peak export rate, with a small buffer), with island mode (inc panel charger during power cut) and at least 8 kWs of peak power (in addition to any solar).

All suggestions gratefully received.

Not at all what you asked, but just pondering 3 things you mentioned, east array, west array and a Powerwall, and it made me wonder if you have room for a small ground mount, or panels hanging off fences etc facing south, for winter generation.

I mention this, as the Powerwall 3 has several MPPT's, so as well as using it as an AC side battery for the existing PV, you could also 'simply' add the ground mount through it, without any additional DNO issues*/complications ...... I think? So potentially a very cheap way to add more PV, well cheap after spending 1,000's on the battery install!

*Just to be clear, when adding an AC side battery you will probably have to get DNO approval, but PV connected to the battery will be covered by the battery approval, and its AC side output.

pensionpawn

Martyn1981 said:

pensionpawn said:

Read with interest as I've been trying to find a fiscal case for adding a battery (with island mode functionality) since I had my panels installed 9 years ago. A 13.5 kWhr Powerwall (3, 2 and original...) has, depending on prevailing tariffs, around an 8 year RoI for me (at best!) on an annual import of 3.9 Mwhrs, which spookily is currently my metered export! 8 years is too long for me as there are better ways to use £8k (min) in the short / medium term. However having added A/C to my house (lounge and both double bedrooms) in the spring I've come back to check the sums again due to the corresponding import uplift.

I have a 4kW array facing due east and a 3.12 kW array facing due west, with a 6kW inverter and an 8kW export limit. So I have been looking at GivEnergy products this morning and what I would like to know is the most cost effective way for achieving at least 20 kWhrs for storage (6kWs x 3 hrs of peak export rate, with a small buffer), with island mode (inc panel charger during power cut) and at least 8 kWs of peak power (in addition to any solar).

All suggestions gratefully received.

Not at all what you asked, but just pondering 3 things you mentioned, east array, west array and a Powerwall, and it made me wonder if you have room for a small ground mount, or panels hanging off fences etc facing south, for winter generation.

I mention this, as the Powerwall 3 has several MPPT's, so as well as using it as an AC side battery for the existing PV, you could also 'simply' add the ground mount through it, without any additional DNO issues*/complications ...... I think? So potentially a very cheap way to add more PV, well cheap after spending 1,000's on the battery install!

*Just to be clear, when adding an AC side battery you will probably have to get DNO approval, but PV connected to the battery will be covered by the battery approval, and its AC side output.

Thanks for your suggestion however there is zippo room for any ground, shed or fence panels. I'm happy with the size of my array, having initially put panels on as much of my roof as I could, in anticipation that in the future having more energy than I need would come in useful, and then Flux came along!

I'm just looking at minimising my import and maximising my export with the minimal amount of cost, effort and stress.