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On-grid domestic battery storage
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This thread may be helpful, I did it a few months ago to outline what I had seen with a year of batteries.
https://forums.moneysavingexpert.com/discussion/6111409/a-year-with-home-batteries-and-more-solar-and-an-ev
And in comparison to that thread, since ive been 3 months with 2 lux systems and 17kwh of batteries, instead of buying 650kwh in last 3 months, (last years) I've bought 265kWh so around 90kwh a month, which will be mostly the electric showers, as the two inverters can't cover that, but these are the sunny months, so that won't last all year.
4kw sse since 2014 and 6.6kw wsw / ene split since 2019
24kwh leaf and Lux 3600 with 17kwh useable storage
Install 2: Sept 19, 600W SSE
Solax 6.3kW battery
With high consumption of electricity, especially in the evening, as pulpdiction has said theirs is, the case for batteries is stronger not weaker imo, as the batteries will be cycled almost every day, making the offsetting of electricity cost at its maximum.
Add in a time of use tarrif for the winter months, like octopus agile, and you can lower the winter bill by say 50 - 60%
For me, the case for batteries (and more batteries) is much stronger for high usage as you can maximise their usage, and weaker for low consumption as you would struggle to cycle the batteries every day, making the roi much longer.
4kw sse since 2014 and 6.6kw wsw / ene split since 2019
24kwh leaf and Lux 3600 with 17kwh useable storage
I'm a heavy user. I currently consume the vast majority of what I generate, with the little spare on top going into batteries. However I am soaking up loads of battery charge when it's cheap / free / paid for overnight, and my battery kicks in during the day to supply power if electricity prices are high - all of this controlled by octolux. On Octopus, I basically import 0 energy between the 4-7pm window when it's most expensive, and the battery trickles into the house if prices go higher than 7p/kwh.
Lux + 3 x 2.4kWh battery storage. Installed Mar 2020.
Location: Bedford, Roof: South East facing, 20 degree pitch
Nissan Leaf, TADO Central Heating control
For the last 3 months I've spent a total of ~£45 on electricity which works out at around 55kwh/month at 14.7p/kwh and then the standing charge.
The vast majority of this will be using electric showers which use more electricity than the lux inverters can cover, and some will be days of poor generation.
At the moment my standing charge makes up 40-50% of the monthly bill depending on the month.
So for April, May and June I paid for ~165kwh (326kwh last year according to sofar, I can't tie up the bills from last year due to edf/bulb smart meter disputes)
Using the lux data (ct clamps)
Gen 3460 (last year was 3005 according to sofar)
Export 1406 (last year was 1160 according to sofar)
Unfortunately I was not recording the smart meter export every month, so cannot say how true the figure is/was. Smart meter says 1550 this year vs the 1406 on lux ct clamps. (10% out)
And so consumption of around 1946kwh for this 3 months. (Please note I am not using the consumption figure from the ct clamp data as its garbage due to the parallel/not parallel operations of the lux) plus 165kwh bought.
If I had no solar i would have paid ~£285 not inc standing charge
My fit 4Kw system generated 1450kwh in this period, and so it could be argued that fitting the second system last year has saved me 500kwh that I would have had to buy, so £73 (assuming I used all the fit system gen and batteries caught all export... unlikely, so in reality the second system will have saved quite a bit more im sure)
According to the lux the battery output has been 980kwh, so a little over half of my 1946kwh consumption, and so from the batteries directly, a saving of £144.
Now there's no denying there is a fudge factor here, as some of that battery output is lost in the inverter, but it varies from 30w to 400w depending on output, and so i guess maybe a 10% fudge would be reasonable, so £130 saving purely from the batteries.
I'm more than a little annoyed with myself that the data i recorded was not as consistent or as complete as I thought.
So what does it all mean?
Not really that clear. The fact i exported more than last year would suggest the additional batteries are doing not very much at all, though there is clearly additional generation also.
I think it says that I am not using the full amount of the batteries each day or the battery figure would be 91 days x 17kwh = 1547kwh, though the figure is roughly 2/3rds of that suggesting around 10-12kwh is likely about right... and thats what I've always thought (got 4 batts cheap on ebay, so "had" to buy them 🙄)
However it does show that the 6kwh batts I was using last year were not enough as 91 x 6 = 546 so roughly 55% of the last 3 months discharge.
Its fair to say covid is messing things up also as there will be more daily consumption due to tvs being on, lunch cooking instead of school meals.
So to sum up it seems the additional batteries and inverters have made a marginal difference... however what it doesn't show is the undoing of the "solar optimisation" that those of us with solar panels tend to do.
No more putting the washing machine on at midday etc (which was always a fight with the white goods lover) the house runs exactly as it would if we had no solar.
If the tumble dryer, dishwasher and washing machine are to go on at the same time, all good, crack on, and that has made a difference in terms of friction between geeky solarchaser and white goods lover wife, and reducing friction in married life during a lockdown is no bad thing, let me tell you!!
4kw sse since 2014 and 6.6kw wsw / ene split since 2019
24kwh leaf and Lux 3600 with 17kwh useable storage
Anyway until today it did seem to be working OK but today I isolated it (both from AC and DC to install the feed for my 'maintained' supply contactor from it's non grid output. I've failed to get it to re-energise since. I've proven that there is electricity on the 'grid connection' but the screen doesn't come no, nor do you hear the relays in it clunk closed when it works out it needs to charge / discharge. I'm also switching to the Agile Tariff (smart meter install Weds) and do NOT want the batteries to feed into a load I end up creating (I've a 40Amp feed to a second consumer unit in an office in the garden earmarked for this!) I don't think there is anyway to control the SOFAR via software so I was thinking of a simple hardware mod that switches the SOFAF CTs inputs to a dummy one suggesting that solar is generating and there is little load demand hence it will try to charge the batteries until they fill! Does the Lux have a similar setup of a solar and grid CT, is it easier to control via software? Can someone recommend a good model / hardware supplier of it. I would like to have the option to buy more batteries if they drop in price. Does it also cope with 8 packs like my existing one?
Hopefully I can use the leverage of eBay to get a refund on the SOFAR!
Thanks
Chris
From memory I think batteries need to be on (and running) and then you give it mains.
Sofar won't really work with agile, however several of the forum members are using the lux running a script (not gonna lie i don't fully understand it) to integrate with octopus tarrifs, so it really sounds like thats more what you are looking for.
Plus the lux switches on with either battery or mains (vs sofar requiring both).
There was a good YouTube video on how to configure the WiFi using your phone by think renewables/ gigabiz/ homeswitch/infinity/pv pro, might still be there, was like 10 mins.
I couldn't find it, but this one should help
The solar man app can grab data from the sofar, but really the lux is better as you can actually set charge and discharge limits/cycles etc with the lux app, whereas the sofar can only show you information.
The lux can take 8 batteries yes, though Michael from think renewables etc did tell me they can now take unlimited batteries... ive not seen that confirmed anywhere.
4kw sse since 2014 and 6.6kw wsw / ene split since 2019
24kwh leaf and Lux 3600 with 17kwh useable storage
Thanks
t
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