Solar PV + Battery quotes

Martyn1981

Solarchaser said:

Actually having read Coastalwatch 's contributions again, it seems that there is a president for the dno accepting inverter capping, so looks like it will all be grand, and I'm waffling on about nothing.

Always good to cover things in detail when there are rules, penalties etc to comply with.
What are your thoughts on battery sizing, as I'm talking from a theory perspective, which may be miles away from reality. If summer led, then I was thinking one days storage was enough as PV tends to be very consistent, perhaps 50% to 150% of daily expectations, so no need or point in scaling to cover multiple days.
But, for the winter, where gen is more typically 0% to 200% (per day of average target), would it make sense to scale for 2 days evening/night consumption?
I should say I basing this on CT's very large PV system. In my case, being E/W split, there simply wouldn't be enough excess to consider more than one days worth in the winter, so balancing of demand and supply would become more important.

Coastalwatch

In terms of how larger a battery then taking matters to the extreme I wondered just how large a beastie I'd require to to soak up all that summer excess to store up for winter. Ridiculous of course, however we can but dream!

I guess with the four hour window of cheap rate overnight leccy, then a little over one days domestic consumption might be the most cost effective solution for size of battery.

On the other hand if only V2G were readily available at a sensible price then many of us might have a solution sitting on the drive!

Solarchaser

I think battery sizing is an individual thing tbh.
My 17kwh is too much for summer, but not enough for winter.

But thats 6 people in a house, and so lots of washing machine, dryer etc usage.
I average 20kwh a day over the year.

The last two weeks I've been charging batts overnight and using during the day, but still buying another few kwh's,  unless the solar helps out.

The ideal would be 2Mwh battery, as that would likely take me through summer without buying anything, and see most of winter out, but thats ridiculous. 

They just arnt really cost effective just now. But im looking forward to seeing how much my stack has saved over a full year come March.

EVandPV

Solarchaser said:

They just arnt really cost effective just now. But im looking forward to seeing how much my stack has saved over a full year come March.

We've had our batts about a fortnight short of a year. According to the Lux web portal stats, we've produced 2288kwh from the pv (about 100kwh short of inverter figure) and exported 227.5 kwh suggesting pretty much 90% of generation used.
Bit tricky working out what the batteries have saved but as a rough back of fag packet calc, I'd say about £270-£300.
Got a nice surprise when I checked our pv efficiency on Pvoutput.org the other day. Currently sitting at 2.499kwh/kw for the year. In our first year (2012) it was 2.566kwh/kw so not much degradation going on there !

JKenH

EVandPV said:

Solarchaser said:

They just arnt really cost effective just now. But im looking forward to seeing how much my stack has saved over a full year come March.

We've had our batts about a fortnight short of a year. According to the Lux web portal stats, we've produced 2288kwh from the pv (about 100kwh short of inverter figure) and exported 227.5 kwh suggesting pretty much 90% of generation used.
Bit tricky working out what the batteries have saved but as a rough back of fag packet calc, I'd say about £270-£300.
Got a nice surprise when I checked our pv efficiency on Pvoutput.org the other day. Currently sitting at 2.499kwh/kw for the year. In our first year (2012) it was 2.566kwh/kw so not much degradation going on there !

That looks quite a decent return.

I got my own fag packet out and was thinking in summer with your size battery I could probably save around 5 kWh a day (demand limited) from solar - (180 days x 5 = 900 kWh) which on Go at 13.3p would work out about £120 and in winter, based on one full overnight charge after round trip losses, time shift about 6kWh a day over 185 days x 6kWh = 1110kWh @ 8.33p saving about £92 so total about £212. I do have quite high consumption though.

Presumably the very good Agile rates helped in the summer, with 2020 exceptional because of Covid. 

JKenH

EVandPV said:

Solarchaser said:

They just arnt really cost effective just now. But im looking forward to seeing how much my stack has saved over a full year come March.

Got a nice surprise when I checked our pv efficiency on Pvoutput.org the other day. Currently sitting at 2.499kwh/kw for the year. In our first year (2012) it was 2.566kwh/kw so not much degradation going on there !

You sure? I’m jealous.

Solarchaser

EVandPV said:

Solarchaser said:

They just arnt really cost effective just now. But im looking forward to seeing how much my stack has saved over a full year come March.

We've had our batts about a fortnight short of a year. According to the Lux web portal stats, we've produced 2288kwh from the pv (about 100kwh short of inverter figure) and exported 227.5 kwh suggesting pretty much 90% of generation used.
Bit tricky working out what the batteries have saved but as a rough back of fag packet calc, I'd say about £270-£300.
Got a nice surprise when I checked our pv efficiency on Pvoutput.org the other day. Currently sitting at 2.499kwh/kw for the year. In our first year (2012) it was 2.566kwh/kw so not much degradation going on there !

This year has been fairly bright,  as was last year, I've managed around 3.4Mwh for both, the two years before were around 3.2Mwh.
(Though I did wash them with an extendable brush last year, so that may have helped)

With seeing your figures it pushed me to check mine at effectively the end of month 9.
I had a look at my old inverters data, as they have only solar data, whereas the newest ones have overnight charging.
Old inverters show a total of 2659kwh discharged from batteries.
2659 x 15p = a saving of £398
For just around a month I've been using the new inverters to charge overnight.
They have discharged a total of 474kwh.
If I assume a round trip efficiency of 80% then that 474 x 9p is a saving of £42 this month.

So for the 9 months I've had the larger battery bank, its saved me £440 that I would otherwise have had to buy, regardless of solar generation. 
Generation will be marginal next 3 months, so I can probably roughly extrapolate the next 3 months to be same as last month, so that £42 becomes £168 for darkest 4 months, adding that to the £398 brings to to a rough saving of £566 for the year, just from batteries.

This gives about an 11-12 year ROI.

I'm pleasantly surprised by this. 
They might be financially viable after all. 

Edit. Last time I did this I gave a 10% of loss figure for discharge from solar, which I didnt do here (I searched back)
So the £398 becomes £358, then adding the grid charge (already factored in round trip losses) at £168 brings total to £526 giving a 12-13 year payback assuming all works past that time.

cool_techie

Dear Forumites,

Following you advice, I was all set to sign with Installer 1, for - 30 x 350W Trina (all Black) panels (10.5kW system) with 2 x 3.5kW pylon tech batteries, 1 Solar Edge inverter, 30 solar edge optimisers and iBoost for £11k. 

This with a DNO cap of 5.6 kW.

However, out of the blue, Installer 2 (Deege solar) has contacted me this morning, enquiring about my progress and come up with an updated offer as follows:

Installer 2: 29 x 370W Uleca (all Black) panels (10.73kW system) with 1 x 9.9kW Growatt battery and iBoost for £12.5k.  
32 x 380W (JAM72S03 PERC Half-Cell Module) panels (12.16kW system) with 4 x 2.56kW cobalt free ARK 2.5L Growatt battery and iBoost for £12.35k (DNO check yet to be done)

So given the increased generation and storage capacity, would you recommend this one over installer 1, albeit at a higher overall cost? I am impressed with the capacity of the panels and the fact that the batteries themselves are cobalt free and new technology, but the costs are also now reaching upper limit of my budget!

Apologies for the continued questions. It is just that this process has proved much longer and with more twists than I expected. House buying was slightly easier

Thanks, CT

Martyn1981

Interesting. Those batts seem to come with a 10yr 6,000 cycle warranty.
I'm always in favour of the bigger the better with PV, but you are going seriously big, so there will be more and more capping. However, as costs of generation fall (by going bigger) capping becomes less important, and dare I say, something to be solved in the future as BEV's rollout, batteries get cheaper, and so on and so on.
On paper the new deal looks better. It may be too big, but 'better to regret the things you've done, than the things you didn't do" ....... perhaps?

Solarchaser

I like the idea of cobalt free, would definitely remove some of the battery guilt.

However a couple of things jump out.
1.Solar panels are a standard size (almost exclusively) so why when your previous quote was for 29 panels, do they suddenly think they can fit another 3? Hmmm

2. You had mentioned before you had shading issues, and the solaredge would be beneficial. 
A quick t'internet search says the modules are around £60 each so over 30 panels (the other quote) there is a good £ grand+ of kit there even wholesale prices.

I've very recently come to the realisation that my second system shading is pretty bad in winter, and although I have twin peak panels which reduce the shading effect, im still seeing a big hit when I could really use the extra leccy.
(I think I'm going to see if i can pick up a couple of cheap 1.5kw inverters to replace my 3kw single mppt one)

And so its with this thought in mind id say the time you need leccy most is in dead of winter, and that will be when days are shorter and shading is worse... so that would be when the solaredge would shine (sorry for the pun).

If I were you, I'd go back to first quote, explain to them about second quote and persuade them that you would be more inclined to go with them if they throw in a 3rd battery.

Gotta be worth a shot 🤷‍♂️