The Solar Thread

It’s Huawei, you think it’s going to the grid but really your giving China free energy 😉

In all honesty after my experience with Huawei enterprise level networking kit, there’s no way I’ll every buy anything of theirs. Ok the support was good if you class sending out software engineers to rewrite their code on the fly as the products don’t work as advertised (or as tendered) 😁

Ok the support was good if you class sending out software engineers to rewrite their code on the fly as the products don’t work as advertised (or as tendered)

To be fair, we’ve done exactly the same 😉

100A, that’s 23kW

not 100amp at 50v its not .

equally your car is likely NMC technology for its high charge/discharge/volitility (and thus combustability)

house batteries these days are LiFePo – which is much more suited to a permanent domestic setting

Ok the support was good if you class sending out software engineers to rewrite their code on the fly as the products don’t work as advertised (or as tendered)

Just reminded me, 20 odd years ago we were developing a new product and needed to test interoperability of an interface, so were hunting round looking for kit. I thought ‘you can’t go wrong with Cisco’ so we bought a router and cards for standard X. Only when it arrived it didn’t work, filed a support query to be told it didn’t work, they sold a non working interface card which basically did nothing. They did eventually get it working, but in the mean time we used a Chinese cisco rip off* box (which had working SW)!

Bought in China, made in china, but ran iOS and only had an English interface!

What a great thread, some really useful info in here!
We’re installing a 32 panel array with 7.5KW battery and car charger at the end of April. With the green technology discount in Sweden (20% on panels, 50% on batteries) maxed out for this year, we’re thinking of adding modules to increase the battery capacity in 2024. Is this an electrician job or can I buy and install myself?

DIY for Fox batteries, don’t know about others.

The battery is a Growatt, if that helps…? 😏 😁

32panel?! Blimey – in full sunlight that’s what? 13kWp?

LG aren’t quite plug and play…

You’ve got to make the most of the sun when it does shine in Sweden! The panels are split over east/west/south facing roofs so should spread the generation over the day, is the thinking anyway. 😏

Is this an electrician job or can I buy and install myself?

There are two aspects to that; how difficult is it, and what laws or other restrictions may apply. Are you interfacing your panels with the mains supply, or are they stand alone? Do you plan to export power back to the grid? In the UK, your system has to be certified if you wish to export, which means you need to use an installer who can provide the certificate. I don’t know what is the case in Sweden.

Sorry, my original post was a bit unclear. The installation is all done by a company specialising in solar. The electrician or not question was only referring to the bolting on of extra battery modules. 👍

I think (but I may be wrong) that in the UK extra battery modules would still need to be notified and certified if you are exporting.

No, you can DIY extra batteries without restriction in the UK.

OK then, I stand corrected.

Can you mix and match battery manufacturers?

No. These aren’t dumb batteries, they have a BMS to which some inverters can talk. Most/all inverters need to know the model of battery they’re interfaces to. There’s no option for multiple types.

Technically, a G99 is submitted with a specification and wiring diagram which shows the batteries and their capacity. If it changes, you should update it. Whether anyone does or even if it’s a requirement, I don’t know, just that the specs for your g99 are technically wrong if you expand.

Morning Folkes, has anyone any experience with Libby battery / control systems. My local installer has put together my quote based on them.

Technically, a G99 is submitted with a specification and wiring diagram which shows the batteries and their capacity. If it changes, you should update it. Whether anyone does or even if it’s a requirement, I don’t know, just that the specs for your g99 are technically wrong if you expand.

Mine is incorrect, the installer filled in the wrong battery size. Not that anyone cares / will ever notice….

I haven’t really put alot of thought into this and wondered what more experienced people’s views were please.

I have 12 panels on a feed-in tariff in a East-West valley, they generate on a sunny day this time of year 10Kw a day but my house tends to use most of it. I guess it’s not as perfect as it seems with key generation being over the middle of the day and majority of use being either end of the day, and height of summer likely being closer to 20Kw a day.

What would you do? – add a battery to capture it all to ensure that it smooths out the usage and provides a back-up at the same time? Any views on size of battery I should be considering please? I had thought of a solar iboost type thing but if I’m honest feel like the battery is a better option.

Thanks and apologies, i’m at the musing stage so willingly admit I haven’t done any research!

What would you do? – add a battery to capture it all to ensure that it smooths out the usage and provides a back-up at the same time?

The battery will allow you to use 100% of what you generate and also charge at cheap rate overnight during winter, so you can use cheap electricity all day.

They generally don’t provide a back-up unless you install extra kit as you need to isolate your solar system from the grid in the event of a power cut.

However, the economics of a battery are pretty marginal, a 10 kWh battery will cost you £5k+ and that’s a lot of kWh of leccy to pay for itself….

NB We have a battery and it’s great, but the cost doubled the overall installation cost, which pushes payback years out further and the amount it saves us is pretty marginal. Very ‘green’ (we don’t use any peak hours leccy all year round), but not very cost effective…

We specced a 10 kWh battery and our daily usage is between 6 and 12 kWh (12 is when we do all the washing at the WE and tumble dry if it’s raining etc).

Thanks footflaps, I appreciate the pragmatic reply. I anticipate there are some that make it work as hard as possible but I have a personality weakness that it would consume me so I’m keen not to become one of those! 🙂 It’s why I’ve avoided going onto a variable rate tariff as i suspect it would end in divorce.

Maybe the cheaper iboost type device fits my needs that would divert excess generation into heating water would be a better solution. Least not because I have a hot tub to support but I’m not entirely sold on the idea of a lead for a submersible heater coming from the front of the house (where my solar generation meteris) and the back (where the dirty sex pond is).

When I originally specced our system, the battery made complete sense as the best export tariffs were offering 5-6p/kWh, so it made sense to store it to use later: it actually improved the ROI term from 11.5 years to 7.5years. Now with Octopus Flux, it’s a MUCH harder proposition and I’m not sure it makes as much sense, or at least not for a massive battery. Maybe somethign small to keep you off the peak hours.

It’s why I’ve avoided going onto a variable rate tariff as i suspect it would end in divorce

We’re on a dynamic tariff – Octopus Agile.

I’ve just set ours up to do a partial charge between 3 and 5 am, if the battery is below 60% and if not, do nothing. It hasn’t charged now since the start of the April, but prior to that it would top up after overcast days, so we always had enough to get past peak hours (5pm-7pm) every day on the battery.

Initially I did use to look at the rates every day, but lost interest after a while.

Least not because I have a hot tub to support but I’m not entirely sold on the idea of a lead for a submersible heater coming from the front of the house

ex colleague of mine – in stonehaven scotland is maintaining his sex pond at standby currently with 2 flat plate solar thermal collectors on his shed roof

his solar PV provides the pump electric.

at this time of year he suppliments it with grid electric to raise it to in use temp.

by mid may it’ll be pretty much standalone between the Thermal and PV.

He could have gone PV for the whole lot but it would have consumed all his PV generation.

When I originally specced our system, the battery made complete sense as the best export tariffs were offering 5-6p/kWh, so it made sense to store it to use later: it actually improved the ROI term from 11.5 years to 7.5years. Now with Octopus Flux, it’s a MUCH harder proposition and I’m not sure it makes as much sense, or at least not for a massive battery. Maybe somethign small to keep you off the peak hours.

I’m not sure that makes sense. I think of the battery as a capacitor. There is lot of low grade power in the 3-600watt above your base load coverage that would be wasted or only be supplementing load – you cant run a washing machine or dishwasher on that output but after a few hours you have gathered enough electric to cover a load. then in winter the ability to charge at the low rate and run through the high rate – low rate being 10-15pence lower than the higher rate.

Iboosts etc are the bit that doesn’t make sense with the addition of flux – its cheaper to use gas than to heat using what could have been exported electric.

Yeah, but I have a wife who won’t make the calculation. She’ll just look at a badly stacked, only really half full dishwasher and start it regardless of the battery condition.

But fundamentally, I do agree that the battery smooths over the spots in generation caused by cloud/intermittent sun, but I’m saying that if the difference in export to import is only 10p through the majority of the day, The fact that I use 12kWh a day, shouldn’t size the battery, a smaller battery, saving a ton of money makes more sense.

Say for example, my 13kWh Battery was £6800 and a 5kWh Battery was £3k. I need to figure out if that £4k is worth it. At 10p/kwh difference between export and import, That’s 40000kWh worth of power I’d need to store to make back the difference. I’m not going to do that in 10 years, probably not in 20.

A 5Kw battery would, as you say act as a capacitor and get me through the peak period, thus making the best of the system without the massive buy in costs of larger batteries. I’ve got nearly 20kWh here now, but had flux been available in January, I might not have installed the additional 6.5kWh.

Thanks all, really good info. I forgot to mention I don’t have a smart meter so the assumption made by FIT is that only 50% of what is generated makes it to the grid. I suspect where we win in winter we lose in summer so it’s a fair arrangement.

Hmm, all I’ve worked out is it’s yet another subject that’s beyond my brain matter! 🙂

I don’t have a smart meter so the assumption made by FIT is that only 50% of what is generated makes it to the grid

We do have a smart meter, but Eon still work on the 50% assumption rather than using the data.

if the difference in export to import is only 10p through the majority of the day

A friend of mine is on (I think) Octopus Agile and Outgoing Agile – if he has spare capacity he can charge his battery at the lowest import and discharge at the best export rate. There were a few times over the winter when the import rate went negative; he was paid to charge the battery and then paid again to discharge it. I suspect it requires a lot of work to optimise it, either manually or setting software, so it may not be realistic.

I’m not sure that makes sense. I think of the battery as a capacitor.

Great way of looking at it. With Octopus Go, 4.6kW of solar, 5.2kWh battery, and an EV the average price I’ve paid for electricity over the winter is 8p/kWh. This did need some planning ahead with things like running the dishwasher and washing machine overnight though. Heat pump tumble dryer also made a big difference.

There were a couple of power cuts in the village, but the battery kept the oil boiler and freezer going (hard wired into the EPS port on the inverter), and the TV / lights on via a long extension cable. It’s actually easier and cheaper to protect stuff like the broadband router using a £50 UPS from Amazon.

Just applied for this years Solar Together scheme which is closing soon (Kent). Really wish I’d gone ahead with the quote I got a few years ago as I’m sure prices will have rocketed now due to demand etc. won’t get the price though until they do the auction mid-June.

Just applied for this years Solar Together scheme which is closing soon

tread carefully .

a quick sniff around the solar facebook groups and the solar together schemes often come up at astronomical rates as well as subject to sub contractor shoddyness……

like most goverment implemented schemes – it seems the the wee wee is extracted mercilessly.

Yeah, just applied for a quote at the moment. The price I got did a few years ago did seem keen. I did see a few posts on the local FB last year where people seem to have had their installs repeatedly delayed (after paying deposit) but possibly that was just down to huge demand (I know they closed the books on the scheme last year as oversubscribed). Will defo investigate thoroughly before parting with any cash!

often come up at astronomical rates as well as subject to sub contractor shoddyness……

I would think it’s less likely to be over priced if the scheme is well run and gone to an auction.

I had quotes from a local installer (Chiltern Solar) and Solar Together Bucks. Chiltern Solar were about 10% cheaper and seemed more clued up.

Thing is there must’ve been hundreds if not thousands of ST installs locally but can find very few reviews etc online either good or bad. Might have to pop up a Q on local FB page.

This guy not happy though 😬
https://forums.moneysavingexpert.com/discussion/6217540/solar-together-kent-good-scheme-good-quote-for-a-12-panel-system-avoid

Chiltern Solar were about 10% cheaper and seemed more clued up.

yeah will defo get some quotes in from local and/or recommended companies. I’d never use a plumber/electrician/builder etc without a recommendation so this isn’t any difference really!

This guy not happy though

You always expect those who are unhappy to make more noise than those where it all went as expected though, so if you go looking for complaints you just find confirmation bias….

I’d never use a plumber/electrician/builder etc without a recommendation so this isn’t any difference really!

Although if you’re going through a managed scheme, you would expect that the organisers would have done some due diligence and have the ability to hold the supplier to account on your behalf…

Yeah I appreciate that. Reviews on Trustpilot are fine, on the whole. I suspect the key thing is which company has been contracted to do your actual install though, rather than the administrators of the scheme!

Currently waiting for Energy Saving Trust loan (£6k solar + £6k battery) – 11 panels going to go on roof and trying to figure out best battery option…

Daffy
Full Member

Say for example, my 13kWh Battery was £6800 and a 5kWh Battery was £3k. I need to figure out if that £4k is worth it. At 10p/kwh difference between export and import, That’s 40000kWh worth of power I’d need to store to make back the difference. I’m not going to do that in 10 years, probably not in 20.

A 5Kw battery would, as you say act as a capacitor and get me through the peak period, thus making the best of the system without the massive buy in costs of larger batteries. I’ve got nearly 20kWh here now, but had flux been available in January, I might not have installed the additional 6.5kWh.

I’m looking at pretty much this calculation at the moment – whether to go 5/10/15kWh battery when our daily usage is ~20-22…

looking at battery spec, some have 10000 charge cycles, some have >6000… thinking this needs to be checked for the 40000kwh worth mentioned above to check battery wont be goosed before it has paid for itself? 40000 / 5kwh = 8000 cycles so 6000-10000 is critical?

Do you just assume 1 charge per day or will it be charging once on solar and once through night? effectively halving the life of the battery?

My basic calc is that instead of electricity being 34p/kWh, it will be 12p, so 22p saving if run through battery x 90% efficiency / depth of discharge reduction? = 20p saving at today’s prices…

5kwh battery x 365 x 20p = £365 return each year per battery?
Libbi 5kwh battery = £3200, therefore 8.7 year payback?
10000 cycles / 365 (once per day) = 27 year lifetime!?, though more likely to be twice a day?

Growatt is £2500 cheaper for 10kwh setup, £2100 for extra battery (i.e. £4600 more for the same capacity), less power in and out and >6000 cycles for the lifetime. Installer is pushing libbi as the much better system / work better with the app and zappi… more like a 5.7 year payback on the growatt if they function well enough?

Also looking at specs on foxx / pylontech / puredrive which have been recommended by other installers… quite a variety of cost / lifecycles / ratings

Looking back through my historic energy rates:
2016 – 10.21p
2017 – 12.33p
2018 – 12.37p
2019 – 12.37p
2020 – 15.09p
2021 – 14.88p
2022 – 27.84p
2023 – 33.91p

Will batteries continue to make sense for next 10 years? More chance of rates rising than falling or will wholesale market adjust to renewables?

Currently waiting for Energy Saving Trust loan

more info on this please? (apologies if you’ve already given it & I missed it!!)