Solar Panels UK - is it worth it?

[Pete UK]

I've had cheap rate EV charging long before I got solar and battery, so I think for me I can't really claim that saving as part of my solar breakeven calculation. I couldn't see a way that was honest to myself without having some separate metering of consumption on and off peak to compare to actual import - export. For example today I've imported 86p of electricity overnight, but without the battery so far I would have spent £1 by now. that'll likely be about £4 by the end of the day.

Yes I see your point and actually I do now compare it using the existing cheap rate car charging to get a more honest answer for that part.

It’s how you quantify the battery savings from “importing to export it later” and solar generally that’s a bit more subjective. You can look at it many different ways;
1) Did I get paid for every kW I put in the car? …or
2) Was the car charge “free” and I saved mostly on house use?
…or
3) Did I pay 7.5p/ kW to charge the car and all the savings were made in the house?



As long as we’re making savings it’s all good though!

 

[Pete UK]

The one thing I see from reading these comments regarding charging the home batteries at the cheap rate and exporting it at a higher rate thereby increasing the return is the number of cycles being introduced into the battery and the reduced life expectancy of the battery itself.

My Solax Triple power batteries are rated at 6000 cycles, (I have three 4.5Kwhr LI batteries) a cycle being from 10% to 100%, so a 50% charge is half a cycle, I charge them only from solar - so during the winter months there is little solar charge put into them and they seem to hover around the 10% mark - the cut off mark, 9 months of the year the solar and batteries pretty much run the house for free and the generation and Export FIT returns pretty much covers the 3 months where they generate little to nothing.

I could of course opt for whatever the equivalent is nowadays to economy 7 tariff and charge the batteries for a few pence per KWhr overnight and earn a bit more back from exporting that energy during the daytime, but each time you do that your introducing another cycle - which diminishes their lifespan.
What i don't know is the pure economics of it -If the return of those few additional pence is financially better than the cost of a shortened battery life.

The batteries were expensive £6K for the system with one 4.5Kwhr battery and a further £2K for each of the other two batteries - so £10K - this doesn't include the cost of the solar array/inverter/optimisers etc

I installed batteries for my own convenience and not to generate income and i suspect If I was to deploy the constant cheap charging of the batteries overnight and exporting during the daytime that the total income wouldn't compensate or cover the cost of early battery replacement.

I just don't know.

I had my system installed November 2018, The total cost was £14K, (I managed to acquire the additional two batteries which were £2K each for £1K each at the staff reduced price purchase scheme - I wasn't staff but the person i bought them from was) My spreadsheet total cost is based on the £14K figure and all saving are deducted as each month i put my meter reading into it. As of today my return of investment has been £6282.45 - so £7717.55 to go.
I estimate its going to be another 5 years to break even - so 10 years in total - and nowhere near the prediction that Solar and battery adverts lead you to believe by indicating ROI in 5 to 7 years.
I did opt for the best and most efficient system i could buy at the time (I could have saved £4K with a cheapo system) with the hope that it results in longevity and reliability, however, I expect that come the 10 year mark some equipment will be coming to the end of its life and further investment will be needed - like the battery inverter or perhaps a battery, panel optimisers. The panels themselves have 25 yr warranty - LG neon Rs and 20 years warranty on the main inverter - but the main cost items are covered by warranty and any further investment should be paid back pretty quickly.
All I really have to do is live long enough now.

I’m just going on the fact that it’s a 10 year unlimited cycle warranty, so I’ll use it to the max, to get maximum savings over that period and whatever capacity degradation there is after the warranty expires. Well, it is what it is. It might be 20% it might be 30%. Might be totally different. If it’s around 30% degraded then that might still be good for me for another 5-10 years. Also there might be better/ cheaper replacements available.

You got your batteries at a very good price.
Why not use them to the max to get a better return on investment/ save for new ones if/when they degrade?

A lot depends on individual case by case scenarios I guess. Hard to find a one fits all scenario.

Is leaving them at around 10% for 3 months good for Lithium Ion either? Does that degrade them too?

I guess no one really knows.

 

[browellm]

While it's worth noting the detail of warranties - e.g. the GE battery is warranted to be at least 70% of its original capacity within the warranted period - I take the view that life's too short to worry about whether to cycle a battery or not. It's their entire use case.

 

[Drew57]

@GlynG mentioned FIT which also applies to my PV system so I believe the potential of filling at cheap rate and exporting during saving sessions would not be possible unless we forego the scheme and transfer to SEG (but lose the quarterly deemed 50% export payment which wouldn’t justify the switch for me)

 

[Pete UK]

@GlynG mentioned FIT which also applies to my PV system so I believe the potential of filling at cheap rate and exporting during saving sessions would not be possible unless we forego the scheme and transfer to SEG (but lose the quarterly deemed 50% export payment which wouldn’t justify the switch for me)

Yeah, you FIT guys are lucky. Also the higher export rate might not be around for ever, then I’ll be reverting back to “export as little as possible” mode again.

 

[thewishy]

While it's worth noting the detail of warranties - e.g. the GE battery is warranted to be at least 70% of its original capacity within the warranted period - I take the view that life's too short to worry about whether to cycle a battery or not. It's their entire use case.

You're technically correct here, but you need to look a bit deeper into how Giv do their warrenties. https://midsummerwholesale.co.uk/pdfs/giv-battery-warranty-2022-v3.pdf

Warranty is effectively a discount on a replacement battery. The discount on a replacement battery reduces with the age of the battery and further if you've had excessive cycles. (Basically they're saying you should expect a 10 year life on the battery)

If your battery dies at 8 years, you get a 15% discount on a replacement.
Even on unlimited cycle warranties, that's further reduced if you're above about 1.3 cycles per day "fair use". With the capacity limited batteries (2.6/5.2kWh batteries) it's just a cliff-edge maximum number of cycles before warrenty expires.

Odds are if the capacity reduces below 70%, your battery will be old and with higher than "fair use" cycles, which means the capacity warranty is effectively worthless.

In any case, with the warranty policy as it is today, excessive use of the battery isn't free of drawbacks. That said, I think you're probably safe charging up overnight off peak and discharging over the day

 

[yessuz]

Ah, i got simple calculation:
my bill before solar and after. for the same month.

 

[Pete UK]

Even on unlimited cycle warranties, that's further reduced if you're above about 1.3 cycles per day "fair use". With the capacity limited batteries (2.6/5.2kWh batteries) it's just a cliff-edge maximum number of cycles before warrenty expires.

It says in brackets that the 8.2 and 9.5 (100% DOD models, I assume) are exempt from the throughput limit - “fair use”? Which makes sense, otherwise they’d be limited to the same number of cycles as well.

But the rest is correct. I’d forgotten most of that, so not really a great warranty after the first year, no.

One full charge and discharge a day is definitely easily covered on any model, so that’s fine for “importing to export later”.

 

[thewishy]

It says in brackets that the 8.2 and 9.5 (100% DOD models, I assume) are exempt from the throughput limit - “fair use”? Which makes sense, otherwise they’d be limited to the same number of cycles as well.

But the rest is correct. I’d forgotten most of that, so not really a great warranty after the first year, no.

One full charge and discharge a day is definitely easily covered on any model, so that’s fine for “importing to export later”.

I read it as 2.6/5kWh batteries have a drop dead 5000 lifecycle limit, I'm not convinced that the "unlimited" models are excluded from the fair usage reduction for the compensation scheme - they could certainly make a reasonable argument. In either case, it's not a great warranty after year 1.

 

[GRiLLA]

Yes I see your point and actually I do now compare it using the existing cheap rate car charging to get a more honest answer for that part.

It’s how you quantify the battery savings from “importing to export it later” and solar generally that’s a bit more subjective. You can look at it many different ways;
1) Did I get paid for every kW I put in the car? …or
2) Was the car charge “free” and I saved mostly on house use?
…or
3) Did I pay 7.5p/ kW to charge the car and all the savings were made in the house?



As long as we’re making savings it’s all good though!

I think its simpler than that. You have two costs, what it would cost without solar + battery, and the actual cost with solar+battery.

When you charge your car the 'without' cost is the kWh used x price at that time. The 'with' cost is whatever your meter is really saying.

The saving is 'without' - 'with' each day, I calculate that at 23:59 each night and add it to a running total.

 

[browellm]

If your battery dies at 8 years, you get a 15% discount on a replacement.

That's not strictly true either. If the battery doesn't meet it's warranted % capacity, you get a discount. It's not a binary working/not working warranty.

 

[Js1977]

Ah, i got simple calculation:
my bill before solar and after. for the same month.

Thats pretty much it for me as well ...halved my bill

 

[WannabeOwner]

increasing the return is the number of cycles being introduced into the battery and the reduced life expectancy of the battery itself.
...
What i don't know is the pure economics of it -If the return of those few additional pence is financially better than the cost of a shortened battery life.
...
I just don't know.

I don't know either

But ... I think ... I'm going to get a fair few years out of the batteries, regardless of whether I fill them to export daily, or just let them buffer house-use and solar-PV excess. And, I reckon, by then replacements will be cheap (or there will be grid storage batteries and it will be a mugs-game to have your own)

As of today my return of investment has been £6282.45 - so £7717.55 to go.
I estimate its going to be another 5 years to break even - so 10 years in total - and nowhere near the prediction that Solar and battery adverts lead you to believe by indicating ROI in 5 to 7 years.

My ROI is far better than that - about 4 - 5 years. Based on my original plan (back then I didn't know they were going to pay me to export) I use all of my battery, every day, for the house so I pay Off peak for all 24 hours. In summer the batteries fill from PV and I use zero Off Peak and if I drive somewhere I can use up the PV to refuel the cars - I buy almost zero car fuel for 8 months of the year.

My electricity bill is (just a for example) 25% of what it was. That is a saving "forever" (until I have to replace the batteries). Regardless of whether electricity price skyrockets (it has). That is a tax free saving.

So for me, retirement age, I have "hedged" any price change on electricity, and I'm doing my bit to be Eco (which is important to me)

I'm not bothering to calculate the saving at all. What am I going to do with that calculation? I would be interested in comparing cost for my current provider, and A.N.New provider. If I want to brag to my mates I tell them I only pay 25% of my electricity, or I have free fuel for the cars from March through September. Actually they've been hearing that for years (and done nothing), they are now much more envious to hear that I am selling my PV.

Why not use them to the max to get a better return on investment/ save for new ones if/when they degrade?

Yup. That's what I think too. They are installed and paid for now. My aim, with my data, is to maximise what I get out of them - "hypermiling" if you will.

I am interested in how well can I predict tomorrow's sun (badly on, say, 20% of days) and combine that with my planned usage

• Is the car available for charging tomorrow
• Not going to be here
• Needs to be well-fuelled for day-after
• etc.

If pay-to-export stops I will want all that data to optimise for whatever the next best-bang-for-buck method is going to be

 

[Pete UK]

Is the GivEnergy warranty different if a battery physically breaks/ just stops working?
(I assume the inverters warranty is for a full replacement or repair, or extra contribution to the next generation model available, especially as I bought the extended 10 year warranty, to later find out it’s included for free now).

I mean, it’s explained reasonably well (cough cough) about the battery performance guarantee and the “contribution” for a replacement if they degrade more than normal. But what about if they just break/ blow up etc…?

Is that the same deal with the warranty? I’m pretty interested, as I’ve had 2 which didn’t perform properly from day one replaced already. . And there are so many new firmware updates as well ! The AIO has got lots of issues as well. When you’ve got 4x 9.5’s side by side it’s maybe easier to compare the performance but I’m not sure it is when they are in pairs. I personally reckon the AIO has got 4 of the 5.2kW 80% DOD modules in it ! Maybe with an extra 10% buffer at the top and bottom. And the people with problems are experiencing what I experienced with my 4 9.5’s when part of one of them isn’t working right.

I feel that we should all be giving them a really thorough shake down in year one if thats the case. If they don’t break in the first year when being used to the full potential, then hopefully they should carry on for the rest of their natural lives, whatever that may be (degradation aside).

I don’t think I would have noticed at all if they hadn’t introduced the higher export rate, which induced full speed charges and full speed export, as opposed to just charging from solar. They would probably just be chugging along and I wouldn’t really know.

Anyone had any battery warranty replacement experience with GivEnergy after year one?

What happened?

If not many people reply then I guess we should take that as a good sign. Otherwise we’ll be enlightened further. Good or bad.

 

[GlynG]

Without a spreadsheet logging everything its impossible to really say with any accuracy just what the savings are - especially as the price per Kwhr has risen, dropped and bi monthly changes - a spreadsheet tracks all of that.
I hate the way the sneaky energy companies use slight of hand to manipulate their charges per Kwhr to sound a better deal then raise the standing charges, My dual fuel standing charges are £330 per year - for absolutely SFA.
They always used to say the daily charge was for the maintenance of the meter, the safety checks and meter readings - however - that was a big lie - the meter readers were only sent to check two things - 1- you hadn't interfered with or bypassed the meter. 2- you were providing them with accurate readings. Both of which are perfectly reasonable to do - so why invent a range of other reasons - why is honesty so hard to do?
None of the meter readers were CORGIE or Gas Safe trained or part P qualified - so they were not competent to conduct a safety check of the meters.

I had solar towards the end of the FIT and battery storage was pretty new to have, especially LI batts rather than lead acid, I had to make a choice, Powerwall was not available at that time in the UK.
I was screwed even though what i have is working fine after 5 years and to be honest I've not noticed any battery degradation - it seems to last as long as it ever did.
The Solax triple power batteries came in two sizes, 4.5 and 6.4 with a max of 4 batteries, probably because of price I had one 4.5 and just a couple of months later added the other two - I wanted three more but between me purchasing and my seeking the additional batteries Solax revised their spec and said because of voltage issues 3 batteries was the max. Though they sort of evaded taking responsibility for a potential mis selling issue by declaring they always said 4 batts are possible - but only for three phase - and i couldn't prove otherwise.
I did decide to sell all three 4.5 and get the 6.4s - but then discovered Solax had introduced the Gen 2 range and my batts were now Gen 1 and they weren't interchangeable and a new BMS gen two would be needed - so i just accepted I had what i had and will keep until they die - and go for something else at that point.
Having said all of that Solax have been very good otherwise with their customer service, always eager to help and assist - sometimes in life you have to choose which battles to fight and which ones to live with.

Anyway, I do charge my car from solar - once my home batteries are full, In the summer my batts are fully charged by 10.00hrs so i plug the granny charger in and make sure nothing from the grid is used to charge it, as long as solar is generating over 2.5Kw then i know the house load and the car will be covered by solar, nil from the grid and nil from the batteries. of course i also log in the spreadsheet all the KWhrs that the car has consumed and that factors into the overall savings solar provides.

I've avoided smart meters too, think they are a scam, and they save nothing at all for the consumer but plenty for the energy companies - all they can do is frighten people into turning stuff off and that's how they save. Now you can only save once - once you get indoctrinated into the minutia and paranoia of turning things off it conditions people into a miserly life - and to me adding purgatory to life isn't an option, I also believe economising doesn't help anyone in the long term, If you save money each month by turning stuff off it also likely you apply that thought process to other things like going cold to save gas, buying cheapo stuff from the supermarket or changing the supermarket you shop at - and when you've done all these things there is no further prospect of saving - you've done it all.
Every business wants to earn more each year - if profits go down they will simply increase the price of the cost per Kwhr to recover that - so the customer eventually just pays more for using a lot less.
I know the end result will be i have to have a smart meter because they will get me on the safety checks, they will declare my meter is beyond its service life and the only meters now made are smart, once we all have smart meters they will introduce variable charging, so peak demand times we will pay more, so if i want to eat at "normal" times i will pay more - and also when this comes my spreadsheet is completely buggered up - no way to measure the savings even though the savings wont disappear.

There is one good thing with a smart meter and that is when excess solar is exported and saved with grid storage and when the sun goes down the electricity you use is what you previously exported - No need for home batteries at all then.

 

[Js1977]

 

[Mrklaw]

What’s the difference between

- don’t charge overnight but fill up with solar, then export excess

- charge overnight to full then export all solar

Aren’t both effectively giving you a full cycle during the day regardless?

 

[Steerpike]

What’s the difference between

- don’t charge overnight but fill up with solar, then export excess

- charge overnight to full then export all solar

Aren’t both effectively giving you a full cycle during the day regardless?

The first option runs the risk of using peak electricity if the battery is not charged sufficiently during the day to last until off peak.
The risk varies according to time of year and weather.

 

[KennethS]

You're technically correct here, but you need to look a bit deeper into how Giv do their warrenties. https://midsummerwholesale.co.uk/pdfs/giv-battery-warranty-2022-v3.pdf

Warranty is effectively a discount on a replacement battery. The discount on a replacement battery reduces with the age of the battery and further if you've had excessive cycles. (Basically they're saying you should expect a 10 year life on the battery)

If your battery dies at 8 years, you get a 15% discount on a replacement.
Even on unlimited cycle warranties, that's further reduced if you're above about 1.3 cycles per day "fair use". With the capacity limited batteries (2.6/5.2kWh batteries) it's just a cliff-edge maximum number of cycles before warrenty expires.

Odds are if the capacity reduces below 70%, your battery will be old and with higher than "fair use" cycles, which means the capacity warranty is effectively worthless.

In any case, with the warranty policy as it is today, excessive use of the battery isn't free of drawbacks. That said, I think you're probably safe charging up overnight off peak and discharging over the day

Is this the way other battery warranties work or is the warranty a factor to consider when choosing a battery setup? I genuinely didn’t dig deep into the fine print when we had our initial Powerwall installed (although back then the choices were far more limited).

 

[Js1977]

Is this the way other battery warranties work or is the warranty a factor to consider when choosing a battery setup?

I would honestly say that I would/did look at the warranties when I purchased. ROI maybe not so much (but it did work out at 10 year worst case scenario).

For me, It was like buying a 10 year insurance insurance policy on my electricity that I either paid now or paid by then and have absolutely nothing to show for it.

The panels and inverters having a 25 year warranty was just the cherry on the cake even though I feel it might be to good to be true. Time will tell.