Perplexed.Do i really need to change battery after 10 years?

mmistroni

HI all
 i am really confused from this article. 
Solar panel benefit seems obvious to me...  Even if it takes 10 years to recoup the cost of initial investment, after that my electricity bill will be mostly paid for the rest of my life?
But if i have to spend 5k every 15 years to replace battery, then the whole thing  is  not really cost efficient--- with 30-35 more years of life expectancy i will end up spending 20k in solar panels and i wont really get any benefits?
I live in a 2bed terrace house, my average electricity consumption is 2.7kw / year, i dont own an EV and due to my house setup i wont be able to install an EV charger outside my house
Based on my average calculations, between march/septembery i wont spend anything on electricity and the export i will do  will help pay for usage for october-february
Could anyone how has already having panels for quite a while (> 5 years) share some advices?
Thanks in advance and regards
 Marco

Screwdriva

Batteries typically make financial sense when household consumption is above average (well north of 4000kWh a year). There are other reasons to invest in batteries (protection from blackouts being a primary one)

We are a low consumption household without a battery (PV only). We export our excess Solar to the grid and have not paid for any gas/ electric since 4/2022. 

35har1old

mmistroni said:

HI all
 i am really confused from this article. 
Solar panel benefit seems obvious to me...  Even if it takes 10 years to recoup the cost of initial investment, after that my electricity bill will be mostly paid for the rest of my life?
But if i have to spend 5k every 15 years to replace battery, then the whole thing  is  not really cost efficient--- with 30-35 more years of life expectancy i will end up spending 20k in solar panels and i wont really get any benefits?
I live in a 2bed terrace house, my average electricity consumption is 2.7kw / year, i dont own an EV and due to my house setup i wont be able to install an EV charger outside my house
Based on my average calculations, between march/septembery i wont spend anything on electricity and the export i will do  will help pay for usage for october-february
Could anyone how has already having panels for quite a while (> 5 years) share some advices?
Thanks in advance and regards
 Marco

What's the lifespan of a panel?
Do they not loose there efficiency over time?

Screwdriva

35har1old said:

What's the lifespan of a panel?
Do they not loose there efficiency over time?

Around twice that of a battery if not more. And there is discussion ongoing on how little efficiency is lost on older panels.

Martyn1981

35har1old said:

mmistroni said:

HI all
 i am really confused from this article. 
Solar panel benefit seems obvious to me...  Even if it takes 10 years to recoup the cost of initial investment, after that my electricity bill will be mostly paid for the rest of my life?
But if i have to spend 5k every 15 years to replace battery, then the whole thing  is  not really cost efficient--- with 30-35 more years of life expectancy i will end up spending 20k in solar panels and i wont really get any benefits?
I live in a 2bed terrace house, my average electricity consumption is 2.7kw / year, i dont own an EV and due to my house setup i wont be able to install an EV charger outside my house
Based on my average calculations, between march/septembery i wont spend anything on electricity and the export i will do  will help pay for usage for october-february
Could anyone how has already having panels for quite a while (> 5 years) share some advices?
Thanks in advance and regards
 Marco

What's the lifespan of a panel?
Do they not loose there efficiency over time?

Supposedly, but the UK is gentle on solar panels (translates to poor generation compared to very sunny climes). After 13yrs, I haven't noticed any significant drop in performance with my panels. I was expecting 1% to 2% per annum, but it must be less than ~3% (total), or I'd start to see a trend in my generation figures.

Perhaps tempting fate, but looks like degradation is insignificant.

thevilla

I wouldn't expect a battery in 15 years to cost the same as now and I'd expect significant performance improvements.  Home storage hasn't really been around for 15 years has it?

Solarchaser

Short answer to your question, do you have to replace every 10 years?
No.

Longer answer, there is no large wealth of people who have had batteries for 10 years who can confirm or deny exactly how long they will "last"

I've had batteries for 7 years and the degradation in them being cycled to 10% each day is/was between 8 and 0% depending on the battery management service that you believe.
So they either had 100% at best estimate, or 92% at worst estimate.

I did replace them, (well technically I still have 3 of the 9) but that was due to my wanting to increase the amount of storage, and the cost of batteries decreasing significantly in the last year.
This meant I was able to go from 20kwh to 60kwh of storage for the same price I paid 7 years ago.

I've always worked on the premise that over 4Mwh per year of usage means batteries will make sense, and under that, it's pretty borderline.

However a couple of things have happened in the last year or so in the  ever changing energy market to change that.
First, octopus energy started offering 15p per kwh of export to anyone with solar panels.
At the same time, if you had a compatible EV for their intelligent tarriff, you could then buy energy overnight at 7p for 6 hours, and essentially sell it back during the day at 15p. 
This was a game changer for those of us with a compatible EV, but still limiting for those without one.

However recently Eon have released a tarriff to owners of EV's or BATTERY SYSTEMS that allows you to charge at 6.7p for 7 hours and export at 16.5p.

Some basic calculations. 
If you were to buy a system capable of storing 12kwh, then you could charge every night at 6.7p for 365 nights =£294

There is an accepted rough estimate of 20% round trip losses, though most systems are more efficient than this, it gives a good round number for conservative figures.
So 0.8x 12 = 0.96kwh
0.96kwh discharging during the day at 16.5p over 365 day =£578
A pretty straightforward profit of £284

So over 10 years that would be a profit of £2840.
Double the battery storage and you double the profit.

These are the batteries I've been running over a year with zero issues
https://www.fogstar.co.uk/products/seplos-mason-280l-and-x16-grade-b-envision-305ah-battery-bundle?srsltid=AfmBOoqBQtQ1VOxXLtf0iDLvnhfcNddVo2KgjN5eYiTswnuHPJHmg9pv
I bought them at £2000 each, they are now down around £1400

You would need an inverter to run them obviously,  but that should be very easily findable for under £1k

So a £2400 outlay could bring you back £2840 over 10 years, and a £3800 outlay (double the batteries,  but same inverter) could bring you back £5680 over 10 years.

And all of these calculations don't take into account the fact your batteries if not exporting at 16.5p, are instead stopping you buying electricity at 20p +/kwh

My own, I set to force discharge at the times my house would normally use the most electricity,  which tends to be when the grid is dirtiest anyway, so it's a small contribution to greener energy also.

If you then had to replace the batteries in 10 years, I'd expect them to be cheaper again, or really if they have degraded by even 20%, you could still use them at reduced capacity,  no need to throw them out.

Martyn1981

Hi Solarchaser, price reductions must be a dilemma now. I was thinking with cheap(ish) batteries we could install 110% of need, so batteries are run a bit more gently, but if they've lost 10% in 10yrs, you still have the required capacity anyway.

Or, with falling prices, just expand over time, as you mention.

You're 4MWh idea is a good metric. Perhaps not too long before batts just become an easy choice for more people as prices fall.

2nd_time_buyer

Solarchaser said:

...

These are the batteries I've been running over a year with zero issues
https://www.fogstar.co.uk/products/seplos-mason-280l-and-x16-grade-b-envision-305ah-battery-bundle?srsltid=AfmBOoqBQtQ1VOxXLtf0iDLvnhfcNddVo2KgjN5eYiTswnuHPJHmg9pv
I bought them at £2000 each, they are now down around £1400

Really useful knowledge there, thanks. How easy is it to find someone to fit those? The nearest Fogstar installer is 50 miles from me and said I was too far. Do you think a general electrician be able to install or an installer for other systems?

Heedtheadvice

It ought to be very easy for a qualified electrician who is familiar with both batteries and inverters. 

You can find electricians from https://www.renewableenergyhub.co.uk/.

Not suggesting any you find there will be any good or cheap but if you post your general area you might get better suggestions.

It makes sense to use the same electricians as are installing your solar for continuity and hopefully cost saving. Apart from good electrical trade registration and training they should also be MCS registered ( required for necessary approved installation) and ensure that the Distribution Network Operator (DNO) requirements are met - be that by informing them for basic installs or the higher power approval.

Having said that I bet some have been naughty and done a DIY job ... but I really ought not comment on them.....

I must add that batteries are quite heavy in the order of 20Kg per 2kWh. So handling them is not for everyone and siting them needs to be planned. 

(Solarchasers 60kWh set are probably heading to antipodean locations :-) 😀 )

Solarchaser

Hi Mart, yeah the price drops are great if you haven't bought, but suck when you have.
I could have saved myself over £2k if I'd waited a year.... I'd never have waited a year though 😁

2nd time buyer, that's a good question, and i don't know is the honest answer, I'm a person who likes to mess about with stuff and is fairly handy, so I don't tend to like paying for someone to do something I can do myself. 

Personally I looked at a couple of videos of assembly on you tube and thought, yeah I'll give it a go, but if you haven't messed about with stuff like I have, you would be naturally reluctant to DIY and so the cost of the batteries would in fact increase.

Fogstar do pre-assembled batteries for i think another £200 and I'd expect any electrician who even half knows his stuff to be able to wire it up to an inverter. 

Heedtheadvice yeah I think you are about right with the 2kwh for 20kg on the Pylons.
The fogstar I think are about 110kg for 15kwh, so a little less, but still, not something you would like to fall on your toes.

I was lucky that we have an extension, and so I was able to bolt some homemade brackets onto the old brick wall, and they take 3/4 of the 60kwh, the other 1/4 just sits between 2 joists on the loft floor



A pic of 2 full sets and one half set (to the right) as I took the pic while still assembling