Reply With QuoteDon’t they also have a life span, so after waiting years to recoup your money you end up having to replace them and the cycle starts again.
So I'm looking into getting solar panels but... how do I know as a novice that the gear they suggest is "good" (amongst the various options on the market) or assess the realism of the payback periods?
Don’t they also have a life span, so after waiting years to recoup your money you end up having to replace them and the cycle starts again.
The inverters are the thing to take care with.
Neighbour had a system installed last summer for £11k all in. About half of that was for the pair of big batteries for power storage.
Not sure what he thought the clawback period was, but he is probably looking towards the time when he might fit a heatpump.
Are solar panels still viable then? We’re moving house soon and looking at panels as an option but I don’t know anyone with them to talk to about viability, payback, etc
I think they’re only viable if fitted along with battery storage and the ability to sell the power back to the grid. The best use case I’ve seen is the Tesla Powerwall and solar panels.
Solar panels on their own have never really been worth it in the long run. Especially if you factor in the environmental impact of production and disposal.
People seem to think that 8 panels on their roof will power the whole house, but the reality is that 8 panels can barely power the fridge.
After much research we have decided to sack this off. Current best guess for pay back for our best installation was 9 years.
When you look long into an abyss, the abyss looks long into you.........
Dubious payback at best. Don’t believe promotional material, and do your own maths.Originally Posted by Alansmithee
Daytime leccy prices are 28p/kWh and nighttime <10p/kWh. First thing you should do is get one of these tariffs and put everything on night time rates; EV, tumble dryer, washing machines, dishwasher etc. Basically everything you can.
I have done this a 80% of my leccy is used at <10p/kWh. Payback now on solar is multi decade for me.
Plus when the sun is shining is not necessarily when you want to use leccy. So, you sell it back to the grid at a bit of a pittance. Otherwise you need solar plus batteries and now you are up to £20k for a decent system.
I found solar to be a complete con. Plus you have all the black crap on your roof.
Just be smart and buy and use your leccy at the cheapest rate possible.
How much was the quote Chris for what size system, did it include batteries
Hope he doesn’t mind me quoting him, but this was from the air source heat pump thread a week or two ago. This was installed cost as he had solar and batteries fitted.
This guy had 14 PE panels between two roofs, one thermal panel on a roof, and 6 thermal panels between two walls! Looked lovely!
We had a quote 6 or so months ago...fitting as may panels as we could, appropriate number of batteries and inverters etc. Using some slightly more conservative assumptions than the salesman who quoted for them I came up with a realistic 8 year payback which doesn't make a lot of sense in my mind.
We were also told that the panels and batteries wouldn't work during power cuts. We get them fairly often and having a backup power supply would have been a strong selling point but it would seem not, at least not with the system he was proposing to install.
Will dig it out - from memory this was 14 panels and storage batteries - just shy of £12k installed.
EDIT - just found it:-
18 panels
5kw battery storage
£13.5k
Last edited by Chris_in_the_UK; 3rd April 2024 at 19:21.
When you look long into an abyss, the abyss looks long into you.........
Ive just checked the data on my inverter, we moved in to this house new back in 2019 but the install was done June 18. We've had very little generation since January so the generation to this point is 11500 kw. Works out at roughly 2300 kw generated a year (small array 2.4kw) If you had 14 panels I'm assuming they were 400w so you'd have a 5.6kw array which is double mine. You would be looking at 5kw generation a year easily with the system you were quote.
Surely you're break even point would be quicker than 9 years?
18 panels - 7.2kw. Almost triple mine.
One of the issues we have is (self-inflicted) we have an electric AGA and an installed hot tub. Just re-checked the pages of bumf and their estimated payback point was 8 years (quote was from late 2022).
Obviously beyond year 8 we are then starting to benefit but I am struggling with the principle of paying out that kind of money = I know, first world problem....
When you look long into an abyss, the abyss looks long into you.........
All personal preference really, something that pays for itself in 8yrs and then continues to save you money for years after that seems a pretty good idea to me.
The right system definitely works during power cuts too.
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That is beyond offensive.This guy had 14 PE panels between two roofs, one thermal panel on a roof, and 6 thermal panels between two walls! Looked lovely!
It may not work for everyone, YMMV etc, but a number of the points you make here are questionable.
When the sun is shining might not be when you want to use electricity? Nor is the middle of the night! Charging the EV overnight obviously makes sense but less so for cooking the Sunday roast!
Selling excess back to the grid at a pittance? I sell it back at twice what I pay for it!
As for the 'black crap on your roof', I think we've covered that elsewhere...
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Fine if you are having to pay 30p/kWh to charge you EV, for example. I mention EV as they are the highest domestic demand by a country mile if you have one of those cars.
But, most people are paying pennies to charge their EV, and on that basis, and by my calculations my payback period was around 30 years for a £20k solar/battery installation.
Twice of not a lot is not a lot. Buy at 10p, sell mostly at 20p?
Even if you have 10kW battery pack, that is only £1 per day, and a 10kW pack costs £10k.
Got you, yeh you have some energy munchers right there.
Tesla Powerwall 2 is 13.5kw and is under £9k now.
Plenty of excess that's not been bought at all in the summer too.
Last edited by gunner; 3rd April 2024 at 20:45.
Going to revisit and get some up to date quotes.
When you look long into an abyss, the abyss looks long into you.........
I am not that interested in becoming a domestic electricity trader.
Even at £9k for 13.5kW the payback is far too long for electricity arbitrage, even if I was interested.
I am fine with solar and batteries if you can get a half decent payback. I just can’t, and can’t get anywhere near a decent payback, mainly because electricity is so cheap overnight for charging the EV (also using tumble dryer, washing machine and dishwasher) which seems to be the lions share of my overall electricity usage.
If you are an extremely heavy user of daytime electricity, then I am sure you can get the economic to work. Most people aren’t, and anyone with an EV charges for pennies overnight.
We have a double oven gas cooker for cooking Sunday lunch :)
Tbh i was surprised what my generation was with my small array, i have considered adding more because we have the room and adding a battery, think id be looking at c6k. There are some very good batteries coming through now vastly cheaper than a few years ago, plus you don't have the VAT on the batteries anymore which makes them cheaper. My issue is that we’re planning on downsizing somewhen between now and when i retire so around 6 years. I guess it also depends how long you intend to stay where you are Chris.
Given the amount of money we have spent on the extension/refurb I doubt we will ever move now = never say never, but unlikely.
I am going to get some new quotes with/without battery storage.
When you look long into an abyss, the abyss looks long into you.........
I don’t mind at all. That cost included 3.5K of roof costs by the way, as they are in built panels and we needed the ridge sorting anyway. The maths stand up, given our use during the day.
I would still do again, we went with a solar edge system (recommended by a friend who is a fitter). These are most of the panels (another 2 on a different roof), strange layout as we are having a porch put in the corner.
If you are on a tariff like Octopus agile, there is probably more to be gained by having just a battery (and little or no solar). Use cheap leccy to do the major tasks and top up the battery overnight, then sell the leccy back into the grid at peak times from the battery.
We have put solar on the roof of a property in Devon, but it has a large south facing roof (that needed replacing) and a higher seasonal load when the sun is shining, so it makes sense.
Our installers there said that most of their most recent work had been installing batteries, so that people can farm the difference between the cheap and expensive rates.
Let’s say you get a 13.5 kW power wall installed for £9k and you set a minimum of an 8 year payback. Just battery and no solar.
8 x 365 days = 2,920 days each 13.5 kW, therefore 39,420 kW over 8 years. Assumes full charge and discharge once per day for overnight/daytime rate arbitrage.
13.5kW is highly optimistic given a battery’s useful output will not be the full amount quoted, just like an EV battery.
So you have spent 900,000p to get 39,420 kW, or each kW needs to be valued at a buy/sell spread of 22.8p.
The typical spread between buying cheaply overnight (~10p/kWh) and selling at a better rate in the day (~20p/kWh) is 10p/kW. Better to use all the electricity yourself in the daytime if you can.
So, no chance of breaking even after 8 years.
More like 8 x 22.8 / 10 = 18 year payback.
Battery system will be dead in 15 years.
I leave electricity trading to the big boys. And there is a reason they don’t use batteries. Energy density is very poor and capital cost is very expensive.
I’d also prefer the risk of running a washing machine overnight compared to a large volume of batteries constantly cycling in the house.
I have 69 kWh of paid for battery in my car. More sensible to somehow use and trade that, than adding domestic batteries in the house.
Last edited by noTAGlove; 3rd April 2024 at 22:26.
We get that you don’t want to do it, but it still doesn’t mean it doesn’t work for anyone.
If you use the cheap overnight electricity at peak times the arbitrage is much bigger.
I agree. But when you stump up your £9k capital cost (or whatever it is), there is no contractual returns for the lifetime of the facility.
Buy/sell spread may be fine for the first few months, few years, or decade. Or the buy/sell spread may cave in just after you have laid out your investment. And it is now an investment.
As mentioned I have no ambitions to be a spot market electricity arbitrage trader.
Yes, it’s a fixed cost now against a variable return in the future.
My guess is that electricity costs will go up rather than down, which is why I’m happy using capital (while I’m earning) to install solar and batteries and reduce my costs in the future. It doesn’t have to be a buy/sell spread arbitrage.
Horses for courses.
Last edited by gunner; 3rd April 2024 at 22:52.
Solar opens up other tech that you wouldn't ordinarily access, it’s been mentioned on here before but if you have an immersion theres devices that will divert excess directly to your immersion heater. My iboost was installed in Feb 22 at a cost of £300, data directly from the unit tells me it’s diverted 1450kw which is roughly £435. Im £135 up in a little over 2 years. It’s there just doing its thing without any intervention from me.
I think you are right. Cheap wind farms have been done, and what is left is more expensive to develop in deeper water.
Carbon capture and storage on the back of gas turbine ain’t cheap, and gas now has to be sourced as LNG in part. New nuclear is horrifically expensive.
Doesn’t mean the day/night spread is guaranteed to widen, but I agree with you we are going to be paying more for our electricity in the coming years.
Exactly, the buy/sell spread may not widen but the generate/buy spread would.
As long as your immersion needs a boost during the day, because if not, it is only displacing cheap overnight electricity.
When I did my investigations, I found that you have to be very careful with the scenario and maths, but great if you have done your homework and it all works for you.
As previously mentioned those with large electricity demand in the daytime will benefit the most.
I was using 80% of my electricity in the daytime until recently and I am sure solar/battery may have benefited me.
But, now only use 20% of my electricity in the daytime and it just doesn’t work.
My recommendation is first shift what you can to overnight use, and then undertake the economics on that basis.
They would have to, because a 10p/kWh spread (with the occasional improvement) is not enough to payback £10-20k of capital investment as discussed above.
Plus, who knows. Overnight demand must be set to skyrocket as EVs become more prevalent. It could mean overnight rates become proportionately more expensive because of supply/demand.
A lot of speculation, but hope it pays off for you over the finite lifetime of your equipment.
For anyone considering the investment all I can say is do you research very carefully and ignore the promotional bumf.
This thread has kind of demonstrated that it’s very difficult to do your own research simply because it’s very difficult to work out what your annual generation will be. You can work on the scenario of 6-7 reasonably good months and 5 rather poor months but thats it. Thats all you’ve got other than tapping on your neighbours door who has solar and asking them how much they've produced…assuming they have that info.
Tbh if i didn't have solar and was considering it, i knew i was going to be living in my property for at least the next 10 years, i wouldn't look at solar particularly as an investment and be too worried about the break even point.
It’s very individual to your property and location as said before. Our system as an example generated 183kwh in Jan, 205kwh in February, that jumped to 450kwh in March, and in the first 3 days of April it’s 54kwh. This is despite the rubbish weather we have had.
As a busy family of 4 we cannot move our use to night time, we have an EV but don’t do many miles as my wife and kids walk to school/work and I work from home or get a train to the office. NoTagLove is very negative about solar, I assume that’s based on his lifestyle/prejudice against the technology. We cannot cook meals in the middle of the night, need to run appliances in the day. and I use electric heating in my garden office too. So it makes sense for us.
My old friend is a solar installer and helped with the calculations based on our usage, our payback should be 6.5 years at current prices. Also warranties on batteries and panels are a lot better now (from memory it’s 10 years on our battery and inverter and 15 on the panels).
Just look at the agile prices to see the spread. You can buy late night/early morning at 8p/kWhr, and sell at high 20s, at least 27 (some periods are over 30) at peak time in the early evening. That means a spread of 19 p/kWhr. That alone about halves the payback calculated above (which I won't bother quoting again).
The reason the big boys don't do batteries is that a massive battery system is not sensible, as it needs hefty distribution (and inverters) to/from it which is a large investment on top of the battery.
That is why Octopus have started agile, to encourage distributed storage, which needs no infrasructure upgrade to make it work as the generated power is used locally.
And I can assure you that some people do make it work.
There is also a very strong argument that autonomy (which does need solar, not just a battery, but a battery is one way of making better use of the overgeneration overnight) is the right way forward.
And ANY forward progress is the right thing to do.
This can be viewed in an investment in the future, rather than just another investment that needs a commercial rate of payback to be sensible.
You have me completely wrong here. I am not negative about solar or batteries, I am dubious/negative about any product were the marketing and promotional information is geared to an upside case, and may be complete guff for many who have not first tackled the easy wins, or not willing to put significant effort into understanding a relatively complex mathematical problem with added uncertainties and risk.
Before investing in solar/batteries you should tackle the 'low hanging fruit'. This includes low cost energy efficiency changes, and switching to energy efficiency appliances on natural replacement.
You can now get fixed 8p/kW hour (as opposed to 28p/kWh daytime rate) for 12am-7am every day of the year (e.g. E.ON Next Drive). That is a duration of 30% of the every day of the year. If you can, switch your EV, immersion heater, tumble dryer, washing machine, dishwasher to those hours. It is just incredible how much bulk energy you can consume overnight at 72% less unit cost.
Once you have completed the above, track your usage and allocate it to the higher 28p rate and lower 8p rate, and then calculate your new annual energy cost.
Calculate your 28p/8p energy savings with solar/batteries, and compare it with your significant capital outlay to calculate a payback in number of years. Decide on what payback is acceptable for you. Recognise all your capital is fixed and the savings are at the mercy of the market going forward, and that is an inherent risk you have accepted.
Also accept that you are now a spot electricity market arbitrage trader and that comes with a certain level of risks. Weigh up your calculated payback with these additional risks and uncertainties.
This is quite a significant investment in time and effort to get the the optimum answer, and many people are not up to the level of rigour and can easily get sucked in by promotional guff.
Bottom line is do your homework properly.
I think you are. Several people have made quite valid cases for both but you continue to refute their use cases.
We're all taking a view on energy prices, whether we like it or not. A pejorative description of others as 'spot traders' isn't helpful. If you decide not to become more energy independent, you are also making a call on being happy with whatever is on offer in the future.
Evidence of the point above, this is a current offer, not necessarily available in the future so not a great basis for an argument.
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The level of ignorance and misinformation on TZ-UK is generally quite low but this thread is the opposite. The posts by gunner are in my experience highly accurate and true - some of the posts disagreeing with him are not and some fall into the category of being ignorant and/or spreading misinformation.
In terms of the original questions posed by alansmithee, I would check on references for the installer in terms of quality of work. In terms of the generation figures then make sure you are using an accredited installer as they belong to MCS asthey use a standard validated method for calculating solar panel output and system capacity. Panels do indeed have a lifetime but the part most likely to age first is the inverter.
Typically they have a 10 year lifetime, panels tend to have a longer lifetime particularly modern ones. Like most things the tech has improved and continues to improve. Roof orientation is key - a south facing roof at a good angle is best. You also need not to be shaded by trees. South West and South East installations will also work but your panel output will be lower. Inverters are a key element of the system - there are various makes - I went with SolarEdge which is rated as one of the best for output and reliability. The inverter regulates the power supply to each panel to obtain the maximum output and then converts the DC panel output to AC output.
Battery wise there are many choices but you also need an interface beween your solar installation, battery installation, house load and the grid. This interface is often referred to as a gateway. Tesla provide such a gateway as do others. It allows seamless switching between solar, battery and grid and balancing all these power soruces and users. It fully supports grid outages ifyou connect the Tesla gateway to Tesla Powerwall.
I have a 6.6kw array (18panels) which has been installed exactly a year tomorrow. It has generated in that year 6.35Mwh which is higher than the estimated output of 6Mwh. I have two Tesla Powerwall 2 attached to the Tesla Home Gateway each has 13.5 kw. The cost of the each Tesla Powerwall 2 was £6.5k. Peak daily solar output is around 45kwh.
The battery capacity is enough to run the house for around 1.5 days. I use Octopus Intelligent Go and since having the system with two batteries all my grid electric usage is at 7.5p per kwh. Excess solar electric is sold back to Octopus at 15p/kwh. TheTesla Home gateway hasa number of inbuilt algorothms to cater for different scenarios- you can tailor these algorithms. During the winter months, I allow the powerwalls to charge up from the grid during the 23.30 to 05:30 7.5p/kwh period. During sunnier months, I switch back to the self powered algorithm where solar provides enough power to run the house, charge the batteries and sell excess solar back to the grid.
Switching things like washing machines,tumble dryers and dishwashers to use cheaper rate electricity does indeed help to cut costs but some things cannot be easily switched. E.g. microwaves,electric cooking kitchen appliances, kettles, toasters, coffee machines,fridge freezers, central heating,etc. Be wary of going onto an Agile tariff as in my experience when compared to Octopus Intelligent Go you have to be very much an edge case consumer to benefit.
Last edited by chris56; 5th April 2024 at 05:51.
Post your maths, like I have posted the analysis above.
Funny how those are claiming spread of misinformation and not one of the solar users has posted any lifetime figures, just anecdotal snippets and qualitative comments which count for nothing.
At least I post hard numbers and hard analysis to back my stance up.
I find you all very defensive and touchy, which is probably because you are being challenged about the rationale of your investment.
My average cost of electricity is 15p/kWh (6.2p/kWh more than yours), and I haven’t lumped in up to £20k capital to achieve that. It cost me zero. Nada. Nothing.
I am sorry but if you can just use/buy a good chunk of your energy overnight (for example to charge your EV) like you do for 8.8p/kWh or less, there is no way you can ever break even in a reasonable time when selling back at 15p/kWh. A 6.2p/kWh buy/sell spread is shockingly bad.
Everything is smoke and mirrors from you solar/battery users if you are not willing to post up your capital and multi year usage and costs.
Lots of snippets of information which all adds up to tell you precisely nothing. No details of capital outlay and annual savings. No details of what can be achieved by just switching to a cheap overnight plan. Smoke and mirrors. And you complain about misinformation.
It’s very difficult to actually give a figure hence the reason for the post.
All I will say is that since install my system has generated 11500 kw of energy. My house has benefited because it has in most cases powered it throughout the day and taken most of my base load.
I need to heat the water during the day because we have showers in the evening (4 of us) and so there is no choice. I could load shift to an over night tariff but I’m already on Agile which is cheap anyway
I have no need to charge my car over night or during the day but will attach it up if there are free sessions going. Apart from that I charge at work.
My immersion through the summer months is powered almost exclusively by the sun as it’s always up to temperature and the timed boost hardly ever occurs.
Whatever I don’t use gets sold back and I can see as much as £15 a month off my bill due to that. I have a small array, if I had more I would benefit more. I was lucky as the house was installed with solar when moved in so I’m not always trying to work out what’s it’s saved me with regards to break even.
Despite NTL reticence I’m sure he would benefit long term, clearly he thinks he doesn’t, some of us that have solar think he will. It’s his call… who gives a shit?
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Your version of 'hard numbers and hard analysis':
Actual facts from one of the anecdotal, smoke and mirrors brigade:
Still just numbers. No financial analysis.
After all that is usually the first thing people want to understand, including presumably the Op.
My advice still stands.
1. Switch what you can to overnight usage. You don’t need £20k of investment to get 9p/kWh, least for 30% of the day
2. If you are a very heavy daytime user then solar/batteries may work for you.
3. If you can shift significant electricity to overnight use and get a cheap overnight tariff then forget spending up to £20k on solar/batteries. Unless, see point 4.
4. You can achieve a buy/sell arbitrage spread of at least 20p/kWh between overnight and day rates.
Everyone is unique. The above are MY broad rules, and you can do with them as you wish.
But the most important recommendation is;
5. Do you homework properly. One size does not fit all.
This is nothing new to what I have said throughout this thread, and I struggle to see any misinformation.
Good luck Op. if you haven’t spent a couple of hours with an excel spreadsheet, then you haven’t done enough homework.
First off no way am I running DW, WM or dryer while I’m asleep.
Wholesale PW2 is circa 5k, Solar thread on PH.
I have 14 panels (eurener) Solis inverter & Puredrive battery £9k.
Like others with Solar the system springs into life once the suns out & Feb was decent but March came alive.
By midday today battery was full, 3 loads of washing, Heatpump dryer on ( don’t ask mrs likes fluffy towels).
Afternoon Eddi gives a full tank of HW, dishwasher load done & exporting at 20p/KWh anything unused.
I had mine installed two years ago when bank rates were shocking & I wanted to do my bit for going green.
If I moved I would definitely do it again, but probably part of a larger eco home with heat pump, ufh, Mechanical Heat Recovery Ventilation, air con etc.
Last edited by g40steve; 5th April 2024 at 19:33.
But you’d put a bank of huge lithium ion batteries constantly cycling somewhere in, or around your home while you are counting sheep? Err, OK.
How do you feel about the fridge/freezer?Do you turn the fridge/freezer dual compressor off overnight? If not, you clearly trust the fridge/freezer!
What about the immersion heater, or the gas boiler that comes on in the wee small hours to heat your water or warm the house?
As for the TD, clean out the lint after every cycle. Latest RCD trips and numerous smoke alarms on every floor is standard in our house whether we use appliances overnight, or not.
Have you seen what happens when a fire takes hold of li-ion batteries? A garden hose will not get you very far.
Last edited by noTAGlove; 5th April 2024 at 20:09.
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