Solar panels: do they save money?

[Dabop]

We could profitably have a wind turbine. A 3.5KW plumbed into the mains would be about £25K installed. Excess production locally limits me to 3.5 down from 5 originally. Plus an annual service plus insurance with it being within quite a long way of a road/house for when the blades fly off.
The turbine itself only costs something like £5K, or did at the time.
Instead of FIT and grid connections I wonder if there is a future in each property having its own production and storage?
Any"renewable" grid connection requires a duplication in capacity for when the wind/sun is being cheeky because demand doesn't take that cheekyness into account.
As some on this thread have said, it is perfectly possible if you know it's going to be sunny you put the washing on, because you profit from your installation. Individual decision making is possible.
A lead acid battery bank in your shed (communal?) of a size to run a washing machine, charged from your own turbine and or solar panels could be a scalable kit installed by a nationwide govt sponsored contractor. You in control of your supply in a limited way, no profit directly just savings as life goes on ever more expensively. The house remaining on grid as now, just a mains battery sourced supply for whatever you plug into it.
Not lithium of course, limited lifespan and much more expensive in a use where paying more for the weight saving is irrelevant. Lead would require perhaps more maintenance but that could be interested competent householder or a visiting techy.
Using ones shiny Tesla as a battery bank is only sensible if your wallet is deep and you shut your eyes when you watch how fast it's emptying. Such a cars lithium battery at say £10K new lasts 1000 full charge cycles. Every time the leccy company borrow some of your stored capacity you may get paid a profit on the energy cost down the cable but does it cover battery degradation?

Just to correct a few points...

L/A is obsolete and despite it being 'apparently' cheaper, in terms of actual storage versus life expectancy, is the poorest choice by far....
Say you want a '200ah' capacity (which in a 12v bank would be 2.4kwh, in a 24v bank 4.8kwh)

With lead acids- you get 300-500 cycles if taken to 50% DOD (depth of discharge)- which means you actually need (sticking with 12v here) 400ahr of 'label' ahr...
if you want 1000-1200 cycles, you have to stay under 25%DOD- but that means you are now up to 800ah of label capacity
You 'might' get 3000 cycles if you keep your DOD under 10%- but that means to get that 200ah of actual capacity, you are up to 2000ah of actual batteries required!!!!

Li-ion (as used by Tesla and in your phone- depending on quality, they can get up to 1200-1500 cycles at 80% DOD with active BMS and cooling etc- without it, 300-500 cycles is more common- they have the advantage of a lot of storage in a very light package...

The outright winner in terms cycle life is the LiFePO4- which is what is found in most 'home batteries' (except Tesla Powerwalls which currently use Li-ion)they weigh about twice as much as Li-ion per kwh, but at 80% DOD last in excess of 5000 cycles, and at 70% DOD in excess of 7000 cycles- yet cost about 2-2.5 times the price of L/A...

In terms of equal storage capacity to lifespan- a 200ah 'actual capacity' bank means you will have to oversize your L/A bank by a factor of TEN, and even then, it will only last half as long as a LiFePO4 bank- meaning that you need to buy 20 times the 'ah label' of L/A to equal the same as a LiFePO4 battery- which costs only 2.5 times the price...
This is important to understand if you actually want to use the system in reality...
(I installed offgrid systems,boats and 4wd dual battery systems since the 80's and live offgrid myself electrically, due to the cost of getting 'the mains in'- my own system cost under $18k Au, where getting the powerline run in was $42k...)
To equal my approx 200kg of LiFePO4 cells (I got 20kwh of storage at 20 years with 70% DOD) with L/A- I would need to buy close to six TONNES of L/A batteries over twenty years...
:-O

 

[hairy]

My subsequent post mentions LiFePO4 life cycles from a long standing reputable brand.
80% full is a common limit suggested for lead acid meaning five times required capacity not twenty. Weight in a house is not really an issue surely?

"(I got 20kwh of storage at 20 years with 70% DOD)" do you mean you installed LiFePO4 in 2002, or those figures are what you've been told to expect?

"it will only last half as long as a LiFePO4 bank" according to who, the lithium battery industry?

One or two lead acids in a 4x4 or camper drained pretty much flat every use running a fridge etc or in a hire scooter won't last long because they are not ideal fitments. Abused would be the word perhaps. LiFePO4 will work much better in many situations if your use justifies the much higher cost. In a house, if you side step the hype?

Thank you for your opinion though

Just to correct a few points...

L/A is obsolete and despite it being 'apparently' cheaper, in terms of actual storage versus life expectancy, is the poorest choice by far....
Say you want a '200ah' capacity (which in a 12v bank would be 2.4kwh, in a 24v bank 4.8kwh)

With lead acids- you get 300-500 cycles if taken to 50% DOD (depth of discharge)- which means you actually need (sticking with 12v here) 400ahr of 'label' ahr...
if you want 1000-1200 cycles, you have to stay under 25%DOD- but that means you are now up to 800ah of label capacity
You 'might' get 3000 cycles if you keep your DOD under 10%- but that means to get that 200ah of actual capacity, you are up to 2000ah of actual batteries required!!!!

Li-ion (as used by Tesla and in your phone- depending on quality, they can get up to 1200-1500 cycles at 80% DOD with active BMS and cooling etc- without it, 300-500 cycles is more common- they have the advantage of a lot of storage in a very light package...

The outright winner in terms cycle life is the LiFePO4- which is what is found in most 'home batteries' (except Tesla Powerwalls which currently use Li-ion)they weigh about twice as much as Li-ion per kwh, but at 80% DOD last in excess of 5000 cycles, and at 70% DOD in excess of 7000 cycles- yet cost about 2-2.5 times the price of L/A...

In terms of equal storage capacity to lifespan- a 200ah 'actual capacity' bank means you will have to oversize your L/A bank by a factor of TEN, and even then, it will only last half as long as a LiFePO4 bank- meaning that you need to buy 20 times the 'ah label' of L/A to equal the same as a LiFePO4 battery- which costs only 2.5 times the price...
This is important to understand if you actually want to use the system in reality...
(I installed offgrid systems,boats and 4wd dual battery systems since the 80's and live offgrid myself electrically, due to the cost of getting 'the mains in'- my own system cost under $18k Au, where getting the powerline run in was $42k...)
To equal my approx 200kg of LiFePO4 cells (I got 20kwh of storage at 20 years with 70% DOD) with L/A- I would need to buy close to six TONNES of L/A batteries over twenty years...
:-O

 

[Dabop]

My subsequent post mentions LiFePO4 life cycles from a long standing reputable brand.
80% full is a common limit suggested for lead acid meaning five times required capacity not twenty. Weight in a house is not really an issue surely?

"(I got 20kwh of storage at 20 years with 70% DOD)" do you mean you installed LiFePO4 in 2002, or those figures are what you've been told to expect?

"it will only last half as long as a LiFePO4 bank" according to who, the lithium battery industry?

One or two lead acids in a 4x4 or camper drained pretty much flat every use running a fridge etc or in a hire scooter won't last long because they are not ideal fitments. Abused would be the word perhaps. LiFePO4 will work much better in many situations if your use justifies the much higher cost. In a house, if you side step the hype?

Thank you for your opinion though

That's not opinion- its fact...
The brand I bought I chose for my own place because of their long term known reliability.... they have been on sale in Australia since 2008, so their longterm lifespan is a known quantity... many are already at 14 years old... (mine were bought in 2019, I know from experience however that if anything the factory cycle life is understated, I expect these to outlast me...)

I am well aware of lead acids performance levels and their limitations- having been using them in offgrid houses here in Australia since the 1980's (when they were the only practical solution) as well as in motorhomes, 4wds, boats etc...

There is no 'hype' in my comment- the limits of each of the types is a known quantity, and on purely economic grounds, the LiFePO4 wins hands down for stationary (and even many mobile) applications, lead acid 'looks' cheaper- but it isn't- by a huge amount... (the cost difference isn't even that great- 'label ah' to 'label ah' the price difference isn't that great (LYP being about 2 to 2.5 times the price of L/A) and given the huge difference in performance (in actual capacity and in service lifetime) choosing L/A is simply a bad choice...

 

[RobinBHM]

I’ve just had a thought, if global warming means more sunshine in the UK, maybe that means we should use coal fired power stations for a few years, that way solar power will be more efficient more quickly………

 

[Ollie78]

I keep considering solar with battery, this discussion is useful and its good to hear from people who actually have systems installed.
I just keep thinking that it's a shame to put holes in my perfectly good roof. Knowing my luck I would need to fix my roof one year after installing the panels !
For this reason I like the idea of the actual tiles/slates being solar so you could replace the roof in one go and get less issues with wind loading etc, it looks better etc. The price is mad for these at the moment.
I wouldn’t mind if the entire roof was made of big panels actually but not sure this is available. Seems silly to have a roof on the roof.

Ollie

 

[Sideways]

For roof replacements there are a few options. Tesla are in the early days of promoting a solar roof tile that looks about 3-4x the width of a common UK tile.
There is a system where a black plastic tray is fitted to the roof timbers in place of the usual felt + battens. Solar panels are then fitted close over that making a tidy and low profile "in roof" installation.
Lastly, and pretty new, there is a brand of panels on the market which interlock and seal along the edges so that they can be installed as an alternative roof covering without the plastic tray below.
The main drawback of the in roof system and the latter one which I think is by Viridian Solar (owned by Marley), is that the panel outputs are weak compared to the better standard panels. The "in roof" installations suffer from heat because they don't have ventilation behind (solar panels work best in the bright but cold) and the Viridian panel just isn't an especially high performance variety at present.

No doubt that the best time to install solar is when you build a house or when you need to reroof for other reasons. I'm too late for one and if I wait for the other, it'll be too late for me We're going for it. Only time will prove whether it was the right decision.

 

[Dabop]

No doubt that the best time to install solar is when you build a house or when you need to reroof for other reasons. I'm too late for one and if I wait for the other, it'll be too late for me We're going for it. Only time will prove whether it was the right decision.

In Australia, most roofs are metal, with older buildings using clay tiles (falling out of favour these days)- and rarely if ever require 'reroofing'- the Colourbond on my shed for example is guaranteed for 35 years- and there are buildings in the area that are a hundred year old 'corro iron' on them- rusty but still in use...

In fact the older clay tiles are more prone to damage from hail storms- so the panels actually protect them lol (and you would be surprised at just large the hail has to be to break a modern solar panel...)

Another factor in hot areas is that covering a good percentage of the roof actually makes the ceiling cavity cooler- which translates to cooler temperatures inside the house (at the old place, you could actually feel the areas of the roof that had panels over it when in the ceiling- noticeably cooler at those areas...)- of course this might not be a 'good thing' in some colder areas lol

Some opt for ground mounts-personally I don't like them (despite my 'tempoary array' being one lol)- they tend to get dirty faster
(my old place was roof mount- we cleaned them once in four years with a hose from the ground- after a bushfire got to within a km of the house!!!- they were covered in ash...), where my current ground mounts need a wash every few weeks because they get covered in dust...

I have seen quite a few 'double car carports' being made with only the 'skeleton frame' and no 'roof' at all- with the solar panels taking the place of the metal roof commonly used- a 5mx6m double carport could readily hold around 4.5kw of panels- of course in that case, just silicon the panel edges together, it really doesn't matter if it has a 'few leaks' being an open sided carport lol

 

[John Brown]

I’ve just had a thought, if global warming means more sunshine in the UK, maybe that means we should use coal fired power stations for a few years, that way solar power will be more efficient more quickly………

I'm not entirely sure that global warming does mean more sunshine. But I appreciate the ironic spirit of your post. Reminds me of when one of my younger cousins suggested that looking directly at the sun, around the time of the eclipse, wasn't such a bad idea, because if you went blind, it would be like me a permanent total eclipse. I think he was joking.

 

[Sideways]

These reports make interesting listening from a USA perspective

and 7 minutes in, this reinforces Dabop's point about the toughness of solar panels.


From a UK perspective it's interesting to see video of shingles being replaced after just 10-15 years vs common or garden concrete tiles used on a large proportion of UK homes which have a design life of 60 years in typical use and many last for decade(s) longer.

But our hailstones are rarely more than 3 to 4mm diameter ....

 

[Dabop]

But our hailstones are rarely more than 3 to 4mm diameter ....

This was about ten km away from where I was just before Christmas, most arrays were still intact, there was a few broken panels here and there, but mostly they survived...
(they did better than the cars did- smashed windscreens and 'panelbeaten' bodywork everywhere- the local car dealership lost every car on the lot- all brand new and not a straight panel left on any of them....)

 

[Crazy Dave]

Removed

 

[ian33a]

Here's a little something I knocked up to reduce my energy bill and with the pending price increases next month should pay for itself quite quickly.

View attachment 132061

The house roof faces in the wrong direction so these face south.

I bet your neighbours love you

 

[Crazy Dave]

I bet your neighbours love you

Neighbours don't have any problems at all, in fact they are considering doing the same and were asking me how much it all costs.
Edit: Anyway it's not just about me it's about all of us doing what we can to improve our environmental impact.

 

[Dabop]

Here's a little something I knocked up to reduce my energy bill and with the pending price increases next month should pay for itself quite quickly.

View attachment 132061

The house roof faces in the wrong direction so these face south.

Just realised that I was in PM when I was talking about this lol, but direction is of far less importance than many think...
Your roof looks like it would be ideal for an 'east/west' split...

Another factor is direction is actually far less important than many believe....
My previous house (because of building constraints) had 3kw of PV facing east, and 3kw of PV facing west (the very small north facing roof was almost entirely taken up by solar HWS thermal panels)
We actually had an identical system (6kw all facing north) installed by the same company two days after ours, by the same crew even lol-was installed at the neighbours place

That literally zeroed our electric bill (of course feedin tariffs, usage etc all makes a difference)
View attachment 131987
left pic is east PV array and the thermal HWS panels with the west bank out of sight on the far side (you can see why I said they 'had to be' east/west lol) and an overhead from google earth...

We for the first few months used to have 'solar races' with the neighbours lol, comparing our two systems- and it was interesting to see the difference- ours started pretty much as soon as half the sun was above the horizon on the east bank- his was over an hour later before it even started, and ours was well over a kw by that stage... our east bank peaked about 10, and then started dropping- but by then the west bank had fired up as well.. and it worked right up until sunset- again long after the neighbours had shut down...
So we had a longer but lower peak, his was shorter but higher...
Funnily enough- on sunny days- they were pretty much identical sometimes ours was a hundred whs ahead, sometimes his...
Where we found a HUGE difference was overcast- where ours dropped of course- but his dropped far more- leaving us well in the lead- often by 5kwh a day or more!!!

That was unexpected...

(I put it down to on full overcast days, the light becomes a 'diffuse source' rather than a point source like on sunny days- and because his north facing panels could only 'see' half the sky, where ours facing east and west could 'see' the entire sky- our performance in overcast was better...)

In summer we were getting about 32kwh a day from 6kw of panels and we often 'got money back' on the electric bills- not much $20-$40- but using electricity AND getting a 'negative bill'- that was nice...
View attachment 131988
(that was a winter bill hence the lower daily output)

View attachment 131989
That was the very first day of full production about two weeks before Christmas in 2016... (31.8kwh)

That was from a PM conversation

 

[Crazy Dave]

Just realised that I was in PM when I was talking about this lol, but direction is of far less importance than many think...
Your roof looks like it would be ideal for an 'east/west' split...

That was from a PM conversation

Thank for sharing, unfortunately I couldn't view the images as I don't have permission. LOL

 

[Dabop]

Thank for sharing, unfortunately I couldn't view the images as I don't have permission. LOL

lol- showed up for me...
first one was

 

[Blister]

I keep considering solar with battery, this discussion is useful and its good to hear from people who actually have systems installed.
I just keep thinking that it's a shame to put holes in my perfectly good roof. Knowing my luck I would need to fix my roof one year after installing the panels !
For this reason I like the idea of the actual tiles/slates being solar so you could replace the roof in one go and get less issues with wind loading etc, it looks better etc. The price is mad for these at the moment.
I wouldn’t mind if the entire roof was made of big panels actually but not sure this is available. Seems silly to have a roof on the roof.

Ollie

When my 10 panels were fitted the installer pushed one tile up over the one above it , after the bracket was fixed to the roof timber the tile was slid back down , NO holes

 

[Stevekane]

This clearly needs checking out but a chap I know said his elderly mother is getting her totally free solar panels fitted today, its a scheme for anyone with an income of less than £30.000, and its not one where the company keeps the FIT or anything,,,I must look into it.
Steve.

 

[Phil Pascoe]

I had the same offer from the county council - it depends upon the EPC of your property. If yours qualifies you should probably have had it. (Mine has been insulated etc. since the EPC was done - it was a joke, anyway).

 

[Richard_C]

You've probably heard today that VAT on energy saving products - including solar panels - will be removed so an installation will (should) be 20% less from 1 April. That and rising electricity prices might change the equation.

I have thought carefully about pv panels on and off for some years but still not done it. I will think again now. A few things bother me - life of panels and the decline in efficiency over time being one, but the main worry was and perhaps still is the dodgy-ness of the industry. It seems a bit wild west, first there was rent a roof with no proper explanation of any risks on house sale, then there are guarantees and if they will be honoured, companies come and go *, cost and margin - all companies need to make a profit but I remember when FIT was cut suddenly the installation cost fell massively which suggests that margins were very high, cold calling from 'energy consultants' ** and so on. Unregulated or lightly regulated businesses shouldn't really be trusted with something of major long term importance. Who can you trust? I'm sure there are some good installers out there and many happy customers but I'll bet that there are a good many unhappy ones as well.

* A company set up with great fanfare on the edge of our village, rented barns/workshop/showroom etc from local farmer and offered everything 'green' from wood pellet boilers to pv installations. Someone I know had work done by them but they wouldn't come to sort out a problem. I had a dig around - they had disappeared. Companies house search, wound up but because it was a voluntary wind up no directors were disquaified. Search the directors on companies house and they had started and wound up companies before.

** A good reply to a cold call from an energy consultant is "so what are your qualifications?" Stops them in their tracks - "you say you are energy consultants so I presume you must be qualified in some way otherwise anyone could set up and start phoning people " ... I just make the appointments .. "fine, but will the person you send be qualified..."