Solar PV - economics?
Discussion
DonkeyApple said:
Road2Ruin said:
4.5% though, that's still less than inflation.
But that's not pertinent when comparing two yields or their capital risk etc. You could contrast each against inflation but if the yields are comparable you have the same end result.
Where you could try to include inflation would be with the capital growth of the equity portfolio which stands a fair chance of matching or exceeding versus the sunk cost of equipment which is a near 100% write off.
Road2Ruin said:
DonkeyApple said:
Road2Ruin said:
4.5% though, that's still less than inflation.
But that's not pertinent when comparing two yields or their capital risk etc. You could contrast each against inflation but if the yields are comparable you have the same end result.
Where you could try to include inflation would be with the capital growth of the equity portfolio which stands a fair chance of matching or exceeding versus the sunk cost of equipment which is a near 100% write off.
dmsims said:
Wyy do you need that much battery ?
I’ve got a high usage and high phantom load so have 26kW of Solar PV (or will do when the last panels are fitted in a couple of weeks). So it seemed to make sense to have a fairly large battery. So many variables though, so more than willing to admit it may be overkill. Even since placing the order I’ve changed to Octopus Agile which has cut my bill by 35-40% alone. I don’t think those prices will endure year round though. But it has made my break even point a fair bit longer.Dave726 said:
I just had 2 (so 27kW usable capacity) plus the gateway installed for £18.5k (at the same time as the PV install).
With all the variables like potentially adding new EV’s into the mix I’m not sure it will ever be possible to know exactly how successful my choices have been or when the exact break even point will be.
Dave726 said:
I’ve got a high usage and high phantom load so have 26kW of Solar PV (or will do when the last panels are fitted in a couple of weeks). So it seemed to make sense to have a fairly large battery. So many variables though, so more than willing to admit it may be overkill. Even since placing the order I’ve changed to Octopus Agile which has cut my bill by 35-40% alone. I don’t think those prices will endure year round though. But it has made my break even point a fair bit longer.
With all the variables like potentially adding new EV’s into the mix I’m not sure it will ever be possible to know exactly how successful my choices have been or when the exact break even point will be.
Can always take up arc welding garden ornaments for Etsy. With all the variables like potentially adding new EV’s into the mix I’m not sure it will ever be possible to know exactly how successful my choices have been or when the exact break even point will be.
U.K. Gas went below £55 this week so it's back down to its long term average so it'll be interesting to see how long utilities are allowed to keep prices up for. If the price of U.K. gas and TTF stay down here for a while the media will start picking up on it.
DonkeyApple said:
Can you show your payback calculation and account for opportunity cost? That would be really beneficial as I've not yet been able to achieve a positive outcome and the numbers have become worse recently due to the elevated costs while on the other side the risk free rate is now hitting nearly 5%.
It would also really help to see the carbon calculations/estimates for the whole of life and compare against the local Grid supply.
I could do the former but frankly not the latter….carbon calcs are beyond the average householder, which I perhaps am It would also really help to see the carbon calculations/estimates for the whole of life and compare against the local Grid supply.
That article already suggested the total life is 25 years, which I personally feel is utter b
ks, but if you want to agreed with it that is fine.Our solar is done and dusted: installed Nov 2010, cost 13k, that was recovered within 7 years and the FIT means we have around 2.5k coming in annually….so pretty easy to be happy.
Equivalent system today would be a LOT less cost, although we did get the encouraging FIT to help ROI.
I wasn’t a stockbroker and don’t compare every investment with what I could get from the markets…..which of course have proven they can go down as well as up
The battery? We got a LuxPower inverter and 14.4kWh of Pylontech batteries, installed for under £6.5k. Might cost a bit more now….prices went a little crazy last year.
My amateur sums suggest our flat repayment should be within 4-6 years, but of course there is wasted opportunity cost - I could have punted that 6.5k on the next Apple and been thousands down!
Or….I could figure that within 10 years we will safely be ‘in profit’, and that my personal opinion* is that it feels the right thing to do, because we can.
It feels like you’ve been agonising over this for a long time, mostly berating the decisions made by feckless people deploying solar &/or battery, and that perhaps you would be better just….er…..not worrying about it: nobody is forcing you to install anything!!
* others will disagree, & that’s fine: we are all just humans. Maybe get your Chatbot to discuss it with my Bard
OldSkoolRS said:
Just because it works for us as low users doesn't mean it will work for everyone else though, especially given our unique trade price installation. There is also a question regarding potential tax for any excess generation/export 'profit' too, which doesn't seem to be followed up on at the moment, but the rules are already in place:
https://www.gov.uk/hmrc-internal-manuals/business-...
If you're generating more that 20% over what your house needs, then in theory you should be paying tax on the export credit...not sure anyone does yet, but could screw things up for our plan as we export 2 times what we use in these good months. I need to export enough to cover all our annual electricity use, standing charge for electricity and gas, plus ideally some gas use too in order to hit an ROI of 6 years if I include lost interest on the money I could have put into a 5 year bond (5.20% at the moment).
It's all about intention, so as long as you don't massively overspec the array, I don't think there will ever be a problem. And if there was a question of taxing the income, then you would need to take into account the costs of generating that income... https://www.gov.uk/hmrc-internal-manuals/business-...
If you're generating more that 20% over what your house needs, then in theory you should be paying tax on the export credit...not sure anyone does yet, but could screw things up for our plan as we export 2 times what we use in these good months. I need to export enough to cover all our annual electricity use, standing charge for electricity and gas, plus ideally some gas use too in order to hit an ROI of 6 years if I include lost interest on the money I could have put into a 5 year bond (5.20% at the moment).
Edited by OldSkoolRS on Sunday 4th June 15:31
MaxFromage said:
It's all about intention, so as long as you don't massively overspec the array, I don't think there will ever be a problem. And if there was a question of taxing the income, then you would need to take into account the costs of generating that income...
I hope not. I confess I was completely unaware of the information in my link until after we'd had ours installed. The extra number of panels (and therefore the bigger inverter) was more to allow us to generate enough to cover our use each end of winter and just leave us with 3-4 months of not generating enough to cover use. It looks like every good summer month will also export enough for two winter months, so we could be 'over' by four months by end of August. That's assuming we'd generate nothing until the next April, but obviously that won't be the case, so that will add to the 'profit' as well. Good for getting a shorter ROI, but reading that link was a surprise to me if they did start coming back to us for it.Is this what you mean by phantom load?
"A phantom load is the amount of power drawn by an electronic device when it's not in use, but is still plugged in. Contrast this to the operating load, which is the amount of power a device consumes when it's actually in use"
Surely you want to audit your enegy usage?
I replaced pond pumps, an amplifier and put some things on Wifi plugs
"A phantom load is the amount of power drawn by an electronic device when it's not in use, but is still plugged in. Contrast this to the operating load, which is the amount of power a device consumes when it's actually in use"
Surely you want to audit your enegy usage?
I replaced pond pumps, an amplifier and put some things on Wifi plugs
Dave726 said:
I’ve got a high usage and high phantom load so have 26kW of Solar PV (or will do when the last panels are fitted in a couple of weeks). So it seemed to make sense to have a fairly large battery. So many variables though, so more than willing to admit it may be overkill. Even since placing the order I’ve changed to Octopus Agile which has cut my bill by 35-40% alone. I don’t think those prices will endure year round though. But it has made my break even point a fair bit longer.
With all the variables like potentially adding new EV’s into the mix I’m not sure it will ever be possible to know exactly how successful my choices have been or when the exact break even point will be.
With all the variables like potentially adding new EV’s into the mix I’m not sure it will ever be possible to know exactly how successful my choices have been or when the exact break even point will be.
mikeiow said:
DonkeyApple said:
Can you show your payback calculation and account for opportunity cost? That would be really beneficial as I've not yet been able to achieve a positive outcome and the numbers have become worse recently due to the elevated costs while on the other side the risk free rate is now hitting nearly 5%.
It would also really help to see the carbon calculations/estimates for the whole of life and compare against the local Grid supply.
I could do the former but frankly not the latter….carbon calcs are beyond the average householder, which I perhaps am It would also really help to see the carbon calculations/estimates for the whole of life and compare against the local Grid supply.
That article already suggested the total life is 25 years, which I personally feel is utter b
ks, but if you want to agreed with it that is fine.Our solar is done and dusted: installed Nov 2010, cost 13k, that was recovered within 7 years and the FIT means we have around 2.5k coming in annually….so pretty easy to be happy.
Equivalent system today would be a LOT less cost, although we did get the encouraging FIT to help ROI.
I wasn’t a stockbroker and don’t compare every investment with what I could get from the markets…..which of course have proven they can go down as well as up
The battery? We got a LuxPower inverter and 14.4kWh of Pylontech batteries, installed for under £6.5k. Might cost a bit more now….prices went a little crazy last year.
My amateur sums suggest our flat repayment should be within 4-6 years, but of course there is wasted opportunity cost - I could have punted that 6.5k on the next Apple and been thousands down!
Or….I could figure that within 10 years we will safely be ‘in profit’, and that my personal opinion* is that it feels the right thing to do, because we can.
It feels like you’ve been agonising over this for a long time, mostly berating the decisions made by feckless people deploying solar &/or battery, and that perhaps you would be better just….er…..not worrying about it: nobody is forcing you to install anything!!
* others will disagree, & that’s fine: we are all just humans. Maybe get your Chatbot to discuss it with my Bard
I've not yet found someone who has that data which strikes me as unusual when people are stating the investment side.
Re the stockbroking stuff, it's not about being a stock broker it's simply about how any investment is not made in isolation so is always contrasted to other simple opportunities. Not single stock gambling but just the very basic figures for risk free and capital at risk etc.
It's not that I am agonising over my own decisions at all. I've looked at my numbers and acted now for over ten years accordingly. For me I just look at things periodically but I am still not seeing how the home generation and home storage is the better option yet. And because I do not have a closed mind I find myself asking those who state that they have to help me see the numbers if only to check my workings. However, I've not yet seen a case where the numbers are better and quite a few people become very defensive which is an a tribute that I see a lot among gamblers in a hole which raises my suspicions further.
Okay…..I’m months behind updating this - for years I recorded the week end solar readings (manually!). This year we went skiing for a month then just back from Interrailing for 2 months 
Also about to submit a FIT reading (I think it now pays around 43p/kWkh), & you can see our new inverter made a difference….still feel our original (a pair - two strings) were under-specc’d. Used ThinkGreenPartners to replace - a pushy business, but we wanted it sorting, so all good!
Oh, & I didn’t drop the £1k cost of that replacement in here, so numbers in reality are a tad worse (but the generation is much better, so offset in perhaps 4 years). Take that out of the ‘profits number
So by my calcs, the raw cost payback was 8.6 years to payback…but once savings are *estimated*, that dropped to 7.2yrs.
Pretty happy with that ‘investment’….but of course we could likely have made more on the markets. Or less, depending what we did….
FIT is no longer (think you have SEG or something?) but our panels would likely cost less than half what we paid (& be a bit more efficient now). Solar+batteries=zero VAT too.
Any more helpful?
YMMV
Also about to submit a FIT reading (I think it now pays around 43p/kWkh), & you can see our new inverter made a difference….still feel our original (a pair - two strings) were under-specc’d. Used ThinkGreenPartners to replace - a pushy business, but we wanted it sorting, so all good!
Oh, & I didn’t drop the £1k cost of that replacement in here, so numbers in reality are a tad worse (but the generation is much better, so offset in perhaps 4 years). Take that out of the ‘profits number
So by my calcs, the raw cost payback was 8.6 years to payback…but once savings are *estimated*, that dropped to 7.2yrs.
Pretty happy with that ‘investment’….but of course we could likely have made more on the markets. Or less, depending what we did….
FIT is no longer (think you have SEG or something?) but our panels would likely cost less than half what we paid (& be a bit more efficient now). Solar+batteries=zero VAT too.
Any more helpful?
YMMV
mikeiow said:
Okay…..I’m months behind updating this - for years I recorded the week end solar readings (manually!). This year we went skiing for a month then just back from Interrailing for 2 months
Also about to submit a FIT reading (I think it now pays around 43p/kWkh), & you can see our new inverter made a difference….still feel our original (a pair - two strings) were under-specc’d. Used ThinkGreenPartners to replace - a pushy business, but we wanted it sorting, so all good!
Oh, & I didn’t drop the £1k cost of that replacement in here, so numbers in reality are a tad worse (but the generation is much better, so offset in perhaps 4 years). Take that out of the ‘profits number
So by my calcs, the raw cost payback was 8.6 years to payback…but once savings are *estimated*, that dropped to 7.2yrs.
Pretty happy with that ‘investment’….but of course we could likely have made more on the markets. Or less, depending what we did….
FIT is no longer (think you have SEG or something?) but our panels would likely cost less than half what we paid (& be a bit more efficient now). Solar+batteries=zero VAT too.
Any more helpful?
YMMV
Yes. Thanks. Calcs today obviously don't include FIT as you point out. How much can you sell at 43p as the obvious arbitrage is to sell all the solar and then load the battery overnight with cheap Grid. Even only being able to sell the excess at a near market rate skews the numbers hugely in favour. Also about to submit a FIT reading (I think it now pays around 43p/kWkh), & you can see our new inverter made a difference….still feel our original (a pair - two strings) were under-specc’d. Used ThinkGreenPartners to replace - a pushy business, but we wanted it sorting, so all good!
Oh, & I didn’t drop the £1k cost of that replacement in here, so numbers in reality are a tad worse (but the generation is much better, so offset in perhaps 4 years). Take that out of the ‘profits number
So by my calcs, the raw cost payback was 8.6 years to payback…but once savings are *estimated*, that dropped to 7.2yrs.
Pretty happy with that ‘investment’….but of course we could likely have made more on the markets. Or less, depending what we did….
FIT is no longer (think you have SEG or something?) but our panels would likely cost less than half what we paid (& be a bit more efficient now). Solar+batteries=zero VAT too.
Any more helpful?
YMMV
Can you calculate the payback duration without FIT?
In my situation I'm still hearing via gas so the electricity usage is too low for any self generation or storage set up to be remotely viable against just putting the money in the markets. The clear pivot point takes place when the gas boiler can't be replaced and the house has to go pure electric and that is some years away. That will also coincide with EV cars being in the garage.
Edited by DonkeyApple on Monday 5th June 08:57
As has been stated, everyone's case will be different to everyone else's. One factor which does not appear in recent discussions here is the introduction of an EV into the mix.
I have an EV with 200+ mile range, which at this time of year I charge almost exclusively from excess solar. I do not yet have an export MPAN so cannot get paid for exporting energy to the grid, so no lost income is caused by filling the car. Only on (rare) 200-mile journeys do I ever use a public charger, while I also occasionally have to charge the car from the grid at home (due to poor planning on my part). My overall cost per mile since buying the car 21 months ago is 3.3p/mile, compared with 15-25p/mile for my previous daily drivers. The cost of buying the car was marginally more than a similar ICE car, while servicing costs are a lot lower. Factoring that into the payback period of my PV panels makes a huge difference to my payback period.
I have an EV with 200+ mile range, which at this time of year I charge almost exclusively from excess solar. I do not yet have an export MPAN so cannot get paid for exporting energy to the grid, so no lost income is caused by filling the car. Only on (rare) 200-mile journeys do I ever use a public charger, while I also occasionally have to charge the car from the grid at home (due to poor planning on my part). My overall cost per mile since buying the car 21 months ago is 3.3p/mile, compared with 15-25p/mile for my previous daily drivers. The cost of buying the car was marginally more than a similar ICE car, while servicing costs are a lot lower. Factoring that into the payback period of my PV panels makes a huge difference to my payback period.
Not quite the definition I meant. I meant more what the house power consumption is in the background, regardless of whether anyone is at home and also overnight. It's things that can't be switched off like the crestron system (and other stuff in the AV rack), burglar alarm panels (due to the house being extended considerably 10 years ago some stuff like that is very inefficient).
I had actually gone against the advice of the AV installer and switched the power off to the rack overnight but this cuts power to the CCTV and some other stuff that it's nice to have running so it's not ideal. now that I'm charging the powerwalls fully every day I leave it on. Will have to see what the powerwall status is during the winter months before deciding what to do going forward.
I had actually gone against the advice of the AV installer and switched the power off to the rack overnight but this cuts power to the CCTV and some other stuff that it's nice to have running so it's not ideal. now that I'm charging the powerwalls fully every day I leave it on. Will have to see what the powerwall status is during the winter months before deciding what to do going forward.
dmsims said:
Is this what you mean by phantom load?
"A phantom load is the amount of power drawn by an electronic device when it's not in use, but is still plugged in. Contrast this to the operating load, which is the amount of power a device consumes when it's actually in use"
Surely you want to audit your enegy usage?
I replaced pond pumps, an amplifier and put some things on Wifi plugs
"A phantom load is the amount of power drawn by an electronic device when it's not in use, but is still plugged in. Contrast this to the operating load, which is the amount of power a device consumes when it's actually in use"
Surely you want to audit your enegy usage?
I replaced pond pumps, an amplifier and put some things on Wifi plugs
Dave726 said:
I’ve got a high usage and high phantom load so have 26kW of Solar PV (or will do when the last panels are fitted in a couple of weeks). So it seemed to make sense to have a fairly large battery. So many variables though, so more than willing to admit it may be overkill. Even since placing the order I’ve changed to Octopus Agile which has cut my bill by 35-40% alone. I don’t think those prices will endure year round though. But it has made my break even point a fair bit longer.
With all the variables like potentially adding new EV’s into the mix I’m not sure it will ever be possible to know exactly how successful my choices have been or when the exact break even point will be.
With all the variables like potentially adding new EV’s into the mix I’m not sure it will ever be possible to know exactly how successful my choices have been or when the exact break even point will be.
Dave726 said:
base load stuff...
I've got 2 PWs. Fwiw my base load is around 1kwh (cctv, comms, usual household appliances) with total daily use around 25kwh if I exclude EVs. In winter we generally only use off peak as I fully charge the PWs overnight and get a handful of kw off the panels during the daylight hours. Even on days when there is no solar power generated we rarely tip into peak rate usage.Penny Whistle said:
As has been stated, everyone's case will be different to everyone else's. One factor which does not appear in recent discussions here is the introduction of an EV into the mix.
I have an EV with 200+ mile range, which at this time of year I charge almost exclusively from excess solar. I do not yet have an export MPAN so cannot get paid for exporting energy to the grid, so no lost income is caused by filling the car. Only on (rare) 200-mile journeys do I ever use a public charger, while I also occasionally have to charge the car from the grid at home (due to poor planning on my part). My overall cost per mile since buying the car 21 months ago is 3.3p/mile, compared with 15-25p/mile for my previous daily drivers. The cost of buying the car was marginally more than a similar ICE car, while servicing costs are a lot lower. Factoring that into the payback period of my PV panels makes a huge difference to my payback period.
Yes it can work both ways. In your case it results in a higher return/quicker repayment of the costs. However for some, the EV may well be costing them more overall than a previous ICE and so they are not actually saving, but actually reducing the motoring cost closer to what it was previously.I have an EV with 200+ mile range, which at this time of year I charge almost exclusively from excess solar. I do not yet have an export MPAN so cannot get paid for exporting energy to the grid, so no lost income is caused by filling the car. Only on (rare) 200-mile journeys do I ever use a public charger, while I also occasionally have to charge the car from the grid at home (due to poor planning on my part). My overall cost per mile since buying the car 21 months ago is 3.3p/mile, compared with 15-25p/mile for my previous daily drivers. The cost of buying the car was marginally more than a similar ICE car, while servicing costs are a lot lower. Factoring that into the payback period of my PV panels makes a huge difference to my payback period.
As long as you have a photo of your meter showing the current export numbers, you will get paid from this point even though registration may take many months.
From May to September, most of my EV charging is effectively at the SEG rate. As the SEG rate increases, so does the cost of motoring!
Further to the Smart Export Guarantee (SEG) info, I applied in August 2022 and am still waiting. The bonus is that Scottish Power's SEG was 5.5p when I applied and was the best we could do as a business. They are now competing with Octopus and this has increased to 12p... Payback is reduced from 5 years down to 4.5.
Hmm we are similar and have a pond as well - base load is 550W - think you need to look into what's actually chewing that up
M1AGM said:
Dave726 said:
base load stuff...
I've got 2 PWs. Fwiw my base load is around 1kwh (cctv, comms, usual household appliances) with total daily use around 25kwh if I exclude EVs. In winter we generally only use off peak as I fully charge the PWs overnight and get a handful of kw off the panels during the daylight hours. Even on days when there is no solar power generated we rarely tip into peak rate usage.dmsims said:
Hmm we are similar and have a pond as well - base load is 550W - think you need to look into what's actually chewing that up
All my comms and cctv is around 700 watts at night according to my poe switches, then we have a few bits around the property that have a small use on standby so 1kw is about right.M1AGM said:
Dave726 said:
base load stuff...
I've got 2 PWs. Fwiw my base load is around 1kwh (cctv, comms, usual household appliances) with total daily use around 25kwh if I exclude EVs. In winter we generally only use off peak as I fully charge the PWs overnight and get a handful of kw off the panels during the daylight hours. Even on days when there is no solar power generated we rarely tip into peak rate usage.Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff