Discussion
PCoulson said:
No being a powerfully built company director (overweight local government officer) I don't have the funds for a proper system but what are peoples thoughts on https://www.pluginsolar.co.uk/?product_cat=plug-in...
Reading up it seems there much contradictory info on how diy-able they are. I'd be capable of doing the work but I don't want something that causes problems such as invalidating my house insurance.
I can't answer for the insurance but I built my system and it was dead easy. It would be even easier today as I built my battery banks from individual cells and now you can get plug and play server rack batteries cheaply.Reading up it seems there much contradictory info on how diy-able they are. I'd be capable of doing the work but I don't want something that causes problems such as invalidating my house insurance.
https://signaturesolar.com/eg4-lifepower4-lithium-...
AW10 said:
What is your current annual electricity use?
How much are they predicting you can use directly from the panels?
How much are they predicting you will divert to the battery and then use later?
I suspect your payback estimate is unrealistically optimistic.
Currently we use around 6000 kWh annually How much are they predicting you can use directly from the panels?
How much are they predicting you will divert to the battery and then use later?
I suspect your payback estimate is unrealistically optimistic.
They’re predicting 5500 kWh production annually and 70-85% bring used onsite depending in the battery size (5.2 or 10.4kwh). The location is pretty much perfect, south facing with no shade from sunrise to sunset as we live on top of a hill.
They haven’t specified the amount stored but the fact that the use depends on the battery size implies that for at least some of the time the smaller battery would be fully charged I think. Payback was 9 years at an elec rate of 28p. Shorter at current rates but they are unlikely to last that long I guess.
Adding a solar iBoost or plugging an EV in during the summer days might increase the use % a bit I expect.
Does all that sound reasonable? They seem to have used all the appropriate industry standard assumptions from what I can see.
For the financial payback side I would suggest planning on the panels reducing your import by about 1/3 and a battery by about the same again. If you achieve better than that in real world use then that’s icing on the cake.
Using up to 85% in house is quite unlikely to happen without an EV.
A while back I posted a friend’s data: 3.55 kWp system and a 5.2 kWh battery installed about 18 months ago. South facing roof in Fareham with no shading. “Normal” domestic use - 2 people in a 3 bed semi with gas CH. Over the course of a year he and his wife used 2561 kWh of electricity. 769 kWh was consumed straight off the panels. 978 kWh (an average of less than 3 kWh per day) came from the battery. The remaining 814 kWh came from the grid. So he has saved about 1750 kWh per year. At 36p per kWh that’s £630/year.
The issue with a battery is that when you have loads of excessive generation to charge it (the summer) is when the days are longest and brightest and you’re least likely to need it. In the winter you’ll have many days where you have virtually no excess capacity so the battery will be all but empty at the end of a short day.
Using up to 85% in house is quite unlikely to happen without an EV.
A while back I posted a friend’s data: 3.55 kWp system and a 5.2 kWh battery installed about 18 months ago. South facing roof in Fareham with no shading. “Normal” domestic use - 2 people in a 3 bed semi with gas CH. Over the course of a year he and his wife used 2561 kWh of electricity. 769 kWh was consumed straight off the panels. 978 kWh (an average of less than 3 kWh per day) came from the battery. The remaining 814 kWh came from the grid. So he has saved about 1750 kWh per year. At 36p per kWh that’s £630/year.
The issue with a battery is that when you have loads of excessive generation to charge it (the summer) is when the days are longest and brightest and you’re least likely to need it. In the winter you’ll have many days where you have virtually no excess capacity so the battery will be all but empty at the end of a short day.
Thanks, that’s very helpful.
In my mind the cost of the panels and their efficiency is largely out of your hands. The decision is whether to prioritise reducing your carbon footprint by having as large a system as possible and exporting excess in the summer, or cost effectiveness by choosing a system that allows you to use all the energy generated in the summer accepting that you will need to import more in the winter.
Your 1/3, 2/3 rule sounds a good target, as does using an EV to balance the load.
Thank you for the info
In my mind the cost of the panels and their efficiency is largely out of your hands. The decision is whether to prioritise reducing your carbon footprint by having as large a system as possible and exporting excess in the summer, or cost effectiveness by choosing a system that allows you to use all the energy generated in the summer accepting that you will need to import more in the winter.
Your 1/3, 2/3 rule sounds a good target, as does using an EV to balance the load.
Thank you for the info
Arnold Cunningham said:
I'm still procastinating about that 2nd battery, having now worked out that when I spend a day in the garage, we go from 10 to over 16 kWh. Or I can spend the money on a roamerdrive for the landy.
Anyway - on immersion heaters - I was also wondering if a normal wifi switch such as this could be used : https://www.screwfix.com/p/tcp-1-gang-1-way-smart-...
It's a 3kW heater and the switch is rated to 13A.
The proper iBoost type system is cleverer. If you just have the immersion switched on a timer, it will come on full pelt (generally 3kW) whether your panels are producing that or not, so a good chance that you end up importing from the grid or discharging from the battery if you have one. Anyway - on immersion heaters - I was also wondering if a normal wifi switch such as this could be used : https://www.screwfix.com/p/tcp-1-gang-1-way-smart-...
It's a 3kW heater and the switch is rated to 13A.
Edited by Arnold Cunningham on Monday 26th September 15:20
Edited by Arnold Cunningham on Monday 26th September 16:02
The "proper" setup actually throttles the immersion to only allow it to draw the excess being produced by the panels.
If you have a battery and am EV being charged, it is unlikely you will get to the point where you actually turn on the immersion. Depends on the size of your panels.
Does the iBoost come with a new immersion heater or does it use the existing one?
I’m not familiar with how hot water is usually heated in the uk. Is it generally gas, with an immersion heater that can be manually activated as backup?
How is the life expectancy of this immersion heater impacted if you start using it as your main heating for 4-5-6 months of the year? Are they cheap to replace?
I’m not familiar with how hot water is usually heated in the uk. Is it generally gas, with an immersion heater that can be manually activated as backup?
How is the life expectancy of this immersion heater impacted if you start using it as your main heating for 4-5-6 months of the year? Are they cheap to replace?
V-spec said:
Does the iBoost come with a new immersion heater or does it use the existing one?
It uses the existing immersion. The iBoost is simply wired between your immersion switch and the immersion, with a sender in your electricity meter monitoring for import/export with a clamp the cable coming into your house.
I think Aw10's point is why I want the biggest battery I can afford. I want to minimise consumption from the grid during peak times AND consume a good chunk from the panels. I feel it should be quite doable to consume hardly anything from the grid during the summer months and hardly anything during peak times in the winter months.
Do I think peak vs off-peak will stick around? In some fashion, for sure. Maybe not the same as today - but certainly somehow.
Do I think peak vs off-peak will stick around? In some fashion, for sure. Maybe not the same as today - but certainly somehow.
Arnold Cunningham said:
I think Aw10's point is why I want the biggest battery I can afford. I want to minimise consumption from the grid during peak times AND consume a good chunk from the panels. I feel it should be quite doable to consume hardly anything from the grid during the summer months and hardly anything during peak times in the winter months.
Do I think peak vs off-peak will stick around? In some fashion, for sure. Maybe not the same as today - but certainly somehow.
I think you’ll struggle in the winter. A page or two back I posted generation figures by month gathered over 10 years. If you look at those figures versus what you consume in those months I don’t think you’ll generate enough surplus to do any meaningful battery charging to get you though the night, so to speak.Do I think peak vs off-peak will stick around? In some fashion, for sure. Maybe not the same as today - but certainly somehow.
I’ll be frank - solar panels (and battery storage) for me are purely a financial transaction. If the payback period is too long I’m simply not interested. Being green and reducing carbon foot print and dependency on the grid/Putin is all good and fine but do remember this is Pistonheads.
AW10 said:
I think you’ll struggle in the winter. A page or two back I posted generation figures by month gathered over 10 years. If you look at those figures versus what you consume in those months I don’t think you’ll generate enough surplus to do any meaningful battery charging to get you though the night, so to speak.
I’ll be frank - solar panels (and battery storage) for me are purely a financial transaction. If the payback period is too long I’m simply not interested. Being green and reducing carbon foot print and dependency on the grid/Putin is all good and fine but do remember this is Pistonheads.
HaHaI’ll be frank - solar panels (and battery storage) for me are purely a financial transaction. If the payback period is too long I’m simply not interested. Being green and reducing carbon foot print and dependency on the grid/Putin is all good and fine but do remember this is Pistonheads.
Mind you I need to offset todays trackday which was 11mpg (actually better than I thought) although the drive down was 25mpg.
I’m following this with interest as I would like to reduce reliance on the grid generally. As long as it’s a reasonable payback man maths can be used to justify expenditure. I don’t see it much maybe because of combi boilers but whatever happened to those water heating tubes you would see on rooftops?
Arnold Cunningham said:
I think Aw10's point is why I want the biggest battery I can afford. I want to minimise consumption from the grid during peak times AND consume a good chunk from the panels. I feel it should be quite doable to consume hardly anything from the grid during the summer months and hardly anything during peak times in the winter months.
Do I think peak vs off-peak will stick around? In some fashion, for sure. Maybe not the same as today - but certainly somehow.
The thing with batteries is that you can add more as you can afford them.Do I think peak vs off-peak will stick around? In some fashion, for sure. Maybe not the same as today - but certainly somehow.
I'm one of what I suspect is the majority of people in the UK who didn't really understand their usage and the details and nuances of it. Yes, turn lights off, don't use the immersion heater, boil only the water you actually need in the kettle and the bill goes down, but never really paid attention to TV's on standby, computer on all the time etc.
Since opting for solar panels and (necessary for the export) getting a smart meter and understanding usage better, I have found it quite interesting.
Our panels and battery have been in for 2 months now. Here are the results:
646 * 0.3 = £193.8 generated (and used by us) in that 2 months.
215 * 0.3 = £ 65 used from the grid.
Per month at the moment = £97 saved versus £32 spent
Exported 120kWh @ 5p/kWh = £6 ! Pah!
August was a good month as would be expected, September has been hit and miss, only generating 5kWh on some days. Battery has not been full since August apart from all last week when we were away on holiday and had turned pretty much everything off. So a bigger battery will not have helped. Still on the fence about overnight charging due to the higher "day rate" and difficulty of getting onto those tariffs. Want to see what winter usage looks like as well before committing to anything.
So as the rate is going up to 35p, we are looking at a saving of £114/month. Best case! £1370/year - means 10.9 years, let's say 11 year payback period. Yes, during the winter it will be less - but we do still tend to get quite a few sunny clear days down here even during the winter - and this is assuming that the per unit price does not go up. Best case therefore at the moment is a 11 year payback. I am OK with that. Also doing our bit to help the environment and reduce the load on the national grid feels good. At the time we had them installed, there was talk of unit prices going up to >60p kWh, which in all honesty factored into our decision to jump in. Now the price has been capped it worsens the payback period but it is still viable.
Also interesting to consider the contribution from the panels and battery vs their installation cost.
Of the 646kWh generated, 205kWh have come from the panels directly, and 437kWh have gone into the battery and then back out again in the evenings (which would otherwise have been lost/exported).
So that is 32% directly from the panels (which were 60% of the installation cost) and 68% via the battery (which was 40% of the installation cost).
So in theory the battery is saving us £76.5 of the £114, therefore the battery will have paid for itself in 6.6 years, less if we do eventually go onto overnight charging. On that basis, the panels themselves are only saving us £37.5/month (£450/year) - meaning a payback period for the panels of 20 years!
CAVEAT: OK, all these figures will likely be worse over the winter and I am probably being overly optimistic.
Our panels stop any meaningful generation by late afternoon/early evening, but annoyingly the face of the roof that doesn't have any panels is often in brilliant sunshine for a couple more hours after this - we thought about getting a few more panels up there (can only realistically fit 3 - not much space because it is a fairly small roof section with a dormer). This would help with a bit more contribution to the battery charge levels, but would also delay the time at which we start using the battery so it lasts better through the night, but were quoted an additional £2,300 from the company that did our installation - which includes an aluminium skirt around the panels to prevent birds from accessing underneath, but does not include scaffolding (dormer bungalow so may or may not need it)..... That seems expensive to me given that the panels seem to be about £150 each... Potentially those three panels might add an average of 4kWh/day (all useable) so saving £511/year meaning 4.5 years payback.... hmmmm - not sure what to do on that one. It seems expensive, but on the face of it a short(ish) payback period.
Since opting for solar panels and (necessary for the export) getting a smart meter and understanding usage better, I have found it quite interesting.
Our panels and battery have been in for 2 months now. Here are the results:
646 * 0.3 = £193.8 generated (and used by us) in that 2 months.
215 * 0.3 = £ 65 used from the grid.
Per month at the moment = £97 saved versus £32 spent
Exported 120kWh @ 5p/kWh = £6 ! Pah!
August was a good month as would be expected, September has been hit and miss, only generating 5kWh on some days. Battery has not been full since August apart from all last week when we were away on holiday and had turned pretty much everything off. So a bigger battery will not have helped. Still on the fence about overnight charging due to the higher "day rate" and difficulty of getting onto those tariffs. Want to see what winter usage looks like as well before committing to anything.
So as the rate is going up to 35p, we are looking at a saving of £114/month. Best case! £1370/year - means 10.9 years, let's say 11 year payback period. Yes, during the winter it will be less - but we do still tend to get quite a few sunny clear days down here even during the winter - and this is assuming that the per unit price does not go up. Best case therefore at the moment is a 11 year payback. I am OK with that. Also doing our bit to help the environment and reduce the load on the national grid feels good. At the time we had them installed, there was talk of unit prices going up to >60p kWh, which in all honesty factored into our decision to jump in. Now the price has been capped it worsens the payback period but it is still viable.
Also interesting to consider the contribution from the panels and battery vs their installation cost.
Of the 646kWh generated, 205kWh have come from the panels directly, and 437kWh have gone into the battery and then back out again in the evenings (which would otherwise have been lost/exported).
So that is 32% directly from the panels (which were 60% of the installation cost) and 68% via the battery (which was 40% of the installation cost).
So in theory the battery is saving us £76.5 of the £114, therefore the battery will have paid for itself in 6.6 years, less if we do eventually go onto overnight charging. On that basis, the panels themselves are only saving us £37.5/month (£450/year) - meaning a payback period for the panels of 20 years!
CAVEAT: OK, all these figures will likely be worse over the winter and I am probably being overly optimistic.
Our panels stop any meaningful generation by late afternoon/early evening, but annoyingly the face of the roof that doesn't have any panels is often in brilliant sunshine for a couple more hours after this - we thought about getting a few more panels up there (can only realistically fit 3 - not much space because it is a fairly small roof section with a dormer). This would help with a bit more contribution to the battery charge levels, but would also delay the time at which we start using the battery so it lasts better through the night, but were quoted an additional £2,300 from the company that did our installation - which includes an aluminium skirt around the panels to prevent birds from accessing underneath, but does not include scaffolding (dormer bungalow so may or may not need it)..... That seems expensive to me given that the panels seem to be about £150 each... Potentially those three panels might add an average of 4kWh/day (all useable) so saving £511/year meaning 4.5 years payback.... hmmmm - not sure what to do on that one. It seems expensive, but on the face of it a short(ish) payback period.
TriumphStag3.0V8 said:
I'm one of what I suspect is the majority of people in the UK who didn't really understand their usage and the details and nuances of it. Yes, turn lights off, don't use the immersion heater, boil only the water you actually need in the kettle and the bill goes down, but never really paid attention to TV's on standby, computer on all the time etc.
Since opting for solar panels and (necessary for the export) getting a smart meter and understanding usage better, I have found it quite interesting.
Our panels and battery have been in for 2 months now. Here are the results:
646 * 0.3 = £193.8 generated (and used by us) in that 2 months.
215 * 0.3 = £ 65 used from the grid.
Per month at the moment = £97 saved versus £32 spent
Exported 120kWh @ 5p/kWh = £6 ! Pah!
August was a good month as would be expected, September has been hit and miss, only generating 5kWh on some days. Battery has not been full since August apart from all last week when we were away on holiday and had turned pretty much everything off. So a bigger battery will not have helped. Still on the fence about overnight charging due to the higher "day rate" and difficulty of getting onto those tariffs. Want to see what winter usage looks like as well before committing to anything.
So as the rate is going up to 35p, we are looking at a saving of £114/month. Best case! £1370/year - means 10.9 years, let's say 11 year payback period. Yes, during the winter it will be less - but we do still tend to get quite a few sunny clear days down here even during the winter - and this is assuming that the per unit price does not go up. Best case therefore at the moment is a 11 year payback. I am OK with that. Also doing our bit to help the environment and reduce the load on the national grid feels good. At the time we had them installed, there was talk of unit prices going up to >60p kWh, which in all honesty factored into our decision to jump in. Now the price has been capped it worsens the payback period but it is still viable.
Also interesting to consider the contribution from the panels and battery vs their installation cost.
Of the 646kWh generated, 205kWh have come from the panels directly, and 437kWh have gone into the battery and then back out again in the evenings (which would otherwise have been lost/exported).
So that is 32% directly from the panels (which were 60% of the installation cost) and 68% via the battery (which was 40% of the installation cost).
So in theory the battery is saving us £76.5 of the £114, therefore the battery will have paid for itself in 6.6 years, less if we do eventually go onto overnight charging. On that basis, the panels themselves are only saving us £37.5/month (£450/year) - meaning a payback period for the panels of 20 years!
CAVEAT: OK, all these figures will likely be worse over the winter and I am probably being overly optimistic.
Our panels stop any meaningful generation by late afternoon/early evening, but annoyingly the face of the roof that doesn't have any panels is often in brilliant sunshine for a couple more hours after this - we thought about getting a few more panels up there (can only realistically fit 3 - not much space because it is a fairly small roof section with a dormer). This would help with a bit more contribution to the battery charge levels, but would also delay the time at which we start using the battery so it lasts better through the night, but were quoted an additional £2,300 from the company that did our installation - which includes an aluminium skirt around the panels to prevent birds from accessing underneath, but does not include scaffolding (dormer bungalow so may or may not need it)..... That seems expensive to me given that the panels seem to be about £150 each... Potentially those three panels might add an average of 4kWh/day (all useable) so saving £511/year meaning 4.5 years payback.... hmmmm - not sure what to do on that one. It seems expensive, but on the face of it a short(ish) payback period.
This mirrors my thoughts almost 100%Since opting for solar panels and (necessary for the export) getting a smart meter and understanding usage better, I have found it quite interesting.
Our panels and battery have been in for 2 months now. Here are the results:
646 * 0.3 = £193.8 generated (and used by us) in that 2 months.
215 * 0.3 = £ 65 used from the grid.
Per month at the moment = £97 saved versus £32 spent
Exported 120kWh @ 5p/kWh = £6 ! Pah!
August was a good month as would be expected, September has been hit and miss, only generating 5kWh on some days. Battery has not been full since August apart from all last week when we were away on holiday and had turned pretty much everything off. So a bigger battery will not have helped. Still on the fence about overnight charging due to the higher "day rate" and difficulty of getting onto those tariffs. Want to see what winter usage looks like as well before committing to anything.
So as the rate is going up to 35p, we are looking at a saving of £114/month. Best case! £1370/year - means 10.9 years, let's say 11 year payback period. Yes, during the winter it will be less - but we do still tend to get quite a few sunny clear days down here even during the winter - and this is assuming that the per unit price does not go up. Best case therefore at the moment is a 11 year payback. I am OK with that. Also doing our bit to help the environment and reduce the load on the national grid feels good. At the time we had them installed, there was talk of unit prices going up to >60p kWh, which in all honesty factored into our decision to jump in. Now the price has been capped it worsens the payback period but it is still viable.
Also interesting to consider the contribution from the panels and battery vs their installation cost.
Of the 646kWh generated, 205kWh have come from the panels directly, and 437kWh have gone into the battery and then back out again in the evenings (which would otherwise have been lost/exported).
So that is 32% directly from the panels (which were 60% of the installation cost) and 68% via the battery (which was 40% of the installation cost).
So in theory the battery is saving us £76.5 of the £114, therefore the battery will have paid for itself in 6.6 years, less if we do eventually go onto overnight charging. On that basis, the panels themselves are only saving us £37.5/month (£450/year) - meaning a payback period for the panels of 20 years!
CAVEAT: OK, all these figures will likely be worse over the winter and I am probably being overly optimistic.
Our panels stop any meaningful generation by late afternoon/early evening, but annoyingly the face of the roof that doesn't have any panels is often in brilliant sunshine for a couple more hours after this - we thought about getting a few more panels up there (can only realistically fit 3 - not much space because it is a fairly small roof section with a dormer). This would help with a bit more contribution to the battery charge levels, but would also delay the time at which we start using the battery so it lasts better through the night, but were quoted an additional £2,300 from the company that did our installation - which includes an aluminium skirt around the panels to prevent birds from accessing underneath, but does not include scaffolding (dormer bungalow so may or may not need it)..... That seems expensive to me given that the panels seem to be about £150 each... Potentially those three panels might add an average of 4kWh/day (all useable) so saving £511/year meaning 4.5 years payback.... hmmmm - not sure what to do on that one. It seems expensive, but on the face of it a short(ish) payback period.
Likewise I'm fine with a breakeven in around 10 years or so as the bonus is doing something positive to reduce our environmental impact (and yes I realise that the most important thing is ti reduce consumption, we're trying hard to do this wherever it is practical.)
Likewise we have realised that we could add a few more panels on the garage roof to catch some afternoon sun, which if wired into the main inverter don't cost that much and should mean the battery is used more efficiently.
What size battery compared with your panels did you go for?
Thanks, very interesting.
markiii said:
i keep hearing people say they want to reduce their eco impact, has anyone analysed the eco cost of making the panels and batteries to determine if that's actually true, my money is on not
It's unsurprisingly pretty complex to model, but you are right, it needs to be considered.There are two issue, the carbon footprint of solar panels (otherwise sometimes called the life-cycle greenhouse gas emissions) and the other forms of pollution created by an energy source.
The Life cycle greenhouse gas emissions of solar have been estimated at around 3.5–12 gCO2eq/kWh, while for fossil fuels they are around 475 gCO2eq/kWh (both these figures take into account the mining or drilling of fossil fuels, transport and then burning them, while for solar it is only the CO2 released by obtaining the raw materials, manufacturing the panels and transporting them as once installed they don't produce any further carbon.)
So Solar panels are massive more environmentally friendly in carbon terms
They do have a problem with non carbon pollution (both during manufacture and once recycling) though and this is definitely something to consider. Of course fossil fuels also produce other forms of pollution and environmental damage quite apart from CO2, and the different types of fuel vary in their impact, as do other non fossil sources such as nuclear, wind etc.
But in pure CO2 terms, solar panels do seem to make very good sense, from what I've read. Unless we are gong to massively invest in nuclear power stations (which I actually think is the right thing to do) and quickly then the CO2 issue does seem to be the most pressing one at the moment. At an individual level it is the only practical thing one can do apart from obviously reducing your consumption of energy.
https://www.nature.com/articles/s41560-017-0032-9
https://www.ecowatch.com/solar-environmental-impac...
https://www.iea.org/reports/global-energy-co2-stat...
Tobermory said:
This mirrors my thoughts almost 100%
Likewise I'm fine with a breakeven in around 10 years or so as the bonus is doing something positive to reduce our environmental impact (and yes I realise that the most important thing is ti reduce consumption, we're trying hard to do this wherever it is practical.)
Likewise we have realised that we could add a few more panels on the garage roof to catch some afternoon sun, which if wired into the main inverter don't cost that much and should mean the battery is used more efficiently.
What size battery compared with your panels did you go for?
Thanks, very interesting.
It's 4.8kW of panels (but peaks at about 4kW as the panels are in 2 banks facing different directions). Battery is 9.6kWh.Likewise I'm fine with a breakeven in around 10 years or so as the bonus is doing something positive to reduce our environmental impact (and yes I realise that the most important thing is ti reduce consumption, we're trying hard to do this wherever it is practical.)
Likewise we have realised that we could add a few more panels on the garage roof to catch some afternoon sun, which if wired into the main inverter don't cost that much and should mean the battery is used more efficiently.
What size battery compared with your panels did you go for?
Thanks, very interesting.
One other thing on the environmental side is that it does encourage the mindset of minimising grid use and paying much more attention to consumption, which is a good thing.
Edited by TriumphStag3.0V8 on Friday 30th September 20:19
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