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Energy prices - gone nuts.

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I think your spreadsheet is really good, but agree knowing when to stop is hard - it's so much guesswork that in reality, by changing a couple of assumptions, you could make it either show that it's a no-brainer to invest, or the exact opposite. I find it very hard to know what is remotely realistic in terms of assumptions tbh.

Here's an example of opportunity cost over 10 years with fairly pessimistic (some economists would say realistic) future interest rates, taking into account compounding of interest. Column C is what would need subtracting from the values in your 'Saving' column to give a fair reflection of what was really saved per annum (assuming you agreed with my interest rate guesses).

View attachment 177255
I just stuck in 8% on a simple interest basis! It still seems to be a goer.
 
I know I’m getting boring now but I’ll try stop myself very soon 😂
It’s 6:40 and I’m currently updating 3 pinballs with the new insider code, Gabes playing FIFA on his PS5 and I’m cooking his T and I’m still chucking electric away this late in the day.

012C6FB3-C799-4C81-AD27-7429C7F0EE6C.jpegE60BEA44-2FAF-41DA-978E-E0846B5BBDA8.png
 
Looks like i probably need a new gas boiler (before they’re banned) and maybe these new fangled gel filled wet system radiators. probably looking at a spend of £15k to get a 30% reduction in my gas usage. another spreadsheet in the offing
 
I just stuck in 8% on a simple interest basis! It still seems to be a goer.
Alan if you insert a new row at row 9 and then put the cost 10,995 as a negative in cell d9 so that column D reads -10,995, 1,233, 1,289, etc and then use the formula =irr(0.05,d9:d34) in, say, cell k2 that will give you the compound interest rate you would need to earn each year over the 25 years in order to match the solar panel investment.
 
Alan if you insert a new row at row 9 and then put the cost 10,995 as a negative in cell d9 so that column D reads -10,995, 1,233, 1,289, etc and then use the formula =irr(0.05,d9:d34) in, say, cell k2 that will give you the compound interest rate you would need to earn each year over the 25 years in order to match the solar panel investment.
You will need to format cell k2 as a %. Eg 0.05 = 5%
 
Wow, not many places you can get a net of tax return like that.
But you need to take account of new batteries every 10 years also, which brings it down to 15.8%

IRR
17.7%​
IRR
15.8%​
-10500​
-10500​
28.345,1581,4621,462
29.765,1321,5271,527
31.245,1061,5951,595
32.815,0811,6671,667
34.455,0551,7411,741
36.175,0301,8191,819
37.985,0051,9011,901
39.884,9801,9861,986
41.874,9552,0752,075
43.964,9302,167- 4,488- 2,321
46.164,9052,2642,264
48.474,8812,3662,366
50.894,8572,4722,472
53.444,8322,5822,582
56.114,8082,6982,698
58.924,7842,8192,819
61.864,7602,9452,945
64.964,7363,0773,077
68.204,7133,2143,214
71.614,6893,358- 7,311- 3,953
75.194,6663,5083,508
78.954,6423,6653,665
82.904,6193,8293,829
87.054,5964,0014,001
91.404,5734,1804,180
 
Other factors to consider above and beyond the spreadsheet numbers;

reduced dependency on the grid
lower carbon footprint
increased resilience to grid outages
Iv been told these systems are not resilient to grid outages unless you have a special version which can isolate itself completely. Reason being when the power goes and the workers are repairing the line they don’t want houses feeding power back into it electrocuting them. I think the system will just shut down lol on a power cut?

I looked at mine today in the meter box and can’t see anyway it could isolate it self from the grid so think it would just shut down.
 
Alan if you insert a new row at row 9 and then put the cost 10,995 as a negative in cell d9 so that column D reads -10,995, 1,233, 1,289, etc and then use the formula =irr(0.05,d9:d34) in, say, cell k2 that will give you the compound interest rate you would need to earn each year over the 25 years in order to match the solar panel investment.
At a general level, I'd question if it makes sense doing any of these calcs over 25 years :hmm:

More than half of us on here will likely be dead before 25 years, and even more of us will have moved house within that period. I'd have thought 10 years was an absolute max for most people when doing the maths (Alan's circumstances might be different, I'm just trying to generalise), with a majority of people moving house more frequently than that and therefore never seeing a financial return.

Also war with Ukraine will be long over, new power generation facilities will be online, new power generation technologies will be available, etc, etc. It just seems way too far out into the future to predict prices / inflation with the remotest degree of accuracy.
 
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If I’m still here in 10yr 8 be more happy about still being able to play pinball and the money I’ve spent would be the last thing on my mind.
When buying mine money wasn’t a consideration when getting my setup it was more to be worry free on future bills when the wife retires.
Now selling a house surely that would add some value to it in this day and age.
 
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the problem with spreadsheets is the humans who create them. you end up manipulating the outcome to what you want it to be.

dug out my old smart meter monitor which amazingly still works even though i’ve changed suppliers twice since getting it. it’s even showing the correct tariff prices which i thought it wouldn’t be able to get!

mrs has gone out so i’m measuring my background usage. no lights on. just the fridges, freezers, chargers computers wifi etc. it’s around 500w.

**** myself when i switched the kettle on as that jumps it up to 3.2kw 😂
 
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The Tesla Powerwall can be told to cut itself off the grid. It all goes via the backup gateway, designed for grid outages which is the reason the systems is a lot more expensive. If the grid went out, I can isolate and manage this via bluetooth directly to the gateway. The gateway is a full consumer unit where you can set it up for things to be run on backup, vs things to be dropped. The battery has a reserve level you can adjust and it will stop discharge when reached. If only your essential stuff was wired up for backup, then this will happen automatically. For now, I will run around and turn off none essential stuff and should have half a day of backup. Or it can protect power outages that were not expected to happen.
These features will not give you a ROI unless you can put a value on have consistent power.

Worth repeating, some inverters are powered by AC and can not be run via the DC solar panels or a DC battery store. It is always worth asking if the system will work when the grid isn't supplying power.

If you have a battery with a warranty for 10 years, they are likely expecting the system will still work in 10 year. I have no expectation the battery will have the same charge depth as it has when new, year on year it will degrade. In 10 years it might be 60%, if any of you are still alive I will let you know. ;)

There is an obsession with how much money these systems will save you, pay themselves off in x years. I have got caught up in it too as I try to justify to folks why the investment was worth it because the question is so common. There are many good reasons to install systems that generate energy from free natural resources, if they also are cost neutral over a period of time, then understand it but if the aim is to invest purely to make money then there will always be better options.
 
I'm on the side of a mountain and get a fair amount of Wind... Anyone installed a Wind turbine?? :)

To be fair, i get the sun a lot of the time too (South facing).. the initial outlay just scares me for varying returns.
 
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Iv been told these systems are not resilient to grid outages unless you have a special version which can isolate itself completely. Reason being when the power goes and the workers are repairing the line they don’t want houses feeding power back into it electrocuting them. I think the system will just shut down lol on a power cut?

I looked at mine today in the meter box and can’t see anyway it could isolate it self from the grid so think it would just shut down.

You are right about the cutting off of power when the grid is down, I think its referred to as Islanding, so if the grid goes off you loose the output from the solar inverter.

On my battery inverter there is an EPS (Emergency Power Supply) option so if the grid goes down you cant run some crucial devices like a fridge, broadband router, etc. But to wire this up its a separate connection on the inverter and you need to use a switching relay for the required circuit as that is designed to prevent the back feeding mentioned into the grid.
 
There is an obsession with how much money these systems will save you, pay themselves off in x years. I have got caught up in it too as I try to justify to folks why the investment was worth it because the question is so common. There are many good reasons to install systems that generate energy from free natural resources, if they also are cost neutral over a period of time, then understand it but if the aim is to invest purely to make money then there will always be better options.
I think a lot of the posts in this thread give the impression that people are 'saving' money - hence perhaps the misconception/obsession. And a lot (most?!) of the current interest in them is purely financial, and whether they offer a better value alternative to paying electricity providers.

Aligned with your comment above though, and based on the calcs Alan did (which seem to be based on reasonable assumptions), it seems clear that they don't really 'save' money, and breaking even in 10 years is quite possibly/likely the best case.

It would be good if the government added this tech to the grants being offered for new boilers/heat source pumps, etc, as the financial case for them would be a lot more appealing with a £5k discount - and the volume of sales that generated would help bring costs down in the longer term due to economies of scale.
 
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I have ZERO faith in this government or what ever criminals come in next in fixing the energy crises issue, So don't expect any fix any time soon, and by the time it does come the panels will probably have mostly paid for them self and I wont give a **** either. It's all a gamble, will be interesting to see what the future brings :)
 
tesla powerwall. am i right in assuming that can only be charged via ac mains voltage?
The main one in the UK is charging via AC but there is an all in one with a DC solar inverter. Mine was aware of when there was excess solar power going for export and would use it to charge the battery. The gateway can do it pretty accurately because it measures voltage and amps, rather than a CT clamp, it responded very quickly. It could also be set to charge from the grid at an off peak point too.
 
I have ZERO faith in this government or what ever criminals come in next in fixing the energy crises issue, So don't expect any fix any time soon, and by the time it does come the panels will probably have mostly paid for them self and I wont give a **** either. It's all a gamble, will be interesting to see what the future brings :)
The same criminals come everytime they're voted in. There is no energy crisis it's all man made to squeeze you for the 2030 You will own nothing and be happy crap.


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The last 12 years has seen such an inconsistent and switching approach to grants for this type of technology that I believe the aim is to look like such things are available but they are much harder to get. Companies who ramped up to provide in the market, then left as they were not always getting paid or the schemes were changing. When we did our roof, we were eligible for a grant for the insulation, to bring it up to modern standards but we couldn't find anyone who wanted the work because it would need to be a tailored job.

Rising energy costs means that Truss is offering to scrap the green tax, meaning there will be less grants available.
The actual cost of energy would come down if more of us were generating and exporting it because the utility companies wouldn't then need to buy so much. But storage systems are needed to really fix it as peak time is often when folks are not generating as much. Except for @Colywobbles who seems to have a monster system.
 
The last 12 years has seen such an inconsistent and switching approach to grants for this type of technology that I believe the aim is to look like such things are available but they are much harder to get. Companies who ramped up to provide in the market, then left as they were not always getting paid or the schemes were changing. When we did our roof, we were eligible for a grant for the insulation, to bring it up to modern standards but we couldn't find anyone who wanted the work because it would need to be a tailored job.

Rising energy costs means that Truss is offering to scrap the green tax, meaning there will be less grants available.
The actual cost of energy would come down if more of us were generating and exporting it because the utility companies wouldn't then need to buy so much. But storage systems are needed to really fix it as peak time is often when folks are not generating as much. Except for @Colywobbles who seems to have a monster system.
Mostly the problem of me not being able to use it and it’s getting shoved to the grid. However on your recommendation I have set the wheels on motion to hopefully get a hot water tank fitted and fed via the solar panels so we have free water on tap.
This will save further meaning the Combi won’t have to kick in which is the main use of our Gas.
 
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