Are domestic solar panels financially beneficial - or just ideological?

[Mothergoose]

Yes, Clubman, it's true. When I was living in the UK and only home every 2nd weekend, my daughter was living there and following my pattern of usage as I has explained why to her. In the summertime, we were getting 35kwh per day, 10 panels, south facing, south east of the country. The panels on the south facing roof were only installed in July 24. The panels in the house where my son lives are east/west facing, installed, Jan 25, and were producing just about half of what the south facing panels were producing in the summer. Today the south facing panels produced 20kwh. Our consumption today - it's a little chilly - so electric stove on all day was 10.4kwh.

Re the tax on it - my understanding is that I need to pay tax on anything over 400 that I earn from the grid. However, it is also.my understanding that there woukd be no tax liability if my daughter's name was on the bill, as we would both be able to rmearn 400 from the grid. However, this wasn't a possibility this year as my daughter couldn't decide whether she was staying at home or moving away.

Re standing charges - yes, of course, I still have to pay these but at least the electricity is without cost now.

Re the PSO, I don't know whether I need to pay this levy from my profits also - I will ask my accountant about this.

 

[hazelgreen]

One point I would mention is that it is not feasible to add on extra panels to the system. Our house has roof with 4 aspects and the south facing one only takes four panels. But we maxed out by putting more on the east and west ones to get full potential to provide for a large house. The house is too big for us now but a decent solar system would be good feature if selling.

 

[Luternau]

Is this considered income and assessable for income tax etc.?

Yea. Any export income above €400 is taxable. It's €400 per person named on the bill, not per supply address.

 

[ArthurMcB]

You woukd need to be exporting over approx 4000 kwh's per annum to go over the 800 mark (if two named on bill). Thats a lot of export but defo is dooable if you have an array size of 7kwp + and a sunny summer and no ev, for example.

 

[I'm Nobody]

Latest update,
our last electric bill is €370 to the plus side, compared to 2023.
Also in 2024 I ordered a thousand litres of Kerosene in January and in June.
This year I ordered a thousand litres in January and a thousand litres today.
So I am hoping that in 2026 that I might get away with just one order for the year.
All depending on how the weather is for the next few months of course.

 

[Colin4444]

thats misleading quoting like that since it makes it look like an investment with dividends and capital appreciation, with a typical investment the 8,000 euro initial capital can always be sold back to the market reclaiming your capital and usually asset appreciation. With solar panels you cannot get back your investment so you really need to be adding depreciation cost aswell for 10 years, 10% per year probably . Then after 10 years if the panels are still working you can use 17.5% return but probably the system won't be so effective after 10 years in operation.

Yep this is the part all solar enthusiasts fail to mention, or dont understand themselves..

 

[Colin4444]

The warranty documentation for my Trina solar panels states that their performance will decline by a maximum of 2 % after one year
and that the maximum degradation from year 2 to 25 will be 0.55% annually, meaning that after 10 years the panels will be about 93% as efficient as they are today. And the battery performance will decline; it is guaranteed to hold at least 60% of the full charge after a decade.

The expected lifetime of my inverter ranges between 10 - 15 years, so it will be approaching replacement time in a decade.

On the positive side, in ten years time, the price of replacement inverters and batteries is likely to have fallen significantly.

And what manufacturers quote is always very optimistic and not real life, take EV range quoted by manufacturers and then what people realistically get from them..

Seems very arbitrary that it would decline by max 2% in first year and then .55% after that, why 2% in first year? the decline between year 2 and year 9 the same? It all seems a little untrue

 

[Colin4444]

The proof of the pudding is in the eating, and myself and anyone i know who gotten solar is getting a very good return on their investment.

The only people questioning the return on a solar panel investment are people who haven't gotten them and likely never will because it'd be in conflict with their world view. People who can do maths either have them already or are planning to.

It sometimes feels that people with solar are very defensive, and the investment they made. Ppl dont generally criticise solar they just ask questions about it as they dont have the system so therefore dont understand it.. best to go in with eyes open to fully understand the system - set expectations etc. This is just doing due diligence before investing, which is what everyone says you should do..

One thing Im reading ATM in the Irish Solars Owners Group on FB is how the batteries dont work properly in the cold, they are not charging fully at night and dont discharge correctly either, see below. Good to know these things, as one might then place the battery in an insulated area etc..

 

[Colin4444]

In time the feedback tariff will be greatly reduced and possibly abolished entirely.

Longer term the ideal approach will be to have as many panels as possible and a decent sized battery and configure your life around using all your own generated energy... directly fom the panels and off your battery storage.

I wonder also about the ev / night time rate, as alot of people use the battery to charge on this rate to use during the day..
Both of these - feedback tariff and ev / night rate - make up a portion of the savings ppl mention with solar and their ROI / payback of system.
For some this portion can be very high, making the payback on their system alot longer than they initially thought!

 

[conor_mc]

Both of these - feedback tariff and ev / night rate - make up a portion of the savings ppl mention with solar and their ROI / payback of system.
For some this portion can be very high, making the payback on their system alot longer than they initially thought!

Can only speak for myself, but I would have lowballed generation etc in my considerations so it more or less evens out. Plus, and possibly the major factor, I did not assume any energy price inflation to reach my 7 year payback calculation. So all in all, I think I'm still tracking ahead of my expected payback despite any battery/charging/FiT drawbacks.

 

[conor_mc]

Seems very arbitrary that it would decline by max 2% in first year and then .55% after that, why 2% in first year? the decline between year 2 and year 9 the same? It all seems a little untrue

It's absolutely not untrue, and there are plenty of academic papers about Light Induced Degradation / Potential Induced Degradation as well as manufacturer testing to substantiate it. As you can imagine, the .55% is a ceiling that the manufacturers guarantees, rather than a target they expect to hit!

 

[Colin4444]

It's absolutely not untrue, and there are plenty of academic papers about Light Induced Degradation / Potential Induced Degradation as well as manufacturer testing to substantiate it. As you can imagine, the .55% is a ceiling that the manufacturers guarantees, rather than a target they expect to hit!

I'll stand corrected, but you cant blame me for doubting manufacturer claims... you have to agree what they claim for EV range is exaggerated, they are choosing the most optimistic, efficient figures, which is not the way ppl drive...

 

[Leo]

And what manufacturers quote is always very optimistic and not real life, take EV range quoted by manufacturers and then what people realistically get from them..

It's not that both these cases are optimistic, it's that manufacturers must use standardised testing methodologies to make it easier for regular consumers to understand. Each individual's circumstances will rarely match the lab conditions required for that testing, so experiences vary, but the regs mean that you and I can easily compare the performance of competing products and not have to dig into the fine print about how each manufacturer arrived at their capacity or range figures.

Seems very arbitrary that it would decline by max 2% in first year and then .55% after that, why 2% in first year? the decline between year 2 and year 9 the same? It all seems a little untrue

Shouldn't really be a surprise as material degradation is rarely linear.

 

[Colin4444]

Shouldn't really be a surprise as material degradation is rarely linear.

But it is linear after year 1

 

[Colin4444]

It's not that both these cases are optimistic, it's that manufacturers must use standardised testing methodologies to make it easier for regular consumers to understand. Each individual's circumstances will rarely match the lab conditions required for that testing, so experiences vary, but the regs mean that you and I can easily compare the performance of competing products and not have to dig into the fine print about how each manufacturer arrived at their capacity or range figures.

Fair point, its just annoying that these standards never compare with real life..

 

[Leo]

Fair point, its just annoying that these standards never compare with real life..

That's the nature of picking a very specific set of repeatable test criteria. They only coincide with reality occasionally. It's certainly better than each manufacturer getting to choose the optimal values for a number of criteria that maximises their own figures. It would be very difficult for a typical user to compare one manufacturer's efficiency against another if we had to get the calculators out to examine temperature coefficients, ambient temperature, assumed solar energy per sqm, etc..

 

[Colin4444]

That's the nature of picking a very specific set of repeatable test criteria. They only coincide with reality occasionally. It's certainly better than each manufacturer getting to choose the optimal values for a number of criteria that maximises their own figures. It would be very difficult for a typical user to compare one manufacturer's efficiency against another if we had to get the calculators out to examine temperature coefficients, ambient temperature, assumed solar energy per sqm, etc..

Probably best to ignore manufacturers claims and rely more on third-party testing and customer reviews..

 

[Leo]

Probably best to ignore manufacturers claims

Well, the idea of the standardised testing is that it should be a reliable guide to relative performance. Two panels with the same rating under those test conditions will have very similar performance in your own situation. There will likely be small variations, one may perform better at lower temperatures for example, or slightly better at a different angle, but the variance should be small enough to make little difference.

 

[qwerty5]

One thing Im reading ATM in the Irish Solars Owners Group on FB is how the batteries dont work properly in the cold, they are not charging fully at night and dont discharge correctly either, see below. Good to know these things, as one might then place the battery in an insulated area etc..

Some batteries come with a heater. I got mine set up last year (A sigenergy system in November). During the coldest nights the charging took longer but was still inside the 3 hour window I have for our EV rate. The batteries heat up if they're below 0 degrees. There's some cost to that obviously but the power it used for these seemed neglible.

 

[Marsupial]

Seems very arbitrary that it would decline by max 2% in first year and then .55% after that, why 2% in first year? the decline between year 2 and year 9 the same? It all seems a little untrue And what manufacturers quote is always very optimistic and not real life, take EV range quoted by manufacturers and then what people realistically get from them..

Ah, but the colourful graph on the leaflet is very attractive - and I'm a sucker for a colourful graph!

Incidentally, given that there aren't any moving parts or batteries in/on my solar panels, your EV analogy isn't really valid.