Scrutable

lpm wrote: Wed Apr 19, 2023 9:39 pm Haven't had time to run the numbers.

But it's more like buying an annuity than making an investment. A 40 year annuity is very expensive. An inflation-linked annuity that can be inherited by a spouse even more expensive. An annuity that's index linked to wholesale electricity prices doesn't exist, but is quite attractive.

Looks like we pay £3,000 to buy a 40-year annuity with £170 income p.a.. 5.6%. I think that's OK. A normal inflation-linked annuity would cost that, I believe.

lpm wrote: Wed Apr 19, 2023 10:29 pm
There are now several more electricity supply companies onboard, it's no longer just Octopus.

lpm wrote: Wed Apr 19, 2023 9:39 pm Haven't had time to run the numbers.

But it's more like buying an annuity than making an investment. A 40 year annuity is very expensive. An inflation-linked annuity that can be inherited by a spouse even more expensive. An annuity that's index linked to wholesale electricity prices doesn't exist, but is quite attractive.

Looks like we pay £3,000 to buy a 40-year annuity with £170 income p.a.. 5.6%. I think that's OK. A normal inflation-linked annuity would cost that, I believe.

IvanV wrote: Thu Apr 20, 2023 9:52 am My solar panels are going on my roof today. They will be assisted by 7 kWh of batteries. 6 of the 10 panels will have solar panel optimisers, which I had not heard of until a few days ago.

I have been told, and it seems to be true, that if one panel in a connected array is shaded, reducing its output in comparison to those that are unshaded in that array, then the output from all the panels in that array is reduced to the level of the worst. This because they are wired in series, and a panel with low output presents a higher resistance that reduces the current from the entire sequence. I confess I don't quite follow that argument, but I haven't found anyone saying that's rubbish. This is the problem that the optimisers overcome. There are other solutions, but they are more expensive.

Unfortunately optimisers aren't exactly cheap, at least not yet, and you need one per panel within an array suffering substantial variations in shading. Modelling provided by the supplier suggested I would lose about a third of my output without them, and that was only taking account of shading from the roof, and not from the trees that will also have some impact on those six panels on the western side of my house. That adds about £500 to the installation.

Locating the inverter and batteries has been difficult in a house with no loft. The inverter and batteries have to be adjacent. I thought they could go in an under-eave cupboard in a bedroom, but that won't provide the clearances the inverter needs. So they are going somewhere that my wife will be somewhat annoyed by, in the study, as that provides a suitably uninterrupted piece of external wall, where the new boiler also had to go.

It's quite a complicated installation, with 4 panels in 2 separate areas on my eastern facing roof, and the other 6 on my flat roof, above a single storey exension, facing south. I also have a south facing garage roof, but it would be very costly to run cables under the block paved drive.

So coming out a fair bit more expensive than my father's installation, but my roof is much more complicated than most. All the council's fault for refusing my first proposed roof conversion, which would have had a huge uninterrupted south-facing roof slope, and removed the rear flat roof. Council insisted instead on this E-W roof arrangement with interruptions from large dormer windows, and retaining the flat roof.

Another complication I will have to face is when the flat roof needs refelting in about 5 years. I have had to ensure that the panels on the roof can be easily lifted. They are not physically stuck down, rather they are weighted down by a couple of heavy blocks under the panel to stop them blowing away. So it should be possible to lift them when the roof needs refelting.

Woodchopper wrote: Thu Apr 20, 2023 9:02 am

lpm wrote: Wed Apr 19, 2023 9:39 pm Haven't had time to run the numbers.

But it's more like buying an annuity than making an investment. A 40 year annuity is very expensive. An inflation-linked annuity that can be inherited by a spouse even more expensive. An annuity that's index linked to wholesale electricity prices doesn't exist, but is quite attractive.

Looks like we pay £3,000 to buy a 40-year annuity with £170 income p.a.. 5.6%. I think that's OK. A normal inflation-linked annuity would cost that, I believe.

Forty years seems too long. As far as I remember, people I know who've installed them reckon on an operating lifetime of about 25-30 years before the panels need to be replaced. They may be being cautious though.

Also, its only inflation linked in terms of the electricity price. Possible (and predicted by you earlier) that the electricity price will decrease relative to other prices - ie general inflation could be much higher than electricity price inflation. That's fine if your only concern is to ensure that the electricity bill is covered but there could be an opportunity cost compared to an investment that is linked to general inflation.

Imrael wrote: Tue Jun 27, 2023 10:22 am My storage battery works in power cuts and I wasnt aware of doing any extra paperwork. It is a Tesla Powerwall so somewhat fancy - I guess the standard installation includes that aspect.

We do get a brief "dip" when mains power comes back on - sometimes enough to restart PC's and unset clocks.

IvanV wrote: Tue Jun 27, 2023 10:19 am Solar panels, it turns out, nor storage batteries, don't usually work in power cuts. At least not in a standard installation,

A rather disappointing discovery from the other day, when we had a couple of power cuts adding up to several hours. It had never occurred to me this might be the case, so I had not done any research in advance.

It seems that it is a legal requirement that your equipment cut out in a power cut, to protect electricity workers, who would otherwise find the demand side cable was live when working in a power cut.

You can set your house up to avoid this, if you make specific arrangements. First, you need an isolating switch so you can isolate your house from the mains during a power cut. This can be an automatic relay, or a manual switch. But it is still complicated getting your equipment to work safely once you are islanded from grid, which otherwise acts as a stabilising mechanism to avoid overloads from your solar panels. So it might be best to disconnect the solar panels, and just run from your batteries. Though your batteries will have limited power, and it may be limited what you can power during a power cut. Then there is the management issue that if you want to have your batteries as a reserve, it might be a good idea to make sure that there is some energy available when you need it. Normally you'd just drain them to make maximum use of your solar energy. So if you kept a reserve, then you would be making less efficient use of your solar panels.

Which all begs the question, is it worth trying?

According to Ofgem's 2021-22 electricity distribution performance report in my distribution area, SSEN, I should have a power cut about once every 2 years, and have an average of 50 mins downtime per year. But the frequency I have to reset things due to power cuts, it is evident that here they come more often, and with a longer average downtime. Maybe the fact that we are right on the edge of the distribution company's area means that we have less resilience in our supply. The recent supply cut was due to a falling tree taking out a power line. The second cut was deliberate, to take out the temporary line they initially put in to get the power up and running, and reconnect the overhead supply. We have buried cables along our road, but they are fed from overhead cables between the towns, and not every street in the area has buried cables. My previous house in the same mini-conurbation had overhead supply.

jaap wrote: Tue Jun 27, 2023 12:19 pm About 10 days ago there was a housefire in Arnhem in the Netherlands. It started in the kitchen of a terraced house, one in a block of 8 houses.
The firefighters found it impossible to stop the fire from spreading to the other houses in the block, because the roof was completely covered in solar panels. In the end 4 of the houses completely burned down, and the other 4 will probably have to be demolished.

The panels protected the fire from the water, and allowed the fire to travel unimpeded in the gap behind the panels to the other houses. Rooftiles can easily be removed, even by the water jet itself, but solar panels cannot. They cannot be removed until the power has been cut, and even then remain dangerous due to the voltage they continue to generate. So it takes time to tackle the problem, during which the fire can keep spreading. Burning solar panels are also hazardous, as they can send shards everywhere.

There are some calls for legislation to make sure various safety guidelines are enforced, such as leaving a half metre gap between the panels of one house and the next.

Link to Dutch article

Grumble wrote: Tue Jun 27, 2023 12:09 pm If you have an unreliable supply, what’s it worth to you to make it more reliable? That’s the question really. In terms of making best use of solar power that’s not really a factor as such, you’re getting greener power when power is available.

Grumble wrote: Tue Jun 27, 2023 12:09 pm If you have an unreliable supply, what’s it worth to you to make it more reliable? That’s the question really. In terms of making best use of solar power that’s not really a factor as such, you’re getting greener power when power is available.

Martin Y wrote: Tue Jun 27, 2023 4:12 pm It makes sense that you'd need to isolate your house from the incoming mains supply in a power cut, otherwise your battery inverter would be trying to power the entire neighbourhood. There would also be fireworks if the mains supply came back on after a cut and your home-made mains had drifted out of phase with the grid so you'd need some kind of soft synch before the two were linked together again. Not rocket surgery but very necessary.

I had rather assumed powerwall type installations would be designed only to support a few critical items (fridge/freezer, some lights, internet hub, maybe a couple of free sockets for stuff you decide you really need) and they'd be labelled to warn those might be live even when the power is off.

Martin Y wrote: Tue Jun 27, 2023 4:12 pm It makes sense that you'd need to isolate your house from the incoming mains supply in a power cut, otherwise your battery inverter would be trying to power the entire neighbourhood. There would also be fireworks if the mains supply came back on after a cut and your home-made mains had drifted out of phase with the grid so you'd need some kind of soft synch before the two were linked together again. Not rocket surgery but very necessary.

I had rather assumed powerwall type installations would be designed only to support a few critical items (fridge/freezer, some lights, internet hub, maybe a couple of free sockets for stuff you decide you really need) and they'd be labelled to warn those might be live even when the power is off.

Martin Y wrote: Tue Jun 27, 2023 4:12 pm
I had rather assumed powerwall type installations would be designed only to support a few critical items (fridge/freezer, some lights, internet hub, maybe a couple of free sockets for stuff you decide you really need) and they'd be labelled to warn those might be live even when the power is off.

Grumble wrote: Tue Jun 27, 2023 4:36 pm If your system is set up ok with a battery you won’t even see a flicker when a power cut happens
https://youtu.be/9xuleBA4Zcg

IvanV wrote: Tue Jun 27, 2023 8:11 pm

Grumble wrote: Tue Jun 27, 2023 4:36 pm If your system is set up ok with a battery you won’t even see a flicker when a power cut happens
https://youtu.be/9xuleBA4Zcg

He has Tesla batteries, which are designed to act as backup batteries, unlike batteries at half the price most of us will have. And he has to have 3-phase mains to have that large a solar/battery set up when he is in a thin part of the distribution system. That's extraordinary and a lot of money, that most people wouldn't put up with.

All the equipment lined up on that huge, clean, garage wall. Lovely if you can do that. Lovely to have such a wall at all, most of us don't.

I have a garage. Well, a garage-sized brick-built shed, as you can no longer access it with a car, the drive is too narrow for modern cars. But because it is detached from the house, and separated by a block-paved area, it was too much of a job to run cables back and forth from the garage to use the garage for housing the solar equipment, or even put some solar panels on its perfectly south-facing sloping roof. The annoyances of retro-fitting. The garage has an electricity supply, but that was put in when it was built, to replace an older garage, 15 years ago, and the block paving needed to be disturbed to some degree at that time. The supply cable between house and garage takes a really perverse and long route, to limit how much paving had to be lifted. And all my garage walls are already completely covered with various storage arrangements.