Solar Panels?

[Jambo85]

jrb43 said:

OutInTheShed said:

I've known people get too obsessed with 'using everything they generate'.

You should dry your clothes when it's convenient and go and do something nice on a sunny day.
Or, if you're at home on a sunny day, put your washing on the line!

This. Otherwise we've regressed as a civilisation to the point just before fire was invented and all daily activities were governed by the position of the sun?

You’re both right but for us to make continued progress on net zero then demand shifting will be essential. It is one of the reasons the government dropped FITs, to encourage self consumption and thus shifting load away from peak times.

Most of us do have bigger things to worry about though which is why it makes sense to use technology to automate this - e.g. my new tumbledryer will sit and wait with wet clothes in it until it gets a signal from the web to start (or x hrs elapsed, whichever comes first). In theory all I need to do is connect the MyEnergi and Miele APIs to some home automation software and tell it to switch on the dryer when I have excess PV generation. Obviously for the average punter this needs to be seamless and work out of the box.

Also - I’ll repeat it as I think it’s at least a few pages since I mentioned it - anyone considering a battery, consider an immersion heater diverter instead, and put your dishwasher on hot feed if it’ll take it. Much less outlay.

[TriumphStag3.0V8]

Jambo85 said:

pingu393 said:

TriumphStag3.0V8 said:

pingu393 said:

I was told that if you get a battery that isn't a Tesla, you will only be able to store energy. You won't be able to export to the grid. Any excess will just be wasted. Tesla batteries cost almost twice other batteries, and have a 12 month lead time.

You were told wrong. With a battery (any battery) you store the electricity that would otherwise have been exported to the grid. Once the battery is full, if the electricity will then go to the grid unless it has somewhere else to go:
For example - mine sends any excess production to the battery, then to an electric car charger (I don't have an EV but did have the charge point installed for future use), and then to an immersion heater controller, so once the battery is full, and the car is full, and the hot water is at temperature, then it will export to the grid.

One thing the Tesla powerwall does permit (at least certain models of it) is for the house to remain powered in the event of a power cut - the electricity companies do not like people putting 240v back down the wires whilst engineers might be working on them (!). So most systems cut off if the house power goes. The Tesla has a switching capability built in which allows the house to be isolated from the grid to stay live. I believe this type of system needs specific notification/approvals.

The alternatives that I was given were Solax or Tesla. I was told that Solax couldn't export to the grid. I may have misunderstood.

I think TS misunderstood your post.

I'm not sure I did, he said that you could only export electricity to the grid if you had a Tesla battery. This is not the case, unless I have misunderstood something else?

Edited by TriumphStag3.0V8 on Saturday 18th February 19:26

[Jambo85]

I think he (or the person informing him) means discharging the battery into the grid, but it’s not only Tesla who have this feature either.

I’m not so sure on re-reading though

Edited by Jambo85 on Saturday 18th February 19:49

[TriumphStag3.0V8]

Jambo85 said:

I think he (or the person informing him) means discharging the battery into the grid, but it’s not only Tesla who have this feature either.

I’m not so sure on re-reading though

Edited by Jambo85 on Saturday 18th February 19:49

I think that the Solex can actually discharge into the grid! Can't think of a single instance of why anyone would want to mind you. Possibly someone with a more creative mind will be along shortly with an idea.

Edited by TriumphStag3.0V8 on Saturday 18th February 20:06

[pingu393]

Jambo85 said:

I think he (or the person informing him) means discharging the battery into the grid, but it’s not only Tesla who have this feature either.

I’m not so sure on re-reading though

Edited by Jambo85 on Saturday 18th February 19:49

I was told that Tesla can discharge into the grid, and it's the only one that can. As I said, I may have been misinformed, or misunderstood.

It could be that the other battery on offer (a Solax) can't discharge to the grid, and I understood the comments as "no other battery" could discharge to the grid.

[loskie]

maybe we should just chat about Subaru WRC's and Integrales

[OutInTheShed]

pingu393 said:

I was told that Tesla can discharge into the grid, and it's the only one that can. As I said, I may have been misinformed, or misunderstood.

It could be that the other battery on offer (a Solax) can't discharge to the grid, and I understood the comments as "no other battery" could discharge to the grid.

Batteries don't discharge into the grid, inverters do.
So there is tech out there which can take a generic battery and feed into the grid.
There is experimental data from Nissan Leaves feeding the grid.

But discharging from a battery via whatever tech to the grid is mostly pointless, because the cycle life of the battery tends to mean it's costing you nearly as much as you're getting paid, just in battery depreciation.
This may not be true if you can get paid a stout rate for short term surges in demand.
The market is immature and will look different before many people's battery has paid for itself.

[Jambo85]

TriumphStag3.0V8 said:

I think that the Solex can actually discharge into the grid! Can't think of a single instance of why anyone would want to mind you. Possibly someone with a more creative mind will be along shortly with an idea.

With time of use billing it is conceivable that it would be advantageous to store your peak solar generation around midday and then sell it into the 6-7pm peak for a higher price. Or charge at 2am from the grid and sell back at 6am.

Whether the suppliers will ever give consumers the price differentials to make that profitable while paying off the investment required is another question though, and clearly you’d need enough battery capacity to cover your own needs plus excess.

[gazapc]

Jambo85 said:

TriumphStag3.0V8 said:

I think that the Solex can actually discharge into the grid! Can't think of a single instance of why anyone would want to mind you. Possibly someone with a more creative mind will be along shortly with an idea.

With time of use billing it is conceivable that it would be advantageous to store your peak solar generation around midday and then sell it into the 6-7pm peak for a higher price. Or charge at 2am from the grid and sell back at 6am.

Whether the suppliers will ever give consumers the price differentials to make that profitable while paying off the investment required is another question though, and clearly you’d need enough battery capacity to cover your own needs plus excess.

There were quite a few periods last year when Octopus Agile Outgoing had very good export rates available. Easily 50+ pence. Although it is one thing making a bit extra money, a different basing an investment payback on it. Data here:

https://www.energy-stats.uk/octopus-agile-outgoing...


Also the idea that force discharge is limited to only two brand options is not correct, off the top of my head both sunsync and givenergy inverters both can also do this and have integration with Octopus.

[dobly]

Our inverter is made by Fronius, and can export electricity stored in the Powerwall back to the grid if we have such a surplus of production over the house load, which includes the (electric only) hot water cylinder up to a maximum rate of 5kW.

[Flooble]

Speaking of inverters - how long do they last? I am sure I heard they were usually the first thing to go, and also one of the most expensive bits. Now that "micro-inverters" are favoured by some, is that storing up lots of future expense at about the point where the panels would reach break-even?

[pingu393]

Jambo85 said:

With time of use billing it is conceivable that it would be advantageous to store your peak solar generation around midday and then sell it into the 6-7pm peak for a higher price. Or charge at 2am from the grid and sell back at 6am.

Whether the suppliers will ever give consumers the price differentials to make that profitable while paying off the investment required is another question though, and clearly you’d need enough battery capacity to cover your own needs plus excess.

This is what Octopus Flux is offering. Tesla Energy Plan is now dead.

https://octopus.energy/smart/flux/

For my postcode...

	Import Rate	Export Rate
Day rate	32.81p / kWh	22.9p / kWh
Flux rate (02:00 - 05:00)	19.68p / kWh	9.12p / kWh
Peak rate (16:00 - 19:00)	45.93p / kWh	36.68p / kWh

Standing charge 44.12p / day

[Uncle boshy]

Ambleton said:

Just had a quote from Octopus today on their scheme.

10x 395W JASolar panels supposedly "high efficiency"
5.2kWh GivEnergy battery
GivEnergy Invertor - not sure on size, assume 3.6kW

Circa £10.5k including scaffolding, installation, commissioning everything. (East Midlands)

I suspect the 5.2kWh battery should be big enough for our needs. Work during the day so most of our energy usage is evenings/weekends although that might change in about 6m as my wife is pregnant.


Annual usage is estimated to be about 3000kWh.

I guess the unknown for me is.... How much will I still rely on the grid? Would this system provide 50% of my consumption? 75%? 100%?

Edited by Ambleton on Thursday 16th February 23:07

I'm about 100 miles south of you, so figures may be slightly better but here's some real world info from the last 6 months of a a 5kw system (14 panels)

gross production 2585Kw, of which I've used 52% and exported 1372

for me that means 38% self sufficiency, but that's varied from 69% in July down to 15% in Dec

not bothered with a battery

I'm on octopus agile outgoing, average price received has been £0.26 per kWh over the last 6 months, lowest month was 9p per kWh, highest was 37p per kWh.


I'd do the maths separately for battery and panels as you may find the payback time reduces by removing the battery from your calculations. For me adding a battery made the payback worse, but everyone's situation is different

[Ambleton]

That's really useful thanks.

Using these figures makes an easier calculation too.

3.9kWp system. No battery
Energy used through the year = 2990kWh
Energy created by panels = 3025kWh
Energy SOLD to the grid = 818kWh × 26p/kWh = £212.60
Energy BOUGHT from the grid = 783kWh × 34p/kWh = £ £266.11

Meaning net electric bill would be ~£54. A saving of ~960/anum

Solar panels only are ~£8k. So a repayment period of about 8.3yrs.

[KTF]

This has prompted my to revisit the quote I had from Octopus and run the numbers again.

I can work out the ROI with no export/import:

3.16 kW system. No battery
Energy used through the year = 2154kWh (my figures)
Energy created by panels = 2363kWh (Octopus quote figures)
£8143 installed

At the current rates on the capped energy price (34.23p) my annual consumption of 2154 will cost £893.43 a year (energy of £737.31 plus standing charge of £156.11.

Taking the standing charge off (I would still have to pay it) I am looking at £737.31 x 11 years to cover the cost of the panels only which puts me off.

Thats before I have factored in the sold and bought quantity so how have you worked that out or is there a tool online that can be used? There must be something other than guesswork?

Edit: Putting my figures in to this tool (looks like one of the better ones) it says: https://great-home.co.uk/solar-export-guarantee-se...

Energy used: 2,154.0 kWh
Solar generation: 2,363.0 kWh
Purchased from grid: 1,243.2 kWh
Energy Exported (SEG): 1,451.9 kWh

Bill without solar/battery £732.36
Bill savings: -£309.66
Export Payments (SEG): -£217.79 (15.00p per kWh)
Total annual benefit -£527.45
New bill £204.90

Payback (years): 15.2
Total Investment: £8,000

I am still struggling to see how the numbers make economic sense yet all around me are houses with scaffolding going up ready for solar installs.

Edited by KTF on Monday 20th February 14:58

[Jambo85]

Uncle boshy said:

I'm about 100 miles south of you, so figures may be slightly better but here's some real world info from the last 6 months of a a 5kw system (14 panels)

gross production 2585Kw, of which I've used 52% and exported 1372

for me that means 38% self sufficiency, but that's varied from 69% in July down to 15% in Dec

not bothered with a battery

I'm on octopus agile outgoing, average price received has been £0.26 per kWh over the last 6 months, lowest month was 9p per kWh, highest was 37p per kWh.


I'd do the maths separately for battery and panels as you may find the payback time reduces by removing the battery from your calculations. For me adding a battery made the payback worse, but everyone's situation is different

Your gross production seems quite low, over three years I have averaged over 2600 kWh per year with a 3.6kWp system which is split east/west. North of Aberdeen.

[OutInTheShed]

KTF said:

....

Thats before I have factored in the sold and bought quantity so how have you worked that out or is there a tool online that can be used? There must be something other than guesswork?

Unless you can predict the weather for the next 10 years, there will be an element of guess work.

If you want to do a better job of guessing, set up a spreadsheet and break down your year.

In January, you might expect say 10 sunny days when you'll generate xkW which are useful, ykW which you export and you'll import zkW
The other 21 days will have a different x y and z

repeat for the other 12 months, different ratio of sunny days, different x y and z each time.

You need to have a fair idea of how you use your electricity, not just 3,000 kW a year, but month by month and day/evening/night.

You can get a fair idea of the variations of power from this website:
https://www.newquayweather.com/wxsolarpv2017.php
If anyone has similar data, please share it!

The thing to do IMHO, is to not try to guess all those x y and z's exactly but to be fairly sure they are in a range.
Then you can be reasonably confident your total x y and z's or the year will be between certain values.

Then you can look at tariffs and estimate the range your bills and saving lie in.

IF you start looking at battery systems, you can move some y into z, but that will vary by the day/month etc.


Key thing to know is that there are a lot of 'tumble drying on a sunny afternoon' nutjobs out there, claiming they are saving more than a sensible person was paying in the first place.

[Jambo85]

OutInTheShed said:

Key thing to know is that there are a lot of 'tumble drying on a sunny afternoon' nutjobs out there, claiming they are saving more than a sensible person was paying in the first place.

[NMNeil]

KTF said:

I am still struggling to see how the numbers make economic sense yet all around me are houses with scaffolding going up ready for solar installs.

Edited by KTF on Monday 20th February 14:58

Simple, because electricity costs won't come down, they will only get more expensive.
Think about it; a utility company has 1 million customers each paying $xx.xx a month for electricity with all the associated fees, taxes and compulsory charities.
Now imagine if only 5% of those customers install solar systems and home batteries it means a big reduction in profits for the utility, yes it's offset by lower generating costs because they save on the cost of fuel to generate less power, but they still have to maintain the infrastructure. How will they make up for the financial loss of those 5%?, by raising prices of course, and then more people will get fed up with high power bills and invest in solar. Rinse and repeat.
https://www.pewresearch.org/fact-tank/2022/10/14/h...

[Arnold Cunningham]

This has reminded me to send a chaser to our solar lot.