Solar Panels?

Author
Discussion

Chris Type R

8,018 posts

248 months

Friday 3rd February 2023
quotequote all
NMNeil said:
Understood, but I chose my panels on weight and dimensions as I was getting them up a ladder and onto the roof on my own. Even with the relatively smaller and lighter 250 watt panels I used it was still an absolute sod of a job.
I plan on trying this for my next array - https://secondlifestorage.com/index.php?threads/ea...

I know what you mean about size - the roof space for my next array (E & W) is limited - I need just the right size. Still hoping to fit in 21/22% efficiency panels.

Ambleton

6,646 posts

191 months

Thursday 16th February 2023
quotequote all
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.

Roof is SE facing. 3bed detached late 80s early 90s house. Today we've used 6.7kWh. we've used between 55-60kWh every week this yr so far.

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%?

The lady I spoke to today said that the battery charges during the day from, then as we use the energy in the evening the battery will deplete, and then can be set so it only charges up on the low overnight rate. Ready for the mornings.

Edited by Ambleton on Thursday 16th February 23:07

dobly

1,168 posts

158 months

Thursday 16th February 2023
quotequote all
^if I were you I would put more solar panels up (if there is room) and upgrade both the inverter and battery if at all possible, going with a MyEnergi libbi system which is modular (in terms of battery size) - you may be limited by the proposed 3.6kW inverter,, go for 5kW to futureproof a bit.
You should be able to produce most if not all of your needs on a good day in summer, but in winter you may only generate 5% - it just depends on the weather. That’s the difficult thing with solar - theoretically you should be able to generate x percentage of your usage on average, but the weather and local conditions one year may change that by quite a bit. This is where a larger system comes in - you should be able to produce a bit more in ideal conditions and store some of it to help smooth out the troughs.
But of course you will be putting more cash in upfront to do this…

Edited by dobly on Thursday 16th February 23:40


Edited by dobly on Thursday 16th February 23:41

Ambleton

6,646 posts

191 months

Thursday 16th February 2023
quotequote all
I can ask for an update for say a 12 panel system or more. The next battery up is 9.5kWh battery so could get that priced too.

In reality though I still don't fully understand WHAT that means in terms of usage or impact on bills.

pingu393

7,719 posts

204 months

Friday 17th February 2023
quotequote all
In my experience, everything is 25% less efficient than quoted. We have solar panels rated at 3.9kW. That means the current would be over 16A. It will never be this because there are losses during the DC to AC conversion, and in the inefficiencies of the system. The best we have had is around 12A.

We do generate more than we use. Yesterday, we exported 7.26kWh and imported 5.66kWh.

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.

dobly

1,168 posts

158 months

Friday 17th February 2023
quotequote all
nb caveat that I live on the other side of the planet in southern New Zealand (it is summer here)

We have just had a solar system installed - switched on one week ago in fact.
We have 15 400w panels, split 7/8 on an east/west roof, a 5kW inverter and a Tesla Powerwall 2 with Tesla Gateway. If MyEnergi was available here we would have gone with their products, as the libbi battery scale-ability looks great to me. We will get an eddi, as they are being tested for importation in the next few months - when they are NZ approved / available, and possibly a zappi if and when we get an EV...
We placed the order at the end of Nov 22, so some 12 weeks ago.
On clear blue sky days were were filling the battery up each day, as well as exporting some to the grid, and powering the house (including hot water - we have no gas and our HWC is our biggest user). On cloudier days such as yesterday we still topped the battery up quite a bit and reduced our grid import to just a few kWh.
It will be a different story later in the year obviously.

All the electricity that we are fed from the grid is renewable - there are some massive hydro plants as well as loads of wind turbines in our part of the country, but the electricity isn't cheap, hence why we are generating our own. Whether we get our money back in reasonable time is open to question, but I can't see the grid electricity getting cheaper ever...


Ambleton

6,646 posts

191 months

Friday 17th February 2023
quotequote all
Interesting. I kind of wrongly assumed then that ~12.5k worth of solar and batteries would essentially delete our electric bill... Sounds like not then


Elysium

13,756 posts

186 months

Friday 17th February 2023
quotequote all
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.

Roof is SE facing. 3bed detached late 80s early 90s house. Today we've used 6.7kWh. we've used between 55-60kWh every week this yr so far.

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%?

The lady I spoke to today said that the battery charges during the day from, then as we use the energy in the evening the battery will deplete, and then can be set so it only charges up on the low overnight rate. Ready for the mornings.
The panels are stated in kWP which is the 'typical' output in factory conditions.

You will yield about 850kWh/kWP depending on location. So a 3.95kWp install will generate 3358kWh per annum. About the same as you use.

Obviously you only get that during the day and you get a lot more in the summer than the winter.

Unfortunately, you need a lot more energy in the winter than in the summer. Plus it sounds like you are out for most of the day.

The battery helps to solve this, but you will still be importing most of your energy in the winter and exporting most of the PV generation in the summer.








Edited by Elysium on Friday 17th February 09:58

KTF

9,788 posts

149 months

Friday 17th February 2023
quotequote all
Ambleton said:
Interesting. I kind of wrongly assumed then that ~12.5k worth of solar and batteries would essentially delete our electric bill... Sounds like not then
I also had a quote from Octopus (a page or so back) and was under the same impression as yourself.

As solar is not the magic bullet I also thought it would be, I parked the quote and wont be proceeding. I think I calculated it as 10+ years before the cost was recovered which put me off.

Gazzab

21,061 posts

281 months

Friday 17th February 2023
quotequote all
KTF said:
Ambleton said:
Interesting. I kind of wrongly assumed then that ~12.5k worth of solar and batteries would essentially delete our electric bill... Sounds like not then
I also had a quote from Octopus (a page or so back) and was under the same impression as yourself.

As solar is not the magic bullet I also thought it would be, I parked the quote and wont be proceeding. I think I calculated it as 10+ years before the cost was recovered which put me off.
Surely it’s one useful consideration still? Eg panels, batteries, cheap overnight electricity, insulation etc as a package? I am also looking at ‘electric wallpaper’ (I have 20+ft tall ceilings). Whilst the payback might not work when looking at utilities savings as your measure, it may work better if you include an increase in your properties value. I suspect I could increase my house price by quite a few grand if it has had a comprehensive and sensible set of improvements.

Jambo85

3,311 posts

87 months

Friday 17th February 2023
quotequote all
Gazzab said:
KTF said:
Ambleton said:
Interesting. I kind of wrongly assumed then that ~12.5k worth of solar and batteries would essentially delete our electric bill... Sounds like not then
I also had a quote from Octopus (a page or so back) and was under the same impression as yourself.

As solar is not the magic bullet I also thought it would be, I parked the quote and wont be proceeding. I think I calculated it as 10+ years before the cost was recovered which put me off.
Surely it’s one useful consideration still? Eg panels, batteries, cheap overnight electricity, insulation etc as a package? I am also looking at ‘electric wallpaper’ (I have 20+ft tall ceilings). Whilst the payback might not work when looking at utilities savings as your measure, it may work better if you include an increase in your properties value. I suspect I could increase my house price by quite a few grand if it has had a comprehensive and sensible set of improvements.
It is useful, but whether it pays itself back in a reasonable timeframe is the usual sticking point, particularly if there’s any chance of a house move within 10ish years.

If you want to do it for green warm fuzzy feelings and the desire to tinker with newish tech, that’s different (that’s how I justify it).

Gazzab

21,061 posts

281 months

Friday 17th February 2023
quotequote all
Jambo85 said:
Gazzab said:
KTF said:
Ambleton said:
Interesting. I kind of wrongly assumed then that ~12.5k worth of solar and batteries would essentially delete our electric bill... Sounds like not then
I also had a quote from Octopus (a page or so back) and was under the same impression as yourself.

As solar is not the magic bullet I also thought it would be, I parked the quote and wont be proceeding. I think I calculated it as 10+ years before the cost was recovered which put me off.
Surely it’s one useful consideration still? Eg panels, batteries, cheap overnight electricity, insulation etc as a package? I am also looking at ‘electric wallpaper’ (I have 20+ft tall ceilings). Whilst the payback might not work when looking at utilities savings as your measure, it may work better if you include an increase in your properties value. I suspect I could increase my house price by quite a few grand if it has had a comprehensive and sensible set of improvements.
It is useful, but whether it pays itself back in a reasonable timeframe is the usual sticking point, particularly if there’s any chance of a house move within 10ish years.

If you want to do it for green warm fuzzy feelings and the desire to tinker with newish tech, that’s different (that’s how I justify it).
You missed my point. My house will be worth more after the work. Will pay for itself. Maybe.

loskie

5,144 posts

119 months

Friday 17th February 2023
quotequote all
but only if you plan on selling it? And then only if you reinvest the money in a cheaper house.

Gazzab

21,061 posts

281 months

Friday 17th February 2023
quotequote all
loskie said:
but only if you plan on selling it? And then only if you reinvest the money in a cheaper house.
I plan on selling my house at some point - it’s too large for me for the long term.. Reinvesting has nothing to do with its value.

Ambleton

6,646 posts

191 months

Saturday 18th February 2023
quotequote all
I've done a bit more maths today. And its absolutely FULL to the brim with assumptions. So bare with me.

The solar system I've been quoted is:
3.95kW of panels, 5.2kWh battery.

Let's say that actually generates 2950kWh/annum (75% efficiency)

Over the year let's say that's divided up into spring (25%) summer (35%), autumn (25%), winter (15%)

That means per season that generates...
Spring = 737.5kWh
Summer = 1032.5 kWh
Autumn = 737.5kWh
Winter = 442.5kWh

Our energy usage looks more like.
Spring = 750kWh
Summer = 700 kWh
Autumn = 750kWh
Winter = 800kWh

That means that of the 2950kWh being generated
2617.5kWh is actually being used
333kWh are being exported TO the grid

Additionally, 362.5kWh are being purchased FROM the grid

Standing charge doesn't change regardless as it still needs to be connected to the grid.

The system costs circa £10500.

Let's say long term, energy prices rise at 10% per year and they start at 50p/kWh. Let's also assume that feed in rates are 1/3rd the value of exporting. Over 6yr time period

No solar
6yrs of 3000kWh/annum = £11573

Vs (with solar)
6yrs of 362.5kWh/annum = £1398 (export)
MINUS
7yrs of feed in 333kWh = £428 (feed in)
PLUS
£10500 (solar panels and battery installation)
Total = £11470

So IF energy prices do continue to rise at 10%/anum (big IF) AND the feed in rates are 1/3d of export rates, AND my assumptions about efficiency and power generation are there or there abouts, then it starts to net zero at 6yrs.

gazapc

1,319 posts

159 months

Saturday 18th February 2023
quotequote all
pingu393 said:
In my experience, everything is 25% less efficient than quoted. We have solar panels rated at 3.9kW. That means the current would be over 16A. It will never be this because there are losses during the DC to AC conversion, and in the inefficiencies of the system. The best we have had is around 12A.

We do generate more than we use. Yesterday, we exported 7.26kWh and imported 5.66kWh.

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.
Am I missing a whoosh parrot? If not, this post is mostly rubbish.

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.

Roof is SE facing. 3bed detached late 80s early 90s house. Today we've used 6.7kWh. we've used between 55-60kWh every week this yr so far.

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%?

The lady I spoke to today said that the battery charges during the day from, then as we use the energy in the evening the battery will deplete, and then can be set so it only charges up on the low overnight rate. Ready for the mornings.

Edited by Ambleton on Thursday 16th February 23:07
1) get some more quotes as seems a little expensive
2) if getting Givenergy kit make sure it is generation 2. The previous gen1 hybrid inverters have a lower max charge/discharge rate.
3) when comparing solutions make sure you consider depth of discharge (DOD). The Givenergy stuff is nameplate at 100% DOD, so 5.2 kWh usable . Others nameplate higher, but you can only use 80 or 90% of the capacity.
4) yes you can charge overnight on a cheap rate during winter (many different inverters can do this)
5) assuming you are maxed out on panels, you can consider the next size battery up. My consumption is similar and I'm having 9.5 kWh installed in the next few weeks. But it is easier to upgrade that in the future if needed.

Does Octopus not provide a forecast of your self consumption with the quote? You can use that to work out how much total you are saving.

Ambleton said:
Over the year let's say that's divided up into spring (25%) summer (35%), autumn (25%), winter (15%)

That means per season that generates...
Spring = 737.5kWh
Summer = 1032.5 kWh
Autumn = 737.5kWh
Winter = 442.5kWh
You can use this tool to estimate your monthly production.
https://re.jrc.ec.europa.eu/pvg_tools/en/

Edited by gazapc on Saturday 18th February 01:06

AW10

4,422 posts

248 months

Saturday 18th February 2023
quotequote all
Ambleton said:
I've done a bit more maths today. And its absolutely FULL to the brim with assumptions. So bare with me.

The solar system I've been quoted is:
3.95kW of panels, 5.2kWh battery.

Let's say that actually generates 2950kWh/annum (75% efficiency)

Over the year let's say that's divided up into spring (25%) summer (35%), autumn (25%), winter (15%)

That means per season that generates...
Spring = 737.5kWh
Summer = 1032.5 kWh
Autumn = 737.5kWh
Winter = 442.5kWh

Our energy usage looks more like.
Spring = 750kWh
Summer = 700 kWh
Autumn = 750kWh
Winter = 800kWh

That means that of the 2950kWh being generated
2617.5kWh is actually being used
333kWh are being exported TO the grid

Additionally, 362.5kWh are being purchased FROM the grid

Standing charge doesn't change regardless as it still needs to be connected to the grid.

The system costs circa £10500.

Let's say long term, energy prices rise at 10% per year and they start at 50p/kWh. Let's also assume that feed in rates are 1/3rd the value of exporting. Over 6yr time period

No solar
6yrs of 3000kWh/annum = £11573

Vs (with solar)
6yrs of 362.5kWh/annum = £1398 (export)
MINUS
7yrs of feed in 333kWh = £428 (feed in)
PLUS
£10500 (solar panels and battery installation)
Total = £11470

So IF energy prices do continue to rise at 10%/anum (big IF) AND the feed in rates are 1/3d of export rates, AND my assumptions about efficiency and power generation are there or there abouts, then it starts to net zero at 6yrs.
IMHO your assumptions are too skewed in favour of panels and a battery.

As a rule of thumb panels will reduce your import by 1/3 and a battery by a further 1/3.

Current leccy rates are closer to 34p for import and 6-p for the SEG.

At some point your battery is going to start losing capacity. And can you really discharge it to zero? You thus have to factor in its replacement cost and/or the loss of capacity.

This might come across as doom and gloom but I have yet to see a scenario where panels and a battery for a “normal” household at current-ish system and electricity rates have a payback period that isn’t around the 10 year point unless there’s cheap rate (less than 10p per kWh) overnight charging of the battery. Happy to be shown otherwise; would be delighted to put panels on our 13x8m south facing roof 1 mile from the Channel and vaporise our 5000kWh annual electricity bill but I just can’t make the numbers add up.

Ambleton

6,646 posts

191 months

Saturday 18th February 2023
quotequote all
gazapc said:
You can use this tool to estimate your monthly production.
https://re.jrc.ec.europa.eu/pvg_tools/en/
I'm probably being dumb, is Azimuth essentially the direction the solar panels will be facing?

IE, the roof surface has a bearing of 109.7degs SSE.

If yes, then 180 should yeild the best result, but it appears that zero does, hence my confusion.

Ambleton

6,646 posts

191 months

Saturday 18th February 2023
quotequote all
AW10 said:
IMHO your assumptions are too skewed in favour of panels and a battery.

As a rule of thumb panels will reduce your import by 1/3 and a battery by a further 1/3.

Current leccy rates are closer to 34p for import and 6-p for the SEG.

At some point your battery is going to start losing capacity. And can you really discharge it to zero? You thus have to factor in its replacement cost and/or the loss of capacity.

This might come across as doom and gloom but I have yet to see a scenario where panels and a battery for a “normal” household at current-ish system and electricity rates have a payback period that isn’t around the 10 year point unless there’s cheap rate (less than 10p per kWh) overnight charging of the battery. Happy to be shown otherwise; would be delighted to put panels on our 13x8m south facing roof 1 mile from the Channel and vaporise our 5000kWh annual electricity bill but I just can’t make the numbers add up.
All this is kinda what I'm trying to get to the bottom of. Clearly at the the minute it doesn't represent a great investment. Otherwise everyone would be doing it.

If it represents a net recovery in say 7-8yrs then it makes sense of you want to be more self sufficient and use less from the grid and not to worried about making money, so long as you don't lose money.

But if after 7-8yrs you're in a hole of several thousand pounds then it can really only be treated as a hobby.

Currently my electricity is...

44.17p/kWh daytime rate
16.61p/kWh night time rate
Octopus Outgoing is 15p/kWh on fixed at the moment.

Edited by Ambleton on Saturday 18th February 08:39

AW10

4,422 posts

248 months

Saturday 18th February 2023
quotequote all
Ambleton said:
Currently my electricity is...

44.17p/kWh daytime rate
16.61p/kWh night time rate
Octopus Outgoing is 15p/kWh on fixed at the moment.
OK, stoopid question alert - why is your rate not capped at 34p? Is it because you have elected to have a tariff that has a cheap night time rate? If that's the case how are you currently making use of the cheap night time rate?