Solar Panels UK - is it worth it?

[Mrklaw]

seems a few more places willing to quote. Got one from Fortis (never heard of them but they’re MCS and trustpilot seems ok). 400w x 10 (4kw), fox ESS solar inverter, givenergy AC3.0 Ac coupled battery inverter, givenergy 9.5kw battery.

Basically same spec as Eon. Eon had quoted £10800 back in May last year, Fortis quoting £11500 and able to install in the next 6 weeks (although I’d need them to take Eon’s DNO approval but they are transferrable it seems)

Tempted just to get things moving - would lose the 0% finance but we can pay from savings and pay that back so not a big deal.


thoughts? Alternative would be Otovo as mentioned earlier but I’m wary as they seem to think a hybrid inverter won’t work to allow my existing array to charge the battery. Maybe I could go to the next stage or ask to talk to someone more technical there as prices seemed ok. But this new one is givenergy whihc I’d researched befoer and can go outside and have reasonable controls over, rather than growatt

 

[barry.perfect]

Not sure if this is the right place to ask, but does anyone know how the Tesla Powerwall App calculates its "Energy Value" on the Impact Page?

This, I believe, is what Tesla thinks you have saved by having the Powerwall and Solar.

It says it considers solar and peak to off-peak offset from charging at cheap rate and using the energy during peak rate, but I cannot seem to get any numbers I actually record to come anywhere near to what the Tesla App shows.

 

[WannabeOwner]

Mine ALSO shows exactly £73 for 03-Apr - 09-Apr. I'll eat my had if we both have the same install and sunshine!! My solar generation for that week was 434kWh ...

 

[YYY2022]

I am intrigued as to how it calculates this too. Mine seems to be a simple calculation of my solar generation multiplied by my peak usage rate. That week shows £64 - my solar generation was 184kWh for that week and my peak rate is currently 35.05p.

Not really what I understood it was supposed to show but the week before works out on the same basis too. My understanding was that it should take account of total home and grid usage, imports/exports and load shifting. Mine seems to be a somewhat more simple calculation!

This basis wouldn't seem to fit for Wannabe though with solar generation of 434kWh unless you have a very inexpensive peak import rate.

 

[WannabeOwner]

unless you have a very inexpensive peak import rate

I don't have interest in the calculation, so don't bother to maintain my tariff rates accurately, but in case helpful they are set to:

Off Peak £0.20 buy and £0.03 sell
Peak £0.40 buy and £0.03 sell

 

[barry.perfect]

I don't have interest in the calculation, so don't bother to maintain my tariff rates accurately, but in case helpful they are set to:

Off Peak £0.20 buy and £0.03 sell
Peak £0.40 buy and £0.03 sell

Mine is
off peak £0.10 buy, sell £0.01
peak £0.44, sell £0.01

Tomorrow I will have a go at putting my attempt at how I calculate the saving, based on
- Solar Generated
- Export to Grid
- Off Peak House Usage
- Off Peak Draw from Grid
- Peak House Usage
- Peak Draw from Grid

All from the Powerwall. That I think can/could be used by the Tesla App to calculate the saving, but doesn’t seem to make sense to me, but may make sense to others

 

[barry.perfect]

Mine is
off peak £0.10 buy, sell £0.01
peak £0.44, sell £0.01

Tomorrow I will have a go at putting my attempt at how I calculate the saving, based on
- Solar Generated
- Export to Grid
- Off Peak House Usage
- Off Peak Draw from Grid
- Peak House Usage
- Peak Draw from Grid

All from the Powerwall. That I think can/could be used by the Tesla App to calculate the saving, but doesn’t seem to make sense to me, but may make sense to others

OK here goes, here is my man maths on what the actual saving was for the week the Powerwall said I saved £73, be gentle with me, I suspect I am missing something obvious...

1. Solar Saving: Generated 166.85 kWh - Exported 23.17 kWh = 143.68 kWh * Peak Cost £0.44 = £63.86 (don't think this is controversial?)

2. Offsetting of Peak Saving: Peak Used by house 254.2 kWh - Peak Drawn from Grid 4.42 kWh - Solar Used (from above, assumes solar is all in peak time) 143.68 kWh = 106.1 kWh * Peak Cost £0.44 = £47.15

3. Offset of Off Peak Saving: Off Peak Used by house 179.9 kWh - Off Peak Drawn from Grid 166.61 kWh = 13.29 kWh * Off Peak Cost £0.10 = £1.33

4. Export Saving: Export 23.17 kWh * Export Rate £0.01 = £0.23 (although I don't get paid for export, but the Tesla App only accepts £0.01 as the smallest value)

So I make the saving £63.86 + £47.15 + £1.33 * £0.23 = £112.57

Phew, if anyone made it this far, thank you

I think 1 and 4 are fairly straightforward, but not so sure about 2 and 3, anyone got any thoughts?

£112.57 is very different to £73.

As you probably guessed I am trying to track my payback progress...

 

[WannabeOwner]

1. Solar Saving: Generated 166.85 kWh - Exported 23.17 kWh = 143.68 kWh ...

My CALC for that element is complicated by the charging of the cars (2x Tesla).

As far as PowerWall / APP is concerned that is "House" usage. (It can presumably see the cars, just doesn't (as far as I am aware) have any ability to include that in the "savings" SUMs.

I suppose I could take the view that if it came off the PV and didn't get exported its "A saving". But my PV can generate enough (peak) to charge both cars at 7kW ... so that usage is significantly different to the house!

As you probably guessed I am trying to track my payback progress...

Would Last year's kWh MINUS this year's do? (For each tariff ...).

 

[barry.perfect]

My CALC for that element is complicated by the charging of the cars (2x Tesla).

As far as PowerWall / APP is concerned that is "House" usage. (It can presumably see the cars, just doesn't (as far as I am aware) have any ability to include that in the "savings" SUMs.

I suppose I could take the view that if it came off the PV and didn't get exported its "A saving". But my PV can generate enough (peak) to charge both cars at 7kW ... so that usage is significantly different to the house!



Would Last year's kWh MINUS this year's do? (For each tariff ...).

Agree on charging the car from Solar, it is probably just offsetting what I would have charged on off peak electricity, rather than peak, unless of course I could not have charged the car enough in the off peak, but that is pretty rare.

As far as comparing with last year, I think I have changed so much in that time that a comparison probably won’t work, I.e. tariff changes, extra person in the house, gas heaters replaced with electric ones etc. But I will take a look and see how it compares to my other calculations.

 

[WannabeOwner]

I think I have changed so much in that time that a comparison probably won’t work,

Yes, inevitably that makes a comparison difficult. I just take the viewpoint that I am now saving 80% of my annual electricity bill (for an investment of £X ) regardless of what the price of electricity may be over the next 20-ish years. I see it as the equivalent of an investment which is tax-free and index-linked

Other Man Maths formulae are available!

 

[Drew57]

Other Man Maths formulae are available!

Mine was "spend £xk to be almost off-grid and write it off rather than leave it to the kids"

Ideally we'll leave them just the house and spend the rest.... my wife is certainly on a mission to do so.

 

[Pete UK]

Hi,

Just about to firm up my install and was wondering….

Does anyone have any real world experience of the difference between N-cells compared to P-cells (and PERC). Perhaps you had a different array with N-cells added later on recently?

Looks like I’ll be getting Jinko Tiger Neo N-Type full black 420kW panels. I think they are half-cut (?) but it doesn’t specifically say on the spec. They look pretty good on paper though.

I’ve read all the specs and googled reviews a lot but I’m only coming up with ‘less degradation’, ‘HOT2’ technology and the standard manufacturers blurb. Apart from the reduced degradation etc, do they work better in lower light etc? Or is it all just a lot of hype/ sales pitch?

Any info welcomed. Thanks.

 

[Chimpy McChimp]

Kudos to everyone here's deep knowledge and research of solar panels. I'm awaiting mine being installed but my research stopped at
1. I could cut my electricity usage by around 30% on average. And
2. Interest free loan from Scottish government.

After that I decided to go for it!!

I suspect once I'm all installed and up and running I'll be back to try and understand more!!!

 

[spon88]

Hi,

Just about to firm up my install and was wondering….

Does anyone have any real world experience of the difference between N-cells compared to P-cells (and PERC). Perhaps you had a different array with N-cells added later on recently?

Looks like I’ll be getting Jinko Tiger Neo N-Type full black 420kW panels. I think they are half-cut (?) but it doesn’t specifically say on the spec. They look pretty good on paper though.

I’ve read all the specs and googled reviews a lot but I’m only coming up with ‘less degradation’, ‘HOT2’ technology and the standard manufacturers blurb. Apart from the reduced degradation etc, do they work better in lower light etc? Or is it all just a lot of hype/ sales pitch?

Any info welcomed. Thanks.

We've got 24 of those on our roof - even E/W split.

They look and perform very well and are highly rated. They are half-cut is my understanding but them I believe most decent brands are these days.

Today has been relatively cloudy and raining a good proportion of the time but we've still managed 13 kwh. This should go over 20 kwh by the end of the day even if it doesn't brighten up. When it was bright a week or so back we broke 50 kwh and were regularly doing 35 - 40.

We've been seeing up to 4.9 kwp on the east array and well in excess of 5 on the west array so far this year. Best max generation so far this year was around 7.8 kwp.

I'm no panel expert but I did do some research and those Jinko ones looked more than decent. They're working well for us.

 

[Pete UK]

We've got 24 of those on our roof - even E/W split.

They look and perform very well and are highly rated. They are half-cut is my understanding but them I believe most decent brands are these days.

Today has been relatively cloudy and raining a good proportion of the time but we've still managed 13 kwh. This should go over 20 kwh by the end of the day even if it doesn't brighten up. When it was bright a week or so back we broke 50 kwh and were regularly doing 35 - 40.

We've been seeing up to 4.9 kwp on the east array and well in excess of 5 on the west array so far this year. Best max generation so far this year was around 7.8 kwp.

I'm no panel expert but I did do some research and those Jinko ones looked more than decent. They're working well for us.

Excellent news. Thanks for your time replying really appreciate it. Glad they are working out well for you.

 

[googlepeakoil]

Excellent news. Thanks for your time replying really appreciate it. Glad they are working out well for you.

I've got 7.8kW of panels. One of the best things I ever bought!
I got 4kw of LG 14x285's originally on the FIT - which is now in year 7 and giving me about £1k a year now.
I then got another inverter and 11x 325's 2 years ago. + a home battery I've since upgraded to 12.7kWh usable.
My electricity bill DD is currently £5 because I went £100s in credit and then got the £67 discounts. Made about £55 with the Octopus "pay to turn off" scheme over christmas! Spring to Autumn I get enough extra electric that I get free hot water via a Solic 200. For 6 months of the year I have enough extra excess to charge the M3 SR+ for the 5000 miles a year I do. I also have a warm water fish tank that uses 5kWh a day! I'd do EVEN better if my panels weren't mostly shaded for 4 months of the year!
Solar is bloody brilliant!!! Amazing that you can now get 425w panels that aren't that much bigger than my 285's. Shop around - should be able to get 6kW solar and 10kWh storage from about £11k. I used GoingGreenRenewables for my original install, and again for my upgraded solar + upgraded battery - based about 30 miles West of London. Great small company. The battery system I got was an Alpha ESS.
FYI - If your roof is partly shaded during 10-6pm then that will really kill the output unless you get micro inverters - but micro-invertering your panels will add £1k to the quote at least. Don't trust Tigo optimisers - they're a pile of sh** and don't do anything!

 

[DaveNN]

OK here goes, here is my man maths on what the actual saving was for the week the Powerwall said I saved £73, be gentle with me, I suspect I am missing something obvious...

1. Solar Saving: Generated 166.85 kWh - Exported 23.17 kWh = 143.68 kWh * Peak Cost £0.44 = £63.86 (don't think this is controversial?)

2. Offsetting of Peak Saving: Peak Used by house 254.2 kWh - Peak Drawn from Grid 4.42 kWh - Solar Used (from above, assumes solar is all in peak time) 143.68 kWh = 106.1 kWh * Peak Cost £0.44 = £47.15

3. Offset of Off Peak Saving: Off Peak Used by house 179.9 kWh - Off Peak Drawn from Grid 166.61 kWh = 13.29 kWh * Off Peak Cost £0.10 = £1.33

4. Export Saving: Export 23.17 kWh * Export Rate £0.01 = £0.23 (although I don't get paid for export, but the Tesla App only accepts £0.01 as the smallest value)

So I make the saving £63.86 + £47.15 + £1.33 * £0.23 = £112.57

Phew, if anyone made it this far, thank you

I think 1 and 4 are fairly straightforward, but not so sure about 2 and 3, anyone got any thoughts?

£112.57 is very different to £73.

As you probably guessed I am trying to track my payback progress...

Not got around to throwing in my PVs yet.
Scaffolders are now holding me up.
However, by load shifting ( I.O) and using my 3 x 3000 pylontechs, I'm averaging under 11p per kwhr.
Not too bad.

 

[Mrklaw]

finally got someone else to get me panels installed and hopefully in May. Emailed Eon to tell them to sod off (but can I please get a copy of the G99 they apparantly said was approved). 9 months of being ghosted and fobbed off is enough thanks.

Paying about £700 more for the same spec and no 0% finance but I don’t want to miss another summer

 

[Pete UK]

I've got 7.8kW of panels. One of the best things I ever bought!
I got 4kw of LG 14x285's originally on the FIT - which is now in year 7 and giving me about £1k a year now.
I then got another inverter and 11x 325's 2 years ago. + a home battery I've since upgraded to 12.7kWh usable.
My electricity bill DD is currently £5 because I went £100s in credit and then got the £67 discounts. Made about £55 with the Octopus "pay to turn off" scheme over christmas! Spring to Autumn I get enough extra electric that I get free hot water via a Solic 200. For 6 months of the year I have enough extra excess to charge the M3 SR+ for the 5000 miles a year I do. I also have a warm water fish tank that uses 5kWh a day! I'd do EVEN better if my panels weren't mostly shaded for 4 months of the year!
Solar is bloody brilliant!!! Amazing that you can now get 425w panels that aren't that much bigger than my 285's. Shop around - should be able to get 6kW solar and 10kWh storage from about £11k. I used GoingGreenRenewables for my original install, and again for my upgraded solar + upgraded battery - based about 30 miles West of London. Great small company. The battery system I got was an Alpha ESS.
FYI - If your roof is partly shaded during 10-6pm then that will really kill the output unless you get micro inverters - but micro-invertering your panels will add £1k to the quote at least. Don't trust Tigo optimisers - they're a pile of sh** and don't do anything!

Good to hear.

My roof is very non-optimal, small south facing area, different height’s, more area to the north and a lot to the east with bits of shading. I’m quite interested in how much can be generated by atmospheric reflection on non-sunny days. Would it be like 5%, 10% of max or what? And what type of conditions produce this situation. Overcast? Hazy? Or what?

What happens if an optimiser fails?
Does the whole panel go dead or just the optimiser stops optimising? Or does it depend, what part of the optimiser fails?

Cheers.

 

[googlepeakoil]

Good to hear.

My roof is very non-optimal, small south facing area, different height’s, more area to the north and a lot to the east with bits of shading. I’m quite interested in how much can be generated by atmospheric reflection on non-sunny days. Would it be like 5%, 10% of max or what? And what type of conditions produce this situation. Overcast? Hazy? Or what?

What happens if an optimiser fails?
Does the whole panel go dead or just the optimiser stops optimising? Or does it depend, what part of the optimiser fails?

Cheers.

Not got any optimisers. Only Tigo's which don't work like those - don't seem to help my shading issue!
You can have panels just facing straight up and you'll get 50-60% of the ideal orientation. Yesterday with white clouds and no sun beaming through I was still doing 3kW off my 7.7kW - and bare in mind I've never seen more than 6.5kW. You can generate 25% of the rated power even off the panels facing the wrong way - especially if the sky is white clouds as the light is bouncing all around.
Google for "solar graph for orientation" and you'll see that facing North and you'll still get about 30% of due south. But 30% isn't much. You'll get about 70% for East or West. If the roof is at a low pitch like 20 degrees it'll do better if it's North facing.
Sounds like you should fill to the South as much as possible. Then the East, avoid the North. Check the measurements of the different panels - some vary. Old size was 1.6x1m. But most now are 1.9x1.1 or 2.1x1.1 - remember they're not supposed to fit them closer than 30cm to an edge - but most will go closer. Matters more if you're in a wind exposed area. The greatest issue is not the weight but the uplift if they stick above the roofline. You want to work out the best way to get as many as possible on the south roof. And make sure you get black framed panels. The silver framed look rubbish in comparison. Get black back-sheet as well if you're worried about what they look like. Black-on-black is going to look better than black-on-white if they're in an odd layout.
I was lucky - I've got 22 panels on a SW facing roof. 4 panels on a NE facing roof for some morning sun.

You could look at micro-inverters if you've got some that are going to be shaded when others aren't. Micro-inverters are guaranteed for 20 years I think.