Solar Panels UK - is it worth it?

[RagingWhisky]

Has anyone used the designer at SunnyDesignWeb?

I found it useful to prove that rather than use the 8 x 390W panels I was quoted for, I could, in theory, bump up the max kWp for my roof by ~20% by squeezing in 4 x 545W and 4 x 405W panels.

View attachment 810864

It let me create 2 zones and identify the obstacles - roof windows and the dormer in 2D or 3D and with/without the map behind.
This is a lot easier than printing out the 2D roof map from the quote and then manually using a ruler to see what bigger panels would fit!
It also seems to take into account the shading for the obstacles so that should help calculate a more accurate yield.

The rest of the designer does have some limitations for amateur tinkering about with:
- only has their own inverters etc. included (which is fair enough)
- has EUR for the costs (this can be changed but not to GBP!) but I don't suppose it matters

But it does try to help with Design Suggestions such as for the inverter(s):-
View attachment 810866

Though I'm too thick to understand fully what it is suggesting yet - still working on it.

That looks like a great site to play around with!

One thing i'm surprised on, is that its completely discounting your dormer as "dead zone" ?

If you do jump into the solar 'twilight zone' definitely speak with your installer on install options for the dormer - I got funny looks, but they did it for myself (single panels on dormer approach) and it legitimately added good quality energy generation. You've got some good potential to pickup from east/west/south-ish sun, so not to be discounted!

 

[swainson08]

Any advice on a quote that I’ve received for solar and a battery would be appreciated.

Quoted for a 6kw system, south facing 35 degree roof and a 6kw battery. £15k all in.
To be, seems expensive but I’m no expert.

Many thanks

 

[RagingWhisky]

Any advice on a quote that I’ve received for solar and a battery would be appreciated.

Quoted for a 6kw system, south facing 35 degree roof and a 6kw battery. £15k all in.
To be, seems expensive but I’m no expert.

Many thanks

Prices will be fluctuating like mad (higher pricing more often than not...), so can't speak to the accuracy, but i'd be expecting a higher mix of panels and/or batteries for 15K, but then it all depends on 'what panels' and 'what batteries' and any other extras tucked in.

Some scenarios both myself and colleagues looked at (with actual quote numbers) from start of 2022

1. £8918: 24 panels (405watt) + 6kWh inverter (PV only - no batteries)
2. £14,600: 24 panel, 6kWh inverter (for pv to 'everything in home') + 10.4kWh battery+6kWh inverter (power into the home <-> batteries)
3. £13,212: 17 panels+5kWh inverter, 10.4kWh battery+5kWh inverter
4. £18,983: 24 panel, 6kWh inverter (for pv to 'everything in home') + 17,5kWh battery+6kWh inverter (power into the home <-> batteries)+EPS+MyEnergi units (eddi/harbi/hub)

All includes respective mounting, g99/g100 and MCS certification.

No guarantee those prices would exist anymore, but its at least a set of datapoints.

 

[Avendit]

Any advice on a quote that I’ve received for solar and a battery would be appreciated.

Quoted for a 6kw system, south facing 35 degree roof and a 6kw battery. £15k all in.
To be, seems expensive but I’m no expert.

Many thanks

Yep, seems high, but process are in the moment. My 22x375w panels+ 10kwh battery are around £13k.

 

[Liquidv]

Don't forget to add bird protection and Tigo optimisors!

 

[RagingWhisky]

Don't forget to add bird protection and Tigo optimisors!

Good call on the bird protection....i've not done it with mine, and just seeing which way the fates take me!

Can imagine like a lot of installs, bird protection escaped the mind!

Worst case, after migration seasons are over you get someone with a ladder and brave enough to put up netting/grates retroactively...or just go 'eh screw it'

 

[PITA]

Good call on the bird protection....i've not done it with mine, and just seeing which way the fates take me!

Can imagine like a lot of installs, bird protection escaped the mind!

Worst case, after migration seasons are over you get someone with a ladder and brave enough to put up netting/grates retroactively...or just go 'eh screw it'

You only need bird protection if you have Rock Pigeons (Feral Pigeons)... the ones with Green/Purple shiny necks. They are hole seekers and very territorial. Will nest under panels and cause a right mess. The type you see in town centres.

If you have Wood Pigeons (like we have)... the ones with White necks. These nest in trees & bushes, and are not interested in getting under your panels. Our Wood Pigeons will sit on the roof... walk up and down... but never go under the panels.

 

[simmotech]

Don't forget to add bird protection and Tigo optimisors!

The SMA website I mentioned earlier had a 4 min video showing a software solution in its inverter, SMA ShadeFix, that it claimed outperformed most hardware optimizers for shade management. It also refers to 'bypass diodes' and MPP.

If I understand, then a string of panels' output is limited to the one with the lowest output so if one panel is in shade, then the rest are virtually in shade too.
An optimizer is used to get around this and produce the best overall MPP.
Bypass diodes are built into panels so they can split a single panel into 'modules' (3 in video) and bypass a 'module' if it is in shade but the other modules on the panel aren't.
SMA ShadeFix does this by somehow forcing one or more bypass-diodes into conduction so all non-shaded panels can run at full power and shaded panels contribute their non-shaded modules' power. It says it can do this without needing communication just choosing the highest MPP for the array.

So is my understanding roughly correct?
What is really best - hardware or software?
And, if hardware, is Tigo the best optimizer?

 

[simmotech]

One thing i'm surprised on, is that its completely discounting your dormer as "dead zone" ?

I'm not against this but I'm only working on estate agent photos/google maps currently.
It seems a no-brainer that if £800 scaffolding is going up for a job, it make sense to put up as many panels as possible.

This rotated view seems to indicate it would be possible but how would they be linked in?
Extra 545W panels on the Blue zone?
Extra 405W panels on the Green zone?
Or would they have to be in their own string? And do inverters generally support 3 strings or is 2 the maximum?
Would the optimizers mentioned in other posts ensure that they don't reduce the MPP from the main panels block when they are not sun facing?

 

[btc1k]

Any advice on a quote that I’ve received for solar and a battery would be appreciated.

Quoted for a 6kw system, south facing 35 degree roof and a 6kw battery. £15k all in.
To be, seems expensive but I’m no expert.

Many thanks

I just paid £14700 for 16 panels, 6.2kw system, across a South and a West roof, with a Powerwall 2 (13.5kwh).

 

[94jdh]

Any advice on a quote that I’ve received for solar and a battery would be appreciated.

Quoted for a 6kw system, south facing 35 degree roof and a 6kw battery. £15k all in.
To be, seems expensive but I’m no expert.

Many thanks

In normal times, 1k per 1kW solar and 1k plus £400/kW battery - so in your case 6k for solar and £3.4k for battery ( 9.4k total).
However as previously be mentioned, demand and availability have been pushing up prices over 25% so favours the installer at the moment.
Try and get a minimum of another 2-3 quotes if possible.

 

[YYY2022]

My panels are being installed in 5 weeks and cost £5.8k for 14 x 370w panels (5,180kwp).

Powerwall is due to arrive in January next year (was originally hoping November) and cost £8.2k, so 14k all in.

All ordered in March. South facing install.

 

[Alset2go]

I have JOJU Solar coming around tomorrow for final survey..Although I have had an initial quote I will let you know what the final outcome is for optimising my roof with panels and Powerwall system.Best wishes to all.

 

[RagingWhisky]

I'm not against this but I'm only working on estate agent photos/google maps currently.
It seems a no-brainer that if £800 scaffolding is going up for a job, it make sense to put up as many panels as possible.

View attachment 810978

This rotated view seems to indicate it would be possible but how would they be linked in?
Extra 545W panels on the Blue zone?
Extra 405W panels on the Green zone?
Or would they have to be in their own string? And do inverters generally support 3 strings or is 2 the maximum?
Would the optimizers mentioned in other posts ensure that they don't reduce the MPP from the main panels block when they are not sun facing?

We had ours akin to "10 panels east" / "14 panels west" - where the respective 'east'/'west' roof their own array.

Both arrays going to a single inverter is fine (so long as its sized accordingly, and of good enough quality that your 'start-up' efficiency isn't losing you out of free generation (more power from the sun needed to kick it to life vs migro-inverters per panel etc). In fairness, our split is akin to 4kWh and 6kWh respectively in the arrays and the inverter happily kicks in without any functional loss/issue.

So for you, it'd be akin to "green zone dormer" if following that kind of approach for array split, then whichever PV inverter approach best works for your use cases > "inverter for PV to home elec", "Inverter for PV to home elec+batteries" or "inverter for PV to home elec + secondary inverter for home elec to battery" etc. (Pros and cons to each, so worth a shout with your installer for your particular generation/needs).

One thing I would say is if you look at that south-east facing dormer for your 'green zone' don't discount your north-west facing dormer, as though it's not going in the advertised 'ideal' you would still likely get a good healthy few hundred watts in peak late afternoon/early eve from the setting sun (a good counter-balance to those green-zone panels that may face the shade from the dormer).

 

[Avendit]

We had ours akin to "10 panels east" / "14 panels west" - where the respective 'east'/'west' roof their own array.

Both arrays going to a single inverter is fine (so long as its sized accordingly, and of good enough quality that your 'start-up' efficiency isn't losing you out of free generation (more power from the sun needed to kick it to life vs migro-inverters per panel etc). In fairness, our split is akin to 4kWh and 6kWh respectively in the arrays and the inverter happily kicks in without any functional loss/issue.

So for you, it'd be akin to "green zone dormer" if following that kind of approach for array split, then whichever PV inverter approach best works for your use cases > "inverter for PV to home elec", "Inverter for PV to home elec+batteries" or "inverter for PV to home elec + secondary inverter for home elec to battery" etc. (Pros and cons to each, so worth a shout with your installer for your particular generation/needs).

One thing I would say is if you look at that south-east facing dormer for your 'green zone' don't discount your north-west facing dormer, as though it's not going in the advertised 'ideal' you would still likely get a good healthy few hundred watts in peak late afternoon/early eve from the setting sun (a good counter-balance to those green-zone panels that may face the shade from the dormer).

Yep - run the math and solar is super simple more is more! Panels facing different directions stretch your generation window to cover more baseline. They may not hit their ideal generation numbers, but like @simmotech said, if you are paying for the labour and scaffold then the incremental for more panels is only really a design challenge as each panel is only £200 each.

@simmotech it looks like those dormers might complicate the electrical side a bit, depends if you were already going micro inverter per panel, or if you were thinking 2 strings for the 2 sizes of panels. Having multiple sizes and 3 different facings would probably need micro inverters tho! I'm not sure you would get more than 1 panel on each side of the dormer which may start to impact the looks of the array and the acceptance factor from the rest of the family.

 

[Avendit]

Or would they have to be in their own string? And do inverters generally support 3 strings or is 2 the maximum?
Would the optimizers mentioned in other posts ensure that they don't reduce the MPP from the main panels block when they are not sun facing?

My proposed 8kw inverter has 2 'MPPT' which are the bits of tech that do all the hard work balancing an array and getting the best generation they can. One takes one string, but the other is setup to accept 2 strings, but those 2 strings have to be balanced - ie on the same roof with the same angles, panel count and ideally shadding. Its just a multiplier to get it up to the advertised wattage really - the 3rd string doesn't add the flexibility you might hope for.

Optimisers come in 2 forms it seems there was the device mentioned a few posts back along side the bird protection, but you can also move to micro inverters where each panel has its own inverter that maximises that 1 panel's output. I'm guessing there is a cost implication of this, but I've not investigated.

 

[WannabeOwner]

I'm thinking of add some West panels (my house orientation would mean they are West North West ...) because its disappointing to see the Solar stopping in the evening - I rarely get 1kW after 18:50 in May, and 2kW after 18:00

 

[Avendit]

I'm thinking of add some West panels (my house orientation would mean they are West North West ...) because its disappointing to see the Solar stopping in the evening - I rarely get 1kW after 18:50 in May, and 2kW after 18:00

You are much further south than us, but a couple of sunny days this month I was looking at what our expected output in the evening might be. We will have 14 SW facing panels and the roof is in full sun through to about 10pm at this time of year, but generation is also only about 1kw through 6-7pm. As I say, further north (and panels facing more south), but the power just wanes right off as the sun lowers. A lovely evening doesn't generate much unfortunately.

Will be interesting to see how the reality matches up with the theory in a months time.

 

[WannabeOwner]

A lovely evening doesn't generate much unfortunately.

Yes, good point thanks. I think I read somewhere that a good morning is more frequent than a good evening ?

I expect I could use my East South East panels, in the morning, as a guide as to what the West ones would achieve in evening ... although my East is more South and my West more North (obviously!)

They start at 5AM (but basically "nothing useful").

Plenty of 1kW days starts at 06:20

Plenty of 2kW days starts at 06:40

Quite a fast ramp up (now I look at it) between 06:20 and 06:40

Dunno what the Evening equivalent of 06:20 would be (for West facing panels) [what with British Summer Time and so on] compared to the slow-down that I currently see (my South panels on separate roof doing most work I expect) [from above: I rarely get 1kW after 18:50 in May, and 2kW after 18:00]

 

[Avendit]

Yes, good point thanks. I think I read somewhere that a good morning is more frequent than a good evening ?

I expect I could use my East South East panels, in the morning, as a guide as to what the West ones would achieve in evening ... although my East is more South and my West more North (obviously!)

They start at 5AM (but basically "nothing useful").

Plenty of 1kW days starts at 06:20

Plenty of 2kW days starts at 06:40

Quite a fast ramp up (now I look at it) between 06:20 and 06:40

Dunno what the Evening equivalent of 06:20 would be (for West facing panels) [what with British Summer Time and so on] compared to the slow-down that I currently see (my South panels on separate roof doing most work I expect) [from above: I rarely get 1kW after 18:50 in May, and 2kW after 18:00]

Have aplay on pvwatts? Start by modelling existing set up to check it all matches, then start playing to get the potential new panels. Use the CSV export and apivot table to explore the evening outputs.