Looking to get solar panels

Raggs_2

Martyn1981 said:

Raggs_2 said:

Martyn1981 said:

Raggs_2 said:

Martyn1981 said:

Raggs_2 said:

There aren't shading issues.

Perhaps something to do with the DNO issues that were raised earlier? And having 2 inverters gets around that? The quote stays the same with the second inverter, so it hasn't changed from £6500 for 7.4kw. When I talk to them after the weekend I'll ask about just using a single inverter dual mppt though, does seem the cheaper option.

Hiya. I appreciate there aren't shading issues, that's why I said that would be the next option, if there were. I was just trying to cover all the options in an answer covering the difference between multiple strings and MPPT's, as the Solaredge kit is a different 'idea' again to those options. I've never suggested you have shading issues, but these threads are read by other people who may be considering PV, hence my covering that issue too.

For the DNO, two inverters would make it worse in your case as you said the panels will be on rooves with different orientations, south and west?

Two inverters would have to be sized for the peak of each roof, so for 3.7kWp, you'd want around 3.5kW inverters, giving a theoretical maximum export for the DNO of 2 x 3.5kW = 7kW. Obviously both systems wouldn't peak at the same time, but the DNO has to work with the inverter maximums, both of which will hit 3.5kW at times, just not the same time.

In reality, since both will not peak at the same time, and the west will be off max when the south peaks, and vice versa, you could get away with a single inverter of around 5.5-6kW.
This would all become irrelevant if the DNO is happy going up from 3.68kW to 7kW, but if they are not, then a lower compromise with the overall smaller single inverter would help you.

More importantly though, is that the single inverter will have more kWp to help it start up earlier, and run later, making it more efficient, and of course cheaper in the future to replace one inverter than two, given that so much of the cost will be for the engineer.

Apologies if this all seems petty or pedantic, but the suggestion of two inverters sounds incredibly odd to me*, and I truly believe that one would make for a simpler, cheaper and more efficient system for you. However, it's not the end of the World, and if the DNO say OK, then don't let my fine tunings spoil anything.

*I actually had two inverters originally on my ESE systems, that's because I have 13 small panels on the main roof with a 30d pitch and 5 large panels on the low roof at 20d pitch. At the time (when Solaredge was not well known) the installer (and myself) could not find a suitable inverter with dual MPPT that could cope, as their minimum voltage requirements only just matched the lower voltage from the 5 panel system, and the minimum voltage for the MPPTs was a bit higher than the panels could reach. So I had two smaller inverters, a 1.2kW (~92% efficient) and a 2.5kW (~94% efficient), I now have a single SE3500HD which is ~99% efficient.

Fair point on others reading!

Your points make sense on a single inverter, a single inverter does seem to make more sense.. The biggest thing for me though, is two or one, I'd need permission from the DNO first. And that applications can take upto 11 weeks. The company is trying to push me into installing at the start of September (they apparently have another job down here at the same time, so it would save them costs do so, so kindly offered to install the 2nd inverter at no extra cost...).  There's no way they could be sure of having permission by then.

Do all DNO's still operate this way? I assume so, can't see why the rules would have changed, given the grid hasn't been replaced.

Really appreciate the advice btw, please don't think I'm ignoring it etc, I just tend to question a lot to sort it out in my own head.

No probs, question away. The more you learn the better armed you will be when dealing with the companies.
In fact you've already spotted a small concern with them rushing you, that's always something to question. I'm not sure if the 'rule' still exists, or if it was a government or MCS rule, but installers were not supposed to start work for 14 days minimum, in order for customers to have more time to 'learn' and especially mull over the income side, which some installers would hype up with questionable claims.

In fact, my sister is getting a large install at the moment, and she had a good quote from a company that seemed 'good' to me. But one small thing kept niggling at me, and that was that the quote gave a very high return over 25yrs for leccy saved based on a compounded inflation rate of 8%. It may seem trivial, but I've pushed back against this carp for years, so encouraged my sister to hold on and get another quote, which came in yesterday a £1k cheaper and 480Wp larger.
I've just gone through the documents (between chatting with you) from the installer and they don't even bother stating financial returns, just an extremely accurate estimate of annual generation.

So you are right to question the niggles, don't ignore them.

This company so far seems better than the rest that have given me quotes. They used a 3% yearly increase in electricity prices, which doesn't seem too unreasonable.

I've had a company originally quote me a 3.6kW system + battery, then when they realised the chimney could be an issue, said we'll drop two panels, and use 370W panels, it'll be a bigger system (3.7) but also cheaper as we're using less panels... and then I'm sat there thinking "Well why the hell wouldn't you do that in the first place..." they also have an extremely high cost, along with using 7% inflation.

A second company calculating that I'm likely to use 80% of the energy produced on a nearly 6kW system, despite not having a battery, and also based it on me currently pay 16p per kWh, which obviously helps the sums look pretty. Also more expensive.

I'm not going to be pushed into installing on their timeframe. More questions to come I'm sure.

"Well why the hell wouldn't you do that in the first place..." LOL and a big thumbs up.
I think you have a pretty good grasp on things, and whilst PV has lots of little issues to learn, none are complex, and most are common sense.
Interestingly my sister's quote is also now for 370Wp panels. There's obviously a sweet spot, probably based on what is now being mass produced and shipped. I still recall getting excited at 280Wp and then 300Wp, but that's soooo 2010's now.

When I checked, the 370W were basically the same price as the 300W, using 300W looks like it's just clearing stock.

On that point, it looks like we'd be getting 2 inverters instead of 1 for that reason, they have them in stock, and it's cheaper for them to use them up, hence keeping to the budget we requested (though when he first gave me that system, it was only thinking about a single inverter, but I can understand it still perhaps working out cheaper for them).

I realise it's less than ideal, but how bad, real world, would it be to have 2 smaller inverters instead of 1 larger one? Twice as much to go wrong (do inverters fail often) but equally, if one fails, we don't lose the entirety of our production....

As for DNO's, he's told me that worst case scenario would be the DNO saying it can only export upto 3.7kW (3.68, whatever), and they will limit our maximum export amount. I'd guess this would sting a bit on very sunny days that we weren't using lots of power, but with some south and some west facing panels, would it actually cause us to lose that much revenue?

Dave_Fowler

If the DNO decide you have to limit output to 3.68kW it is easy to do if you have one inverter as most inverters have this limit available in their set-up screen.  But with two inverters I'm not sure how this can be done - especially if the inverters are working with panels on different orientations.  Can two inverters be made to talk to one-another so that their combined output is limited to 3.68kW?

Dave F

Raggs_2

Right, so it looks like we're going for 1 inverter with dual mppt. So no issue on limiting if needed. Not too panicked about how much income would be lost if we end up having to limit. I've asked what inverter it will be.

So final opinions! Deege Solar (anyone know them). 10 panels WSW facing roof. 7 panels on SES roof of home, and another 3 on SES facing garage roof.

£6500 inc VAT (5%).

1x Anti-bird netting (lots of birds here, don't want dead ones stuck under).
20 x Longi 370W LR4 60HPH panels. So 7.4kW.
1 x Inverter, single phase Dual MPPT (don't yet know final Wattage).
Roof fittings + Installation.

What do you all think? Good price? Worth going for?

Pile_o_stone

If I were the OP I'd insist that the PV Supplier installed an export limiting device:
https://www.sma-uk.com/solar-systems/export-limitation.html
This restricts the export to whatever the DNO decides (i.e. 3.68kw) but doesn't restrict the generation if it is actually being used. So if I had panels producing 8KW of power and wasn't using any it, then the export limiting device would reduce my generation down to 3.68. However, if I was boiling a kettle (3kw) and had my fridges, freezer and other items using a further 2kw, then the export limiting device wouldn't do anything as I was generating 8kw, using 5kw and exporting 3kw.

This is obv. much better than limiting the inverter to a maximum output of 3.68kw, no matter how much power I'm using.

Raggs_2

The inverter can limit the export itself (it states export limit, not production limit), at least that's how I read tech specs for similar inverters.

It's this one. 7.5kw dual MPPT. So a bit big for our 7.4kwh system, but not the end of the world I wouldn't think? 

http://www.sofarsolar.com/product-detail/463/SOFAR 7.5KTLM

Pile_o_stone

Raggs_2 said:

The inverter can limit the export itself (it states export limit, not production limit), at least that's how I read tech specs for similar inverters.

It's this one. 7.5kw dual MPPT. So a bit big for our 7.4kwh system, but not the end of the world I wouldn't think? 

http://www.sofarsolar.com/product-detail/463/SOFAR 7.5KTLM

Yes, the user manual states:
"C. Limiting the active power fed into the grid The inverter, if enabled can limit the amount of active power fed into the grid by the inverter to the desired value (Expressed as a percentage)."
Good to see this becoming available within the inverter, though I guess it only works if you have just the one inverter?

In my case, I have a 3.68 Inverter receiving FIT payments and a 1.5kw inverter not receiving FIT payments. If I added a further 2kw on my pergola, I'd need the separate export limiting device to monitor my total export and limit it to 5.18kw (which is my allowed limit). In reality I'd never get to that limit as my 4kw array is oriented East/West and so I rarely get beyond 2kw max, let alone 3.68.

Raggs_2

It would be a single inverter now.

The salesman has pushed, but then that's his job. Every time I've sent a question, they've had a genuine answer in my mind, and when needed, he's been willing to update it to fit (like going from 2 to 1 inverter). Pushiness from a salesman is not a surprise for me, and not something I'm going to feel aggrieved about.

Just sent an email to the council making sure there's no surprises for our property. There shouldn't be, but doesn't hurt to be careful!

Exiled_Tyke

Raggs_2 said:

It would be a single inverter now.

The salesman has pushed, but then that's his job. Every time I've sent a question, they've had a genuine answer in my mind, and when needed, he's been willing to update it to fit (like going from 2 to 1 inverter). Pushiness from a salesman is not a surprise for me, and not something I'm going to feel aggrieved about.

Just sent an email to the council making sure there's no surprises for our property. There shouldn't be, but doesn't hurt to be careful!

For me the trust would have gone by now and I'd be looking for alternatives. This is a huge investment and they are prepared to fob you off with solutions that are in their interests and not yours, and then attempt to justify them to a point.  This just isn't good enough. 

JKenH

Exiled_Tyke said:

Raggs_2 said:

It would be a single inverter now.

The salesman has pushed, but then that's his job. Every time I've sent a question, they've had a genuine answer in my mind, and when needed, he's been willing to update it to fit (like going from 2 to 1 inverter). Pushiness from a salesman is not a surprise for me, and not something I'm going to feel aggrieved about.

Just sent an email to the council making sure there's no surprises for our property. There shouldn't be, but doesn't hurt to be careful!

For me the trust would have gone by now and I'd be looking for alternatives. This is a huge investment and they are prepared to fob you off with solutions that are in their interests and not yours, and then attempt to justify them to a point.  This just isn't good enough. 

That’s better than my recent experience. I have been looking to extend my PV and possibly add a battery. I’ve had two quotes but when I enquired about an alternative arrangement that might work better for me I failed to get any response from either installer. I might just give up and stick with what I’ve got as I am well into the zone of ever diminishing returns. 

Exiled_Tyke

JKenH said:

Exiled_Tyke said:

Raggs_2 said:

It would be a single inverter now.

The salesman has pushed, but then that's his job. Every time I've sent a question, they've had a genuine answer in my mind, and when needed, he's been willing to update it to fit (like going from 2 to 1 inverter). Pushiness from a salesman is not a surprise for me, and not something I'm going to feel aggrieved about.

Just sent an email to the council making sure there's no surprises for our property. There shouldn't be, but doesn't hurt to be careful!

For me the trust would have gone by now and I'd be looking for alternatives. This is a huge investment and they are prepared to fob you off with solutions that are in their interests and not yours, and then attempt to justify them to a point.  This just isn't good enough. 

That’s better than my recent experience. I have been looking to extend my PV and possibly add a battery. I’ve had two quotes but when I enquired about an alternative arrangement that might work better for me I failed to get any response from either installer. I might just give up and stick with what I’ve got as I am well into the zone of ever diminishing returns. 

I used a company in West Yorks ( who do travel quite far afield but I don't know how far if its a relatively small job) for my battery. We put up two extra panels to qualify for VAT relief and to give me some morning sun (obviously no FIT there).  I'm pretty sure what didi isn't 'quite' financially viable but am very happy with what we agreed in the end. I found them very amenable to my suggestions and happy to answer my queries - I was particularly concerned about making sure the Old SE and the new microinverters all integrated appropriately with the battery, generation meters etc..