Looking to get solar panels

Martyn1981

Raggs_2 said:

Martyn1981 said:

Sorry for any pedantry, but crucial to understand that two strings is fine if the two sets of panels match, so same number orientation, pitch etc. But if there is any difference between the two strings, then the inverter will need to have multiple MPPT's not just multiple strings.
To further complicate it, you can of course have both, such as inverters with 2 MPPT's, and 1 + 1 strings, or 2 + 1 strings, or 2 + 2 strings feeding those MPPT's.
So best combo is one inverter with 2 (or 'dual') MPPT's, for two non identical strings, and if there is any shading on a string(s), then a Solaredge inverter with power optimisers, which should still be cheaper (and far more efficient) than two inverters.

Solaredge inverters only seem to go upto 6kw for the single phase. That's not going to be sufficient for a 7.4kw system right? I know you aim for a bit under, but that seems significantly under?

I can see that I can purchase (from a wholesaler so I assume without vat) a 3.3kw single phase single mppt inverter for £383, even a second one is going to be significantly less than 20 solaredge micro inverters/optimizers and a £900 6kw solaredge inverter.

I presume they'll link the West facing 10 panels to one inverter, and the south facing 10 to the other.

Hi. The 6kW model would probably be OK, but there are also 8kW and 10kW models. I think Solaredge is worth the money, if there are shading issues, as I mentioned.*
For two roof aspects you simply get a dual MPPT inverter which will be far cheaper and simpler to install than two inverters.

*Obviously you can find two cheap inverters that would be less than a Solaredge package, but if the rooves have shading then you need to compare the Solaredge kit to two expensive inverters with high quality shade management for a fair comparison.

Edit - Just to be clear, and going back to your earlier post:

Not sure on the ettiquette here, but going to post again. Just received a mail saying we'll require 2 inverters given the size, normally an extra £750, but they'll waive it if we install on a range of days when they'll already be down (yeah right, I'm not getting rushed if I'm not happy).
Is 2 inverters better than 1?

two inverters are not better than one. The only reason I can see to offer you this 'deal' is if they have two inverters hanging around that they want to get rid off, otherwise they would reduce the install time (a cost to them) and install one larger inverter (less cost to them).

Raggs_2

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.

Martyn1981

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.

Raggs_2

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.

gefnew

Hi  Raggs_2
This maybe of interest

Martyn1981

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.

Raggs_2

Sorry, I'm not really sure what I'm supposed to be looking at? Obviously different inverter setups. Showing the extra benefits of 1 vs multiple I presume.

gefnew

Hi 
The input i put in was for a 7.2kw system to see what the difference was between different inverter set ups
if you look at the blue circles on the right it shows only two full circles that will give you the most production.
one with single inverter and one two inverters it was just a quick thing for you see.
maybe mart could throw more light on it.
Regards

Raggs_2

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.

Martyn1981

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.