4kw system?.

Spats

Thanks guys, good comments, I appreciate what you are saying. 

It helps me a lot to understand how the system works and how to move forward.

Much appreciated. 

Heedtheadvice

Must admit I do not know why you are so worked up about this, Spats.

You have learned now there is more to it than the headline figure and you have been supplied by an installer that maybe could have explained better. You were however given all the important information regarding your expected generation. If you do not exceed that 3200kWh over a year you might have a justifiable grouse.

Not specifically aimed at you but for readers who may be in a similar position if they do not read threads like this and then know better what they are buying...in rather simplistic terms and probably poor analogies!

It is a little like buying a "100w" led light bulb. It is not 100w (that is the incandescent approx equivalence). The real spec is the light output in lumens,  but people do not as a norm measure that output and rely on the box label.

In this case the panels have the label giving potentially 4kWp /on rare occaissions/.

The issue is that supplied is an inverter that has a label that shows it conforms to DNO regulated limitations, it was not explained ( to you spats in this case) that you have to apply to exceed that level to attach to the grid.

You buy a car that will drive at 90m.p.h. but are still restricted to 70mph on roads (through your own action rather than automatically). You need to pass a test to thus drive .........but you do not need a test to have installed solar PV generation. Your MCS installer takes care of this for you.

Tis a shame if this wasnot explained but I doubt many of us would bother making an application to exceed the nominal DNO limit for a few watts eextra.....nor send a light bulb to a calibration agency to ensure the light output meets spec!

Spats

@Heedtheadvice I have read what you say but the question is: -

1) Why did the Company quote me for a 4kw system, and on the quote was for a 4kw inverter.

When it came to installing the system, i was under the impression it was still a 4kw inverter being installed.

After it was installed in the beginning of July and we had that glorious weather, it did not peak at 4kw using the monitor, as that was the system i had payed for, then and only then did i check the inverter which was 3.6kw.

2) Why didn't the Company explain it's a 4kw system, but we are only going to supply a 3.6 kw inverter because of the output being  3.68 kw.

It would have made sense to tell the customer exactly what they are buying and getting, not buy one thing and get something different.

Company's that sell these systems should explain to the customer exactly what they are getting and why. 

Heedtheadvice

You have very good points!

I had not picked up that your quote was for a 4kW inverter too. Your installer really has been, so it would seem,  sold you short on both explanation and supply, that being the case.

arty688

Yes they should of explained that a '4KW system' means around 4kw of panels(under lab conditions) coupled with a 3.6kw inverter. I assume you detailed quote would say what kit you were getting and how much generation to expect. The fact is a bigger inverter would generate less so what you have is the most efficient system combination. So I'm not sure what you are after from the company ?

Martyn1981

Spats said:

After it was installed in the beginning of July and we had that glorious weather, it did not peak at 4kw using the monitor, as that was the system i had payed for, then and only then did i check the inverter which was 3.6kw.

Just to make sure there is no confusion, even if you'd had a 4kW inverter, I doubt you'd have seen 4kW in July. In the summer, when air temps are higher, and there's less wind, you'd be lucky to see 90%, probably more like 85%, and during that heat wave it would have been less.

My system is E/W so a bit more complicated, but it can sustain about 4.2kW in late June and early July from around 11am to 3pm, in perfect conditions. This year it was holding about 3.2kW as the temps were so, so much higher.

You'll probably (I need to caveat a bit) only see 100% in the summer, if the air is cool, perhaps some sunshowers, and the sun goes behind a cloud, then when it pops out, the panels are cooler, and you get some cloud edge lensing, you may see 100% for a few seconds, before the panel temps rise quickly, and generation drops back down to 90% or less.

You may see 100%+ in April and October, if it's a gloriously clear sky, cold temps, and then perhaps for a couple of mins, before panel temps rise, and generation drops again.

This may sound strange, but had you come on here and said that you were getting a 4kWp system and a 4kW inverter, myself, and many other PV'ers would have advised you against it, and suggested you ask the installer for a 3.6kW(ish) inverter, and a few quid off the price.


With regard to the confusion you've experienced by not seeing 4,000W(ish) on your monitor, I totally understand, and of course then the fear kicks in that you've been diddled (oh er misus!), but the good news is that you appear to have the best set up for your circumstances, whether done deliberately, or simply to save the installer a few quid on their quote.

It's also a good thread for others to read, either as peace of mind for why their system does what it does, or as an aid for them when accessing quotes for future systems.



PS - Purely for fun, and to throw a cat amongst the pigeons, you may want to check the specs on line for your PV panels. I suspect their ratings will carry a 0% to +5% caveat. Back when I got mine in 2011, they typically had a -5% to +5% rating, so think of that as a bonus. 

Heedtheadvice

I have looked back and it would have been good if you had shown your quote with 4kWp panels and for the 4kW inverter. All water under the bridge as far as the thread is concerned.

In practical terms you have had what would normally be called  4kWp system installed even though for a variety of reasons you will probably never (even with a 4kW inverter) generate a peak power of 4kW. As has been mentioned the key element in terms of output is the annual output and you probably have the best system to maximise that.

As has already been suggested you must decide what you now want.

Taking it as read the quote was for a 4kW inverter you could have a case for forcing a change to one of that max power but likely to be less efficient. A lot of agro potentially for a poorer resultant perfomance?...or look for compensation and that might be a fight you might not win so a risk there. Install not strictly to the letter of the quote but better performance installed than the quote?

Or possibly just put it down to experience, regarding the company and the technical aspects, accept you will be generating annually more than what a change of inverter might give you and feel good about all that generation.

arty688

I would be surprised though if you detailed quote didn't say what panels and inverter they were going to install? The quotes I have so far which were before survey stated this so I can't see how the final quote after the survey wouldn't tell you exactly what you were getting.. As you may have wanted to investigate the panels and inverter before install. Didi you get more than 1 quote?

Spats

arty688 said:

I would be surprised though if you detailed quote didn't say what panels and inverter they were going to install? The quotes I have so far which were before survey stated this so I can't see how the final quote after the survey wouldn't tell you exactly what you were getting.. As you may have wanted to investigate the panels and inverter before install. Didi you get more than 1 quote?

Description of Goods

PV 4KW INVERTER WITH WIFI STICK(monitored)

BLACK JA SOLAR PANELS 330W MONO

FITTING KIT AND BIRD GUARD

DELIVERY

Cable, Protection and Auxiliary Equipment

Description of Services

GDGC INSURANCE

LABOUR

MCS CERTIFICATION  from the original quote I signed. As you can see that is the quote with prices and company omitted. pictures is what I took. It was never mentioned at any time it was going to be a 3.6 kw inverter, if it was mentioned and I agreed i would never have posted in the forum. so you can understand my frustration that the company did this behind my back.

Heedtheadvice

Hmmm, a very poor quote in that it is unspecific and can kead to different interpretations.

One of which you reasonably made that it would be a PV 4kW inverter. That may or may not have been correct.

You now have accept that what you got was in fact ok and gives you a better performance or consider what your options are. I do not think this thread is going to help withn the latter, it is up to you. No point in repeating what several have already written.