Renewables: "talking 'bout my generation"

Martyn1981

InVestor wrote: »

10.4 bananas today.

Yes, 4kWp, south facing, not sure angle looks about 45deg. Does work well in winter (Well, not so much this year)

Good guess!

Actually I was just horsing around, so a lucky guess.

1.6'O's for me (9kWh's)

Mart.

PS Regarding kWp of panels or inverters, my vote goes for panels, with 5.9kW of inverters I'll have "too low O's, or a no show, each go". M.

John_Pierpoint

Yes my panels are slightly "bigger" than my inverter.

We could have a competition about who get the highest yield per sq meter of roof:D

The Mark group would accuse me of "roof cramming".

jackieblack

John_Pierpoint wrote: »

Yes my panels are slightly "bigger" than my inverter.

Mine too.
Fronius IG20 (I believe) has max output 2kWp, panels = 2.22kWp (12 x 185w)

So yesterday, 6kWh generated, would = 3kWh/kWp if using the inverter figure, 2.7 if using panels

KevinG

EricMears wrote: »

Suspect you'll find it's either the kWp of panels or kWp of inverter - whichever is the lower.
(So much easier when both are same )

Not sure I agree with that. I think that a 4kWp panel system with an inverter limited to (say) 3.68kW should be treated as 4kWp otherwise you will get an artificially high 'O' figure most of the time. I treat my system as 2kWp even though the maximum possible output of the inverter is about 1.7kW (despite being sold as a 2kW inverter).

EricMears

KevinG wrote: »

Not sure I agree with that. I think that a 4kWp panel system with an inverter limited to (say) 3.68kW should be treated as 4kWp otherwise you will get an artificially high 'O' figure most of the time.

But I believe that is the definition that determines which FIT group your installation would qualify for.

Since the 'O' isn't an official unit, I guess you could define it any way you like but it loses all credibility if different people define it differently.

InVestor_2

EricMears wrote: »

But I believe that is the definition that determines which FIT group your installation would qualify for.

Since the 'O' isn't an official unit, I guess you could define it any way you like but it loses all credibility if different people define it differently.

Isn't the FiT decided by size of panels only?

Martyn1981

InVestor wrote: »

Isn't the FiT decided by size of panels only?

Yep. But, the wording suggests inverter size, efficiency and capping should be relevant, as it talks about the maximum power that the system can run at for a long time (ignoring short bursts from cold panels).

However, reading other forums, and the electricians forum, OFGEM (and the FITs providers) are sticking with the kWp of the panels, not the output of the inverter). The next step for the solar industry would have been to challenge OFGEM's interpretation in court, and that would have cost a few £10's of thousands, so hasn't gone any further.

[Edit: doubt any challenges will be made now, since the 4-10kWp rate is only 10% lower and leccy savings and export rates aren't affected, so 'lost' income from going over 4kWp will be marginal, and could even be worth it as panel prices have fallen, so going bigger can drag down the cost per kWp installed.]

Personally, and unscientifically, I reckon if you want to measure how much rain has landed in a bucket, you compare it to the total size of the bucket, not the size of the funnel used to move it, especially if the funnel is inefficient, undersized, or capped.

Mart.

The_Green_Hornet

I believe that you should use the figure specified on your MCS Certificate which in my case is the panels and not the inverter.

InVestor_2

The_Green_Hornet wrote: »

I believe that you should use the figure specified on your MCS Certificate which in my case is the panels and not the inverter.

I thought most (all?) inverters in the UK were slightly under the panel size for most efficiency?

I read somewhere about too small and it would explode or something, not sure I believe that though.

Anyway, getting off topic.

EricMears

As I said before, so much easier when both are the same

However, I'm sure the word "nett" appeared somewhere in the official definition (although I can't find that today and it really isn't worth the effort of looking).

I'd certainly go along with using whatever your MCS certificate says.

In my case that is of course 4.00kWp - since both inverter and panels are officially rated at that. However, I ought to have a good chance of exceeding that sometimes (not that I ever remember doing so) since the panels are declared to have 'positive tolerance' and the inverter is supposed to have capacity to exceed spec for short periods.