When do Micro inverters or Solaredge make sense

tunnel

They originally went for 8kW but got knocked back as the electrics need updating to 3 phase meaning digging up his drive and garden for nearly 50metres to the telegraph pole. They were then told they couldn't go over 3.2kW but appealed and had it increased to the standard 4kW.


Back to the old chestnut now...is the output rated from the inverter cap or the kWp of the panels? The former then they could possibly go more on the panels and cap the output, the latter and they're stuck as is.

Martyn1981

tunnel wrote: »

Back to the old chestnut now...is the output rated from the inverter cap or the kWp of the panels? The former then they could possibly go more on the panels and cap the output, the latter and they're stuck as is.

It'll be the inverter. Presumably the letter(?) is from the DNO. They don't really care what generating kit, pitches, orientations etc you've installed, it's down to what can be exported (and assuming it all gets exported, no on-site consumption).

Can you separate your generation between your systems? If so, ignore the SSW and extrapolate (ok, gut feeling) what kWp you'd have to install across your E/W (ish) panels to hit 4kW, sustained.

My system last week hit a freak 5.3kW, but normally only spikes to 4.9kW, and can't sustain more than 4.2kW, but it can do that for several hours on a really good day in May to July, when the sun's high.

So, for me, 5.6kWp is approx 4kW.

What pitch is your parents house, the steeper it is, the more you can get away with.

Only my gut, but I'd have thought, unless extremely shallow, that 6kWp wouldn't exceed 4kW enough to worry about.

Also remember (and you'll need to confirm this with the installer), that you won't have to install a 4kW inverter, you could go a bit bigger if concerned about the voltage limit, but the installer will have to set it to 4kW when they complete the install. I think SMA's can be 'tuned' in 1W increments.

There's even the option of the diversionary switches that won't allow more than 3.68kW of export. If the water tank/thermal store is maxed out, then they reduce leccy output to agreed cap. I think Immersun are threatening a model that has DNO acceptance to meet kW limits, but I don't think it's out yet.

Mart.

Martyn1981

Just to add, obviously double check everything with the DNO, don't pee em off.

I got clearance for 5.9kW, as all my inverters are slightly over-sized, and the DNO (WPD) approved them as a package. When I rang, with an idea, they confirmed that I can slap as many more panels as I like on the house, without asking them. But I can't install a bigger inverter/combination of inverters, without their approval.

Mart.

tunnel

That's very interesting indeed. Parents house has an east roof at 45 deg and west at 25 deg. Its a shame my dad decided to go against the upgrade but at his age(70+) he just can't be ar*ed with upsetting his nice driveway and lawned gardens, I've tried to persuade him otherwise(house will eventually be mine) but he's having none of it


I put on the renewables about mine hitting 6kW this weekend so what do you think he could get away with Mart?


And which FiT rate would he attract if he had say 6kWp capped at 4? Is that the upto 4 rate or the 4-10 rate?


Decisions decisions...

theboylard

Want to bring your cost down tunnel with a 2 month old Schuco/SMA Sunny Boy 3300?!

Martyn1981

tunnel wrote: »

That's very interesting indeed. Parents house has an east roof at 45 deg and west at 25 deg. Its a shame my dad decided to go against the upgrade but at his age(70+) he just can't be ar*ed with upsetting his nice driveway and lawned gardens, I've tried to persuade him otherwise(house will eventually be mine) but he's having none of it

TBH I don't blame em, nobody likes being messed around. And by the time you get the house, fingers crossed for batteries, DNO approved capping systems etc, so you can slap another 8kWp on. :rotfl:

Too early, and head started to hurt, but I wonder if the differing pitches may help a bit. If you had two south facing rooves, then different pitches would be a benefit, helping to meet kW limits by spreading generation across the year. Not sure if that'll work/matter with E/W but have a thunk. Also, I suspect the West roof will perform quite a bit better than the East on average

tunnel wrote: »

I put on the renewables about mine hitting 6kW this weekend so what do you think he could get away with Mart?

See previous ponderings, I suspect 5kWp will result in little to no capping*. 5.5kWp will give a little, if similar to mine (4.2kW), but not worth a second thought. 6kWp may be more substantial, perhaps trying to hit 4.5kW (? .... not really sure), but again, you've got the experience to know that those losses for a few hours on the best days of the year, don't add up to that much.

* All figures sustained, not 1min spikes.

However, a 6kWp system would/should generate 50% more than a 4kWp system at all times that generation is below the 4kW cap.

tunnel wrote: »

And which FiT rate would he attract if he had say 6kWp capped at 4? Is that the upto 4 rate or the 4-10 rate?

They'd get the 4-10 rate, they may think the 10% drop in FiTs is important, you'll need to explain to them that it's not ..... well, not really, especially if those extra 2kWp only add £1.5k to £1.7k to the price(?)

tunnel wrote: »

Decisions decisions...

Definitely. Please don't rely on my answers. I'm pretty sure on most of it, but you'll need confirmation from the DNO, and an installer who 'gets it'. When I went over 4kWp (and over 3.68kW) with my extension, the first 6 or 7 installers were useless:-

"you can't go over 4kWp" - WHATTTTTT???
"you can't go over 3.68kW" - only if they say no!
"WPD will say no" - well it's definitely a no, if you can't be ar**d to ask em.

and so on.

Since it's you, and I don't need to worry about you taking my comments as fact, rather than opinion, I'll stick my neck out and suggest 5.5kWp (even 6kWp) for me, would be a no-brainer.

Mart.