Talking about solar PV, inverters, efficiency and performance

mrmmhf

There's a lot of confusion (on my part anyway) about the size of inverters and the role they play in solar PV installations. We hijacked a different solar PV thread, and are moving it here to continue discussing the technicalities of solar PV installations. This is the last response:

“One last thing* another reason for undersizing inverters relates to the permission required from the DNO when you add a SSEG (small scale electricity generator) to the network. For anything that can (even theoretically) export 3.68kW's or more, you need prior approval from them.

So, combine this with at the time a FiT tariff that reduced at 4kWp+, and we get an additional reason to keep the inverter at or below 3.68kW. Basically as far as the DNO was interested, you could have as much PV as you like, so long as the inverter wasn't capable of exceeding an AC output of more than 3.68kW.

When I added to my original 3.58kW system that at the time had two inverters totalling 3.7kW (in this instance the PV being under 3.68kW) I had to get permission from the DNO, and I'm now allowed to have inverters totalling 5.9kW.

*Obviously I and others love to chat about PV and all the ins and outs, but to prevent too much diversion on this thread, best to choose another, or might I suggest you start one based on your personal set up, as I find it interesting, and my sister has just bought a property with mains leccy and water but no other services, and when she moves in I'm on call to offer suggestions such as heatpumps, PV etc etc.. So the more you can share the better.
Originally posted by Martyn1981
”
I have just watched the video which I thought was excellent. I noticed in the video that the installers initially supplied a 5Kw inverter then replaced it with a 6kw inverter. I think it might be worthwhile the OP checking with the installers that they got DNO permission for 6 Kw. I had a system installed last year and when I decided I wanted to add some panels I asked my installer what capacity system had been approved by my DNO. It turned out the DNO application had not gone through even though I had 7.2Kw inverter capacity. Negotiations are ongoing with the DNO but it hasn’t started off well with the DNO only approving 5.9 Kw capacity (which coincidentally is the same as what Mart was offered).

Apologies for continuing to take this thread off topic but maybe when the OP posts his next video update (which I am looking forward to) it could be done under a separate Home Farm Solar Installation thread.

Ken

mrmmhf

Thanks for the feedback Ken, and thrilled you liked the video.

We used EON for our installation, and they were painfully meticulous, so I would imagine that the we have the correct DNO approvals. I will, however, contact them tomorrow to make doubly sure. I will also check the DNO approval myself later tonight because that was sent to me.

Looking forward to more of my solar PV questions being answered here.

1961Nick

mrmmhf wrote: »

Thanks for the feedback Ken, and thrilled you liked the video.

We used EON for our installation, and they were painfully meticulous, so I would imagine that the we have the correct DNO approvals. I will, however, contact them tomorrow to make doubly sure. I will also check the DNO approval myself later tonight because that was sent to me.

Looking forward to more of my solar PV questions being answered here.

Maybe ignorance is bliss....;)