Extending PV Array

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E3xtc

773 posts

Ultimate Geek

#318564 30-Jan-2025 10:51

Hello,

We have an existing PV installation which has 4kw of panels on a 5kw inverter. I am keen to extend this to ensure we are getting the most out of the system, so thinking about throwing another 1-2kw of panels on the roof. What are peoples thoughts on whether adding 2kw of panels makes sense over adding just 1kw - ie whether the panel output should equal or be greater than the inverter?

Also keen to get people's recommendations on installers for this - we are in (west) Auckland fwiw.

Thanks in advance for your thoughts.

billgates

4705 posts

Uber Geek

Trusted

#3337327 30-Jan-2025 11:30

Panels output should be greater than size of inverter by atleast 1.25x. This is to allow to compensate for panel performance degradation over time and also provide more solar output on overcast, winter or rainy days. If you have a 5kW inverter, you should have at least 6.3kW of panels

Do whatever you want to do man.

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#3337348 30-Jan-2025 12:07

Note that many inverters have a limit of how much PV you can connect to them, so you likely want to be right on that limit.

SteveXNZ

59 posts

Master Geek

Lifetime subscriber

#3337391 30-Jan-2025 13:39

Have a close look at your inverter spec. What's the maximum PV input? How many MPPT strings? What orientation are your current panels?

With a single MPPT you could add panels in the same orientation up to the limit of the inverter. With two MPPTs you'd have the flexibility to add a second set of panels in a different orientation, eg to increase generation in the morning or evening peaks.

I've split my panels over a NE and NW orientation to provide more uniform PV over the day rather than a big midday peak that may be difficult to self-consume.

As a general rule, configure as much PV as your inverter will allow. The incremental cost of additional panels is small compared with the benefit gained. This will cover you for dull winter days, while summer excess can be exported for a credit.

E3xtc

773 posts

Ultimate Geek

#3337589 31-Jan-2025 08:29

Thanks everyone for the input. Yeah we should be able to extend the number of panels (model number SB 5000TL-20) as it has multiple MPP strings and the input rating is more than what we currently have on the roof. Am sending out some feelers to see what the industry comes back with.

I believe we currently have a single North facing block albeit split into 2 at the moment with half the array to better cater for afternoon/morning shading that happens...but that certainly could be rejigged/optimised if we get more put on a different part of the roof to optimise that for afternoon.

Will see what comes of this exercise. Thanks again

E3xtc

773 posts

Ultimate Geek

#3340100 7-Feb-2025 11:23

So it looks like we have a bit of a challenge with extending our array.

Our max input is 5300 (very low for a 5000w inverter evidently; likely due to its age). Our existing array is rated at 4000w, so that leaves only space for 1300w of panels - which at the current size of panels is about 3 or so panels. So we can't overclock/install more panels than the inverter is rated for so the gains are going to be pretty minimal for the cost. It looks like it would still cost 5k-ish to get a handful of panels on to the roof to extend things.

Whereas we could look at getting a new 10kw inverter and just fill up the roof with new PV panels, and have the old panels going into the new inverter along with the new panels - giving something like 13kw of (theoretical) output, all for about 11k. Seems a better cost/output ratio.

Biggest downside is that all the new panels would have to go on the south facing roof - although I have been informed the loss is only about 10%.

Still not thinking about a battery, but wondering if I should ensure the new inverter at least has the plugin ability to allow it to be added later? Hmm

I wonder whether I can recoup any money from the sale of the old Schuco 5000TL-20 inverter too :\

As always, it looks like this is going to be one of those projects that grows to be more (money) consuming than expected. Ugh