Adding new panels to existing system

Hi, we had a 3k system in stalled 7yrs ago which never delivered the bill reduction we were hoping for (we do have a pool pump and largish house). Any advise always leads to my being recommended a new 6.6k system as n if previous doesn’t exist, is there an effective way to incorporate the investment we have already made?

Hi @catherinemorwood1

I’m not sure how you would incorporate the old system? How do you mean? Do you mean so that you have 6kW total, rather than 6kW plus 3kW?

You could certainly get a smaller new system.

This quote you have posted does not show the products they are selling, that’s quite strange. Have they listed that elsewhere?


So I would need a little more information, however, we have just completed two system expansions and upgrades using clients existing panels and racking. We changed out their current inverter for Enphase micro-inverters. On one system we added 6 more panels the original panels were 340watt and we added 385watt panels (no need to size match with Enphase) took a couple days and the new system was up and fully running. The only real loss for the client from the old system was the string inverter (which would have needed to be changed out for a larger model anyway).

The second system we added 4 - 385 watt panels and removed 6-255 watt panels from the existing string inverter. These 10 panels are now connected to Enphase micro-inverters and monitored on a separate monitor. The 6 existing panels are 255watt 60 cell panels connected with IQ7 micro-inverters and on the same line are the new 385watt 72 cell panels connected to IQ7+ micro-inverters. As well the client did not have the money to do a full system change over at this time so we left 7 255watt 60 cell panels on their existing Kaco string inverter. As they can, they will have us back to continue to move panels onto the micro-system, but for now they have two systems in operation. This was a very economical solution for both clients, who did not want to see the original system go to waste.

Hope this helps.

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Hi Catherine

Where is your place?

I have a largish house with a pool. I installed a 10kW system and have received credits averaging $250 per quarter. My average usage per day is 20kWh in Summer for one quarter it went upto 34kWh but normally around 17kWh.

Do you know how much you are using.

I can work out a rough estimate of your savings should yopu want me to.

Is the quote from a CEC approved retailer?


If I may, I have a similar query. Is it possible or even worthwhile at all, to add extra panels to our existing system. It was installed just eight months ago. The system size is 5.31 kW, has 18 × 295W REC TwinPeak panels and a Fronius 5kW Primo inverter. Is that inverter able to take extra panels, or is it already maxed out? Thanks

Hi @mudlu

No, there shouldn’t be a technical issue with going up to 6.6kW (can’t go over that).

I’m assuming there isn’t space restrictions or anything? If you want to do it, better to do it sooner rather than later I reckon.


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one of the limitations we found when similarly looking to expand an existing 7yr old system was that the Inverter we currently have does not have capacity to add extra panels. We did find lots of people though willing to simply add a new 3 KW system on our roof (so we will have 2 inverters and two seperate strings of solar panels. We have gone with that because we only replaced our Inverter a year ago. If your inverter and panels are both 7 yrs old then the Tech advances our conclusion is that we would be better off going with a new system entirely and get much better and longer lasting return on investment
Hope that helps - from another consumer with no other qualifications related to energy

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Thanks Marty, Yep , we’ve got no concerns with space, as have got heaps of room to place them.


Marty, one last question, how many more of the above panels could we fit to max out near that 6.6kW figure. Thanks


So it’s 6600W - 5310W = 1290W. Then 1290/295W = 4 more panels.


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Thanks Marty, I didn’t realise it was that simple.


Fortunately some things are :slightly_smiling_face: