8kWp PV panels into a 6 kW interter an analyis

ECO_Mental

Currently, I have a 6.1 kWp PV system (18 JASolar 340W panels). I'm messing about thinking about expanding to 8 kWp by replacing my existing panels (or add, but my roof space is full up practically) to my existing 6 kW Solis inverter, as I believe this is the maximum input capacity. I think this would be the simplest and most cost-effective way to upgrade.

To evaluate this, I used Grafana to analyze a year's worth of PV generation data in 15-minute intervals. I multiplied each interval by 133% to simulate an 8 kWp system. Then, I capped any output exceeding the inverter's 6kW limit (1.5kW/15-mins).

My analysis shows a potential max increase in daily production from 44 kWh to 54 kWh (a 21% increase) on ideal days like May 30th, 2023. Over a year, this translates to approximately 1,900 kWh more, a 30% production boost with a 33% increase in installed capacity.

The percentage gain would be even higher during winter months I would get the full 33% increase in production, potentially allowing me to utilize a larger portion of the generated energy.

Worst-case scenario, exporting the additional 1900 kWh at a €0.20 FIT rate would yield €380. However, I'd likely use a significant amount of this power during peak hours when rates are higher (€0.30 - €0.40), increasing the financial benefit.

Although my two existing strings are uneven (12 and 8 panels) and I'd need 450W panels, and I'm unsure if they'll integrate seamlessly with my current setup. This is probably a medium-term project, as the cost is a factor at the moment. This info could be useful to others here.

My long-term plan may involve a substantial ground-mounted system (I have the space), but that is long term…

Does my rationale and calculations seem accurate?

oaklands

Some hybrid inverters will take more energy from PV and provide more than the rating to battery+grid. Output to grid will be capped and if no battery or if full will limit energy from PV.

So you should verify this in case your current inverter may already support 8kWp panels.

see snippet from one Solis 6kW datasheet below, which suggests it will take 8kW from PV and limit grid to 6kW.

bullit_dodger

That's an interesting way in doing it ECO. I wouldn't have thought of that.
When you were normalizing the data, I assume you took the hour change into effect from your historic data? (Summer/Winter time)?

Your analysis is inline with my own thinking. Dropping an extra 2Kwp there, and not upgrading your inverter from 6kwp, will involve some clipping, but really that loss is only 3% off the theoretical additional yield. People assuming "ohh I have clipping, must get new bigger inverter to solve that", but in reality, you would only get a small additional fraction.

For many months, like Jan or Feb for example, there is limited clipping going on.

johndoe11

I have 8.4kwp connected to my Solis 6kw, although it is east west. 21 400w panels. The installer said 22 panels was the max it could take, 11 on each string.

graememk

The voltage of the panels is what determine how many panels you can fit.

I have 24 on a 6kW, but they are 360w panels.

It's the voc you need to worry about.

But if you are limited to 18 panels, 2 string of 9 is no issue unless the voc is really high