Is it worth getting 2 extra solar panels?

Martyn1981

ispookie666 said:

Leaving all this aside, what is your current export limit? Will the installer go back to DNO for further notification ?

Only my assumption, but given the cost of the upgrade, it looks like there is no change to the inverter, so there should be no issue for the DNO. The DNO will already have approved the inverter, or if necessary, the capped limit on the inverter.

Edit - Just a thought, but there may be an exception, but I don't know if it's likely. DNO's could (not sure if this is still the case) give the simple approval to systems that had 3.68kWp or less of panels, even if the inverter was larger. In such a case, the addition of panels might potentially mean crossing over the 3.68kW line, but that's probably unlikely, especially these days, with more powerful panels, so larger kWp installs, and the tendency to undersize the inverter a bit, for efficiency.

Screwdriva

Martyn1981 said:

Only my assumption, but given the cost of the upgrade, it looks like there is no change to the inverter, so there should be no issue for the DNO. The DNO will already have approved the inverter, or if necessary, the capped limit on the inverter.

My understanding is OP's inverter will remain as is. Given the dual aspect nature of the install, clipping is very unlikely.

Indeed, I've found that adding a 2-3 panels to an existing multiple aspect installation brings performance closer to the theoretical maximum generation an inverter could allow, with very little clipping if at all, while providing a useful boost in performance for 9 months of the year. 

In my own case, I've retained the 3.68kW inverter (for now) but added >80% more bifacial panel coverage (3.3kW) to my WSW and East aspects, while keeping the SSE panels as is. I expect to clip for a couple hours midday in the summer, but can't justify the upsizing of the inverter for the full year (yet). 

The biggest challenge has been finding panels that match the existing set aesthetically and dimensionally. 

pete-20-11

My 8 panels look very nice, possibly could have got a 9th on with a small amount of clipping, but it would have been 5 on one row and 4 on the other. What price for uniformity!!! 

10 would have been ideal, fill the roof, but then there would have been serious clipping in the summer with the size of inverter. 

Advice is to always get more than you want, subject to some clipping if need be and inverter size. 

QrizB

ispookie666 said:

Leaving all this aside, what is your current export limit? Will the installer go back to DNO for further notification ?

Per the OP's previous thread, they already have 18 panels. Adding two more (10%) is unlikely to require any other changes.

They might clip a little bit more in high summer, but that's all.

powerful_Rogue

Screwdriva said:

We were able to get the cost of the 410W panels reduced a bit further. I think OP will be pleased with the extra generation. 

That said, the incremental cost for a panel during the first installation ranges from £250-300 (with optimizer). No system expansion cost can ever be that low, given the fixed costs involved, so it always makes sense to maximize South/ West roof aspect panel coverage during the initial quote. 

Very good advice.

Wasn't until all my panels were fitted, the installers said I could probably fit another 3 on the front and 3 on the back.

Will get a quote at some point to see how much it would cost and whether it would be worth it.

Screwdriva

Cheers!

Six panels would cost ~ £2K. With a 2.5kW increase, I’d suggest a larger inverter unless you’re significantly under-generating in the summer months.

powerful_Rogue

Screwdriva said:

Cheers!

Six panels would cost ~ £2K. With a 2.5kW increase, I’d suggest a larger inverter unless you’re significantly under-generating in the summer months.

Would you say the above would need changing if I looked at getting extra panels?

Solar Edge  SE6000 HD Wave inverter

Growatt SPA3000w

Screwdriva

On further reflection, I do not believe any other upgrades for your existing system are necessary.

My guess is that your existing system has rarely eclipsed a peak generation of 4.5kWh during the June-August months last year, with a nice flat'ish plateau of ~4kWh peak on a clear midday . Would be great if you could confirm this?

This means that you have quite a bit of room for additional generation from 3 panels on each aspect before your 6kW inverter will clip. I would not recommend any other additions other than augmenting your existing system with the 6 X 410W panels. This should speed up your overall system's return quite a bit  

That said, I am loving my newly added SolarEdge modbus. Be warned, staring at the live generation/ import/ export/ household consumption data is addictive! 

cloudstar

I have a similar scenario at the moment. We had 11 panels 4.4kwp installed April 2023. Our house was built in 2015 and already had 2 x 250w solar panels with micro inverters installed. The installer at the time said they could remove and replace the old panels FOC (I think) but I decided not to have them removed.

At installation time they said they could fit up to 4 extra panels if the old ones were removed on the south facing roof. Our roof is complicated and has 4 gables. We have 4 x 400w panels on the east and west facing roofs and 3 x 400w panels with the 2 x 250w panels on the south facing roof. It may also be possible to add an extra panel on the east and west facing gables making a potential total of 6 extra panels.

The 2 x 250w panels generate around 500 to 600kWh per year on average. So far since April 2023 the 4.4kwp system has generated 3.52MWh. The inverter is 3.68kw and we haven't had any clipping in the summer with peaks around 2.9 - 3.2kw on a hot sunny day 

We have an EV and not batteries installed at the moment.

Any thoughts on adding additonal panels?