Solar panels and battery - any real world reccomendations?

[Oh Ed not again.]

Musing my options for an upgrade. Currently we have 7kw of panels on an east facing roof which are currently maxing out our 5kw inverter.

9kw battery is charged already. And I've got a smart immersion due to be fitted shortly.

I'm in two minds as to where to go next.

1) Upgrade to 8kw inverter to get the "missing" 2kw between 9:30-1 ish. Easy to do, just swap the inverter over.

2) Add 5 400w panels to the front to get a longer peak generation, and help over the winter months. Pain, needs scaffolding/roofer etc.

We are limited to a 3.6kwh export here due to our house being on a spur, so once I've charged/heated all the things I have a fairly restricted export.

 

[Mercenary Keyboard Warrior]

Are you sure you gain any benefit from increasing the inverter?

My logic is, as your export capped the times when you have very high generation your going to hit export cap, full batteries and full hot water very quickly anyway.
Then your back to the same position, what can you do with it.
When generation is low, your not going to be limited by the clipping anyway.
Plus inverters are more efficient at high % so in winter etc a larger inverter would in theory reduce your output. (Probably, you would need to take account of spikes in winter, but probably the odd spike you miss now would be more than offset by a slightly higher % generation for much longer periods)

IMO your number one should be looking to increase the potential to use/store more (cost effectively) before trying to generate more thats quite likely to be unused.

 

[Ron-ski]

I think part of the trick is to always export, to balance predicted solar, battery charge and house consumption to maximise generation, but some systems may not be able to do this.

I'm looking at adding about another 6kW of panels to my Victron system, this would mean about 11 kW of solar hanging off an 8 kW inverter, and once the batteries are full we'd get clipping to 8 kW, but obviously only a summer problem though, but it may not even be much of problem then as 12 panels will be NW, other three SW but vertical.

So if we calculate based on forecasted generation, which on the Victron system seems pretty accurate I can then set the export on the fly, that's the theory anyway.

Luckily my DNO export limit is 11.68kW from the two inverters, so no issues there.

Whether its cost effective is an entirely different question, and a very difficult one to answer.

 

[Journey]

I'm looking at adding about another 6kW of panels to my Victron system, this would mean about 11 kW of solar hanging off an 8 kW inverter, and once the batteries are full we'd get clipping to 8 kW, but obviously only a summer problem though, but it may not even be much of problem then as 12 panels will be NW, other three SE but vertical.

Do it!

Which panels are you going to be getting?

 

[HungryHippos]

I think Ron-Ski needs a rename to reflect his solar addiction!

 

[Ron-ski]

Do it!

Which panels are you going to be getting?

Currently on my short list in order of preference:

• LONGi Solar Hi-MO 5m 410WP Full Black PV Module LR5-54HPB-410M £60
• LONGi Solar Hi-MO 6 430WP Full Black PV Module LR5-54HTB-430M £76
• JA Solar 445W N-Type Bifacial Black JAM54D-40-445-LB-TS-MC4 £84

I think Ron-Ski needs a rename to reflect his solar addiction!

Plan is to get rid of gas, so induction hob and ASHP, so will need more solar

 

[HungryHippos]

Plan is to get rid of gas, so induction hob and ASHP, so will need more solar

I'm jealous I would do the same if I could!

 

[Ron-ski]

Here's what PVGIS estimates for the additional panels. The figures for the existing system are based on the last 12 months totals.

What's interesting is just how much the three panels on the SW wall add in January and December, compared to the NW roof.

 

[tamzzy]

What's interesting is just how much the three panels on the SW wall add in January and December, compared to the NW roof.

how do you wall mount the panels? and how are the electrics connected up to the inverter?
just wondering how to hide and tunnel all the cabling lol
i could probably fit 5 wall mounted panels, hence interested in the logistics

 

[Ron-ski]

I'd probably make my own mounts, but you can also buy wall mounts - just Google solar panel wall mounts.

As for the wiring, that all depends where your panels are in relation to your inverter, my cables (PV Ultra - see previous page) will likely just be surface mounted on the wall and then run across to the garage where my inverter is, I'll then run the various cables through a combiner and then into the solar charge controller.

If you are thinking of connecting to an existing inverter then you'd need a spare PV input on it, and you will need to make sure that the voltages/current from the panels is correct for the inverter input. You may also need an isolator unless its built in to the inverter. There's also the caveat that if adding to an existing installation you may void any warranty if you do it yourself.

 

[b0rn2sk8]

Musing my options for an upgrade. Currently we have 7kw of panels on an east facing roof which are currently maxing out our 5kw inverter.

9kw battery is charged already. And I've got a smart immersion due to be fitted shortly.

I'm in two minds as to where to go next.

1) Upgrade to 8kw inverter to get the "missing" 2kw between 9:30-1 ish. Easy to do, just swap the inverter over.

2) Add 5 400w panels to the front to get a longer peak generation, and help over the winter months. Pain, needs scaffolding/roofer etc.

We are limited to a 3.6kwh export here due to our house being on a spur, so once I've charged/heated all the things I have a fairly restricted export.

Tell the DNO you want an EV charger installing, they’ll probably come and ‘un-loop’ you from your neighbour and then re-apply for your G99. That’s probably as cost effective as swapping the inverter. You can then add more panels to your other roof.

How long are you actually clipping for on that inverter?

I can’t see that you’d get a material benefit from it, particularly when export limited. You’d need to make sure you’ve got a 40a breaker and 6mm feed backs to the inverter, if you don’t, it’s more than just a straight swap.


I’ve got 10kw hanging off an 8kw inverter (9 east 14 west) and I’m only clipping for a matter of minutes at the moment.

 

[reef]

I think part of the trick is to always export, to balance predicted solar, battery charge and house consumption to maximise generation, but some systems may not be able to do this.

I'm looking at adding about another 6kW of panels to my Victron system, this would mean about 11 kW of solar hanging off an 8 kW inverter, and once the batteries are full we'd get clipping to 8 kW, but obviously only a summer problem though, but it may not even be much of problem then as 12 panels will be NW, other three SW but vertical.

So if we calculate based on forecasted generation, which on the Victron system seems pretty accurate I can then set the export on the fly, that's the theory anyway.

Luckily my DNO export limit is 11.68kW from the two inverters, so no issues there.

Whether its cost effective is an entirely different question, and a very difficult one to answer.

When I was looking at getting the second array on the NW roof it was very difficult to find any information on how useful it would be. The general attitude was that it was pointless and generation will be rubbish. There were also no "real-world" numbers on how it would perform. I've only had it fitted since 10th January, but it has outperformed the PVGIS prediction and relative to the SE system in every month so far - about 5-10% better than PVGIS whereas the SE system has been about 5-10% below due to the dull weather. It has also peaked at 3.91kW, so the generation might surprise you from that direction.

I went for an additional 3.68kW inverter for mine rather than trying to get all of the panels onto the existing 5kW one. I pondered one large 8 or 9kW inverter, but the sums didn't add up. Despite being on opposing roofs, it is regularly hitting above 6kW now and has peaked at 7.89kW so far. For me, it also has the advantage that during the peak window on Flux, my 5kW inverter can send out at full whack and any generation from the new 3.68kW inverter goes out too. I've seen export of 7.5-8kW when the sun is shining on the NW array. It also provides a nice evening boost. I discharge to 50-60% between 4pm and 6pm depending on what my use will be that night and then can get 15-20% back before the sun goes down.

It's definitely worth it if you will be using more of what you generate soon. I have a detached garage that could potentially fit another 5.4kW of panels on but I can't make the numbers work as our generation will now be above our annual usage by some way. It would be possible to cover it with export, but I'm hesitant to solely rely on this for payback as tariffs can be pulled and SEG rates can change (and not usually for the better).

 

[Ron-ski]

@reef Yes, there's a lot of outdated information and attitudes out there, I've been following this guy on Youtube, he had a small SE array and larger NW array installed recently.

Its good to hear that your experience also backs this up.

The really dumb thing for me is half the panels on my garage are actually NW, the other half SE, but I always referred to them as west and east, so I know NW panels work well.

 

[200sols]

Personally I think in terms of the main winter months when you really want the extra generation the NW panels just don't generate much at all. I've thought about it, can fit another 13 panels on the NW side of the roof but the financials just don't add up.

 

[Ron-ski]

My calculations show that adding the additional panels will give 54% more generation than my current system for January, and December would be 84% more. Although in the Dec/Jan the much cheaper 3 panel SE wall array will generate more than the 12 panel NW roof array.

If the entire years additional generation was exported at 15p per kWh, then that is £784, a pay back of about 4.5 years, if its consumed then savings will likely be higher and ROI quicker.

 

[Mercenary Keyboard Warrior]

Panels pick up far more reflected solar now I think than they once could
My highest morning numbers are hit when its foggy.
Sounds unbelievable, but they are West facing, so no direct sun. When we have fog (not heavy) its reflecting solar radiation all over the place and hence my array picks up more solar than even a sunny day.

I am still considering an east array. The tree situation out front (I class front as East as thats where my front door faces) even though we are side on to the road which is due south).
Some of the trees have been removed, but we ahev been told people paid for it, even though its a shared area. Anyway, the tress block due NE right round to SE solar for me. But only from April - Oct.
I am fairly sure I would probably pick up at 1kw or so from a 5kw array. In winter I would be pretty happy to double my solar gain, since thats when I end up having to buy expensive units.

Would mean I would need to ditch the wall mounted S array I was considering, but that would be half the size so E facing would probably add more annually, just be not effective in the very depths of winter.

 

[200sols]

My calculations show that adding the additional panels will give 54% more generation than my current system for January, and December would be 84% more. Although in the Dec/Jan the much cheaper 3 panel SE wall array will generate more than the 12 panel NW roof array.

If the entire years additional generation was exported at 15p per kWh, then that is £784, a pay back of about 4.5 years, if its consumed then savings will likely be higher and ROI quicker.

Mine would be NE sorry not NW. Pvgis reckons 5kw of panels would do about 3kwh per year on it.

 

[Seljon]

I had my install completed a few weeks ago. 16 x Aiko 445w panels east/west on a flat roof outbuilding with Sunsynk 8.8kW hybrid inverter and 2 X 5.32kW Sunsynk batteries. A further 8 x Aiko 445w panels on slightly north east house roof with 3.96kW Sunsynk inverter.

Plenty of trees around outbuilding and a couple of chimneys on house roof so went for Tigo optimisers on all panels. The differing outputs of the panels in all weathers really show the benefits of the optimisers.

Very happy so far - only grid electricity used since installation was for charging car (reduced charging speed to 4.4kW) but this was more than offset by export on Octopus Flux the following evening.

Best generation was 30th April as shown below. Bottom row of panels is east facing.

Here is NE house roof

 

[tamzzy]

My first full month on economy 7.
Monthly bill = £19!
Crazy that standing charges is £16 of that £19 :angry:

 

[Ron-ski]

Mine would be NE sorry not NW. Pvgis reckons 5kw of panels would do about 3kwh per year on it.

For here, at 30 degree pitch there is very little between it, exactly NW (Azimuth of 135) 3496 kWh, and exactly NE (-135) 3397.

My NW panels would be at an azimuth of 120 degrees, so a bit better than exactly NW presuming I've managed to work out the azimuth correctly!