Solar panels - which orientation?

Beanbag_35

Hi

My first ever post here.  First of all thank you to all the very knowledgeable people who share their expertise here - I have learnt such a huge amount from previous posts and become more confident in choosing between quotes.  I'm going for 15 x Eurener panels, Solar Edge inverter and Solar Edge battery.  However, I have two differing views on where to put the panels and I'd appreciate any insight anyone has on which to choose.

My roof is East / West facing and the panels will be at 45' tilt.  There is a big mis-match in assumed generation in two different quotes, both of which are 7.5kWp systems.  The first suggests all 15 panels on the west facing roof and estimates solar generation of 7,068kWh.  The second suggests 7 east facing and 8 west facing panels and estimates solar generation 5,482kWh.  That's a huge difference.

I can believe that lower second quote estimate as although you theoretically have sun all day, you only have half the panels on each side.  The first estimate seems an optimistic view of efficiency.

What do people think?  Do you think it would be best to split East and West or should we go all West?  Would there really be that much difference, or is the first quote just too optimistic?

Look forward to hearing any views.

born_again

Having it split across both east & west would be best, given sun rises in east & sets in the west, so you get more actual coverage of the sun. 

Screwdriva

Welcome to the the GEMS sub-forum! It's a generally helpful and very knowledgeable place - I consider myself very fortunate to have learnt so much from my fellow members! 

Hope you won't mind a few thoughts/ questions:

1) Any reason why you're investing in the SolarEdge battery vs. a Tesla Powerwall 3 battery inverter, which is generally accepted to be a far more capable/ future proof solution, while actually costing less? 

2) DNO permission allowing, I would fill both aspects with as many panels as will fit (atleast 23 from the sounds of it). The PW3 has 3 string inputs so can easily handle both aspects. Solaredge has optimizers, which allow multiple aspects as well. 

3) If you are restricted to 15 panels for some reason, splitting them across both aspects will perform better across the seasons, assuming a pure E/W aspect. 

4) What is the Wattage of the Eurener panels you have been quoted and are they bifacial? 

5) Would be good to know what you have been quoted for the SolarEdge system to see if we can help save you some £ too! 

Regardless, best of luck with the PV journey!

badmemory

I would agree with as many as you can on both sides.  I have found my west ones are bad in winter but great in summer & my east ones are better in winter & not quite so good in summer.  Whilst I have had them for nearly a year they have only been running properly for a few months (smart meter issues) I have enjoyed having a minus bill for May & June & looking forward to one for July.

QrizB

My roof is East / West facing and the panels will be at 45' tilt.  ... The first suggests all 15 panels on the west facing roof and estimates solar generation of 7,068kWh.
... The first estimate seems an optimistic view of efficiency.
What do people think?  

I think that when they modelled your "all west" option they forgot to set the azimuth to west. 7068 looks more like a south-facing model.

I've done a very quick model in PVGIS:

https://re.jrc.ec.europa.eu/pvg_tools/en/

For a system in central Birmingham, 7.5kWp facing south at 45 degrees of tilt is forecast to generate 7261kWh a year. Facing west it's 5461kWh.

The same system split east-west generates  2809 (east) and 2731 (west) total 5540kWh per year.

Edit to add: that's an equal split, so 7.5 panels on each roof which isn't quite realistic but you can see that both aspects are similarly productive (east slightly more than west) so it's not going to be significant.

Screwdriva

QrizB said:

The same system split east-west generates  2809 (east) and 2731 (west) total 5540kWh per year.

I would only add that the generation curve would look very different for a West vs. E/W aspect installation, with the latter being more evenly spread through the day. 

Beanbag_35

Wow - thank you all so much for your fantastic feedback and advice. 

Hearing your "real world" experience is really valuable, badmemory  

Screwdriva - to respond to your questions:

1) I would have gone for Powerwall but my husband feels very strongly that he doesn't want to support any company owned by Musk.  I'm willing to support his stance here as I think (hope) that SolarEdge is still a good alternative.

2) Thank you, and echoed by others - I'm running the calculations for adding more panels and I know they will tell me you're right and we should go for more.  I am concerned about DNO outcome, though - and I don't know how to get any view on what their reaction might be - make the application and wait I think.

3) Agreed - and all of you here have shown me that East/West split is the way to go.

4) The panels are 500w Eurener Nexa Bi-Facial Panels panels - so hopefully they are a good option? 

5) I suspect you already have saved us money - I saw Light Renewables recommended in a few posts on here and they have quoted £11,695 which was much more competitive than the local suppliers who quoted (and better panels, too)

QrizB - wow - you are amazing.  I saw the PVGIS model and planned to put a cold towel over my head at the weekend to work out how to use it - and you've done it for me.  Thank you so much for taking the time to do that, I really appreciate it.  I think you're right, our other quote didn't adapt for West facing and you have given me comfort that the LR estimate for the East / West split looks sensible.  We are in the Midlands, so great pick of Birmingham.  Fantastic to see the figures for both all west or split east/west as well - not a huge difference, but as many of you have pointed out it gives a more even spread during the day.

So - East/West it is plus a request for panels.

I'm so pleased that I posted 

QrizB

I can understand your preference for a SolarEdge system.

Glad we've all been able to help, do keep us informed of progress with your installation! And if you need anything else, just add your questions to this thread.

charles_b_2

Beanbag_35 said:

1) I would have gone for Powerwall but my husband feels very strongly that he doesn't want to support any company owned by Musk.  I'm willing to support his stance here as I think (hope) that SolarEdge is still a good alternative.

Solaredge is a good system, I've had mine (15 panels x 450w, SSE orientation) for a year and it just works. 
You can also have 3 batterys connected daisy chained together.  I started with 10kWh and am looking to add an additional one to assist with the low output during winter.

I wonder with the split what the peak output would be, as that will have a bearing on the choice of Inverter, you might be OK with the 3.6kW.  Bear in mind that the Solaredge battery is DC connected, so anything above 3.6kW will charge the battery, but you will be limited to 3.6kW output to the house or grid.  I went with the 5kW inverter, as I had a single aspect roof with almost optimal orientation.  Note that adds cost (and possibly time depending on your DNO, took 3 months for SSEN)  as you have to apply for G.99 rather than the automatically allowed G.98 application with the inverter.

Screwdriva

Beanbag_35 said:

Screwdriva - to respond to your questions:

1) I would have gone for Powerwall but my husband feels very strongly that he doesn't want to support any company owned by Musk.  I'm willing to support his stance here as I think (hope) that SolarEdge is still a good alternative.

2) Thank you, and echoed by others - I'm running the calculations for adding more panels and I know they will tell me you're right and we should go for more.  I am concerned about DNO outcome, though - and I don't know how to get any view on what their reaction might be - make the application and wait I think.

3) Agreed - and all of you here have shown me that East/West split is the way to go.

4) The panels are 500w Eurener Nexa Bi-Facial Panels panels - so hopefully they are a good option? 

5) I suspect you already have saved us money - I saw Light Renewables recommended in a few posts on here and they have quoted £11,695 which was much more competitive than the local suppliers who quoted (and better panels, too)

1) I have previously recommended SolarEdge as an excellent option but I have to be honest and share that the battery inverter system has been outclassed by the Tesla PW3. Charge/ Discharge/ Peak Generation or Export are significantly superior (assuming DNO approval is received) and the battery chemistry is considered safer than SolarEdge. There are several other benefits such as software, cold weather performance (a big one), lower cost etc. I understand the Musk sentiment but the SolarEdge storage solution is now considered a different tier when compared to the PW3, with very few exceptions, such as heavy shading or 4+ roof aspects. 

2) Your calculations will show that more panels = faster return on investment to a degree. I would suggest maxing out the panel coverage now and if the DNO approval comes back lower than expected, any honest installer will re-size the system to accommodate this. Remember E/W orientations need slightly more generative capability relative to peak inverter size. e.g. 10kW of panels for an 8kW rated inverter. 

It will continue to get harder to secure higher (>10kWh) export allowances as the grid becomes more saturated - it would be wise to aim for the moon and land wherever you do. 

4) Superb panels - currently my top pick.

5) Thanks - I use 4 installers across England and Wales. LR have been asked to look after MSE forum members - 10 year workmanship warranty, bird netting, white background painting (to maximize bifacial gains) and top tier brands all included. If they haven't included any, feel free to DM me and I'll ask them to include these and look after you. 

jackieblack

Hi, sorry to jump in but is this Light Renewables in Maidstone?

(I will hopefully be moving in a couple of months and plan to put a PV system on the new place - batteries weren’t a thing when I got panels on my current home and things have moved on ALOT in the last 15 years!)