Solar panels - portrait vs landscape orientation

roadweary

The next thing is the inverter / battery set up.. Most quotes are similar to my preferred Aiko with Sigen design and have a 6kW inverter with a 10kW battery but Gemini says this limits me at 4.6kW throughput in either direction which wouldn't serve me well on a bright sunny summer's day.

Gemini suggests an 8kW inverter wtih two 8kW batteries. Does that make sense or does it sound like overkill.

I have another quote with Tesla and Eurener panels, but I prefer the sound of Sigen at the moment and how it deals with the panel output in different light / shading conditions.

thevilla

North facing panel with zero tilt are the same as south facing panels with zero tilt.

Our 20 degree north facing panels generate 70% of the south ones over a year. The tilt is important.

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/82020553#Comment_82020553

Agreed. North facing panels at a 40 degree tilt will generate ~40% of the output from a South facing panel with the same tilt. From an ethical and economic perspective, not worth it in my view. Instead, I'd invest the funds in a heat pump, an expansion pack or a cheap EV.

https://www.sunsave.energy/solar-panels-advice/installation/angle-and-direction

Martyn1981

https://forums.moneysavingexpert.com/discussion/comment/82024321#Comment_82024321

That sounds a bit harsh, did you mean a 50d roof?

For my location in Cardiff I see approx 40% for a 50d roof, 50% for 40d roof and 60% for 30d roof (which is actually my roof pitch).I'm using PVGIS.

I have E/W roofs, which work out at about 85% of south facing, so two roofs approx 170% of south, but if N/S that would be 160%, which still seems fine, especially as the cost of twice the kWp won't double the install bill. There will be savings on scaffolding, and the AC side work, and probably on the total bill for doing 'two jobs' so less paperwork and admin (proportionately).

QrizB

^ I've just done some quick PVGIS runs.

In the south of England (Southampton Eastleigh airport):

• 40 slope, 0 azimuth: 1058 kWh/kWp/yr
• 40 slope, 180 azimuth: 517 kWh/kWp/yr

In the midlands (East Midlands airport):

• 40 slope, 0 azimuth: 1000 kWh/kWp/yr
• 40 slope, 180 azimuth: 492 kWh/kWp/yr

In the north (Newcastle International airport):

• 40 slope, 0 azimuth: 956 kWh/kWp/yr
• 40 slope, 180 azimuth: 454 kWh/kWp/yr

That's 49%, 49% and 47% respectively.

Screwdriva

Hard to be precise (hence the ~) but it's definitely < 50%. Less so for bifacial panels but I still wouldn't recommend North facing. My apologies if that comes across as harsher than intended - just trying to optimize for satisfaction/ return/ ethics. Ultimately, to each their own.

Newbie_John

@Screwdriva , it really needs a bigger picture.

South is great for general volume output but most of it is around 13:00 - so you need to have battery to collect it or rely on good export rates lasting for many years - and let's be honest, they will go down in time.

North provides more in early hours and in the evening - when you're at home - so they're great for own consumption, they really support the south facing extending "free" electricity window.

This website says they should still generate 50% of south output :

https://thesolarco.uk/blog/north-facing-vs-south-facing-panels-is-north-worth-it/

So I guess if you don't get battery, not at home during working hours and the cost of adding them as extra isn't too high (panels are cheap now, labour is expensive) then they have a really good case.

roadweary

I'm negotiating prices and payment milestones at the moment with a couple of providers. My main concern is the DNO allowance….I'm going PW3, but would be a kick in the teeth if they didn't allow me more than 7k

roadweary

Btw, the North facing panels get weird and wonderful shadows in all shapes / orientations from the ever growing trees over the road. I think most modern panels are effectives split into six rectangles…..but Aiko supposedly would deal better again….

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/82033575#Comment_82033575

You're right, it does need a bigger picture. I typically ask myself 3 questions:

1. Can those panels on the North aspect be more efficiently used on another roof's South/ East/ West aspects where the same panel could generate more than twice the power?

2. To your point on efficiency of spend, can the £ spent on North facing panels be used more efficiently elsewhere towards more effective measures to improve the household's green credentials ? (loft insulation? home storage? triple glazing? a cheap EV?

3. What will the panels generate during the 7 months of the year when North facing panels suffer disproportionately from a lower sun?

Just a couple of counter points:

A) While South facing panels do peak in generation around mid day, they begin generating from as early at 6am. Here's a curve from a South facing system taken last week.

B) While standard Solar export tariffs may reduce in the future ( I am still paid 16p per kWh and I don't own a battery), I don't see smart export tariffs reducing. Quite the opposite, as the need for the grid to pull from connected home storage appears poised to increase.