Solar advice please (quote and options)

Screwdriva

As shared previously, I would skip the NW roof entirely. North facing panels experience a 50% production reduction when at a negative 20-degree incline. The production reduction is even greater with inclines > 20 degrees which you clearly have.

How many panels were included in the quote/ what was the size of inverter? 

Martyn1981

Rahulpdev said:

I can see now that my previous comment was very unclear, apologies all!

Based on PVGIS calcs (and how they represent azimuth) the SE roof is -35°, the NW roof is 145° and 61% output of SE, and the SW garage roof is 55° and 94% output of SE. 

First quote has came in from Boxt for JA Solar panels and Sunsynk inverter. £8k for SE roof plus garage, £11k i.e. 37.5% premium to add the NW roof.

(Yes, roof pitch is 35°)

Thanks, so based on an azimuth of +145d for the NW roof, I don't think I'd go for it. Worth seeing how much more it is, in case the 'smaller' additional cost makes up for the poor performance, but also important to know that most of that extra gen will be during the summer, when you'll have lots all ready.

LateStarter

Hi, it's interesting to hear you talk about the NW roof, as I've got a similar dilemma. Had 5.5 kW installed on the other side in March, it so far it seem pretty good - about 600 kWH in April. But we're away most of the day, and production drops off drastically after about 5pm, even though I can see the lovely sunshine on the NW roof on evenings. I'm still wondering if I should have put some panels on the NW side, or if to move some of my existing ones there.

Martyn1981

LateStarter said:

Hi, it's interesting to hear you talk about the NW roof, as I've got a similar dilemma. Had 5.5 kW installed on the other side in March, it so far it seem pretty good - about 600 kWH in April. But we're away most of the day, and production drops off drastically after about 5pm, even though I can see the lovely sunshine on the NW roof on evenings. I'm still wondering if I should have put some panels on the NW side, or if to move some of my existing ones there.

I wouldn't consider moving panels from the SE(?) roof. You might want to consider an additional NW system, but ideally you'd want to share the same inverter, to keep costs down.

Only my opinion, but for roofs that are to the north side, rather than south, you really want to do tem at the same time as the southerly roof, to reduce the cost of the northerly roof, as mentioned earlier.

I'm a bad example, as I added the WNW roof separately and later, but this was during FiT's back in 2012. So the subsidy makes up for a lot of the extra cost, and poor performance, and I should breakeven around summer 2025 (not including leccy savings, so probably there already).

As per earlier posts, the orientation is really important, so WNW might be poor, but viable, whereas NNW will be much harder, so PVGIS is your friend. But note the drop off in winter, not just the annual reduction. My WNW is great May to August, but most of that extra is exported.

Batts will help, both for off-south roofs, but also to shift your SE generation to the evening, which may be more cost effective soon, as storage costs keep falling.

[I suspect my answer has simply created more questions, and answered little.  ]