Is it worth me spending 5k on Solar Panels?

tumptyteapot

Exiled_Tyke wrote: »

Go to http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php and check out the estimated output for the size of system and where you live. (don't worry about the technical options on there, they don't make too much difference).

As always, get a few quotes and then come back here and ask for more opinions. People here are always very willing to help and would rather you pestered them with questions rather than make a bad decision.

From what you have described so far it sounds like you need a system with optimisers (i.e. SolarEdge) or micro-inverters which will allow the system to cope with different levels of output across the panels. A Solaredge system (while more expensive) comes with decent enough monitoring software so you wouldn't need to pay for that as an extra.

Does that mean that they could produce almost double the Solar Century quote said they could? That would be my entire electricity consumption.

If the azimuth is the direction the roof is facing in then SE (135degrees) makes the output 2100. Half the roof faces NE, half faces SE. Which is still better than the quote I have.

Martyn1981

A few quibbles. They are using the post April export rate of 5.03p, but the pre April FiT rate. It's now 4.04p/kWh. Not a massive difference, but a little scary that they've got a key detail wrong.

The generation does seem low, as ET says go to PVGIS and test it yourself. My systems are similar(ish) at 110d and 290d orientation, but I get around 780kWh/kWp despite having a large chimney to the centre south of all my PV.

You obviously can't just compare one location to another but at 3.24kWp, I'd have thought something closer to 2,400kWh pa would have been expected.

I can't visually compare that GoodWe3000 to any of the current range on their site, so I couldn't check if it was a single or dual MPPT inverter. This is essential information, you need a dual MPPT inverter as it needs to treat the two rooves as separate arrays, otherwise the poorer performing array will pull down the better.

Ideally for £5k you'd want to get about 4kWp of PV, and as ET points out 'normal' panels are getting more efficient (more Wp per panel), so whilst 270Wp is ok, it's not great given that you have limited space. A good thing about more powerful panels is that they pull down the average cost of the system, when divided by output, as they don't need any extra scaffolding, labour, rails etc etc.

Martyn1981

tumptyteapot wrote: »

Does that mean that they could produce almost double the Solar Century quote said they could? That would be my entire electricity consumption.

If the azimuth is the direction the roof is facing in then SE (135degrees) makes the output 2100. Half the roof faces NE, half faces SE. Which is still better than the quote I have.

They won't double the figure as you've left it at south facing (zero azimuth). The 130d SE needs to be entered as -50 azimuth, and the 310d NW needs to be entered as 130 (or +130) azimuth.

Also change the roof pitch to 20d, which might help a bit with E/W results, assuming the roof pitch is 20d.

tunnel

I've pinned North London as your location going on the fact that the company is based in London
For the SE roof I get 1690kWh and the NW roof 975kWh giving a total of 2665kWh. Obviously with not knowing your location this is just an estimate, there's also the consideration of the 2 x chimneys on the SE side of your property(from google earth pic) of which the shading is more manageable with solaredge or micros.
May be clutching at straws here but do you know the measurements of your rooves? It may be possible to get more on the SE if the panels were in landscape rather than portrait hence making better use of the better roof.

Exiled_Tyke

With today's poor FIT rates should a NW or NE roof really be considered viable?

Martyn1981

Exiled_Tyke wrote: »

With today's poor FIT rates should a NW or NE roof really be considered viable?

If it's part of an install that's going to happen anyway. The cost of adding PV to the NW roof will be proportionately low making up for the lower generation.

Just an example, but imagine a 4kWp south facing system for £4k, or an 8kWp system utilising the north roof too for £6k (50% more).

The north roof will be about 55% efficient at 35d pitch, or about 65% efficient at 20d pitch. For very steep rooves it isn't worth doing.