Roof orientation and panels

ispookie666

Recently had a solar survey done for the roof and the installer has come up with 7x 340W panesl in a 3 + 4 split on the roof towards the rear of the house. 
The front of the house/roof is facing NE and the only south facing roof is the rear (the roof which appears sunlit!). The roof in the front part of the house gets sun during the morning, is there any point in putting a few panels (around 3)?  The whole idea being able to generate enough to match the consumption. We used to have 3.5KWp panels in our old home with enphase 215 micro inverters and hoping to maximise what we can have in our current house.   
  

matelodave

Use the PVGIS calculator to try and work out what output you could expect to achieve based on your ost of three panels that only get sun for a couple of hours a day is worth it .(probably less in the winter  or when the sun isn't in its optimum position)

QrizB

I don't suppose you can turn your house clockwise through 90 degrees, can you?

Not knowing where you are, I've looked in PVGIS at my own location (central southern England). Here 1kWp of panels on your front roof would produce about 640kWh per year, compared to 995kWh if facing south. That's a 36% reduction and they're essentiually useless from November to February.

If the installer can fit them at a low enough additional price they might be worth it but anything over 60-65p per watt is unlikely to be worth it IMHO. (The last PV system I had installed, the installer had a base price for the system and let me add/delete 360W panels for £200 each.)

ispookie666

matelodave said:

Use the PVGIS calculator to try and work out what output you could expect to achieve based on your ost of three panels that only get sun for a couple of hours a day is worth it .(probably less in the winter  or when the sun isn't in its optimum position)

Had a look and thank for the suggestion @matelodave 
If I add 4 x 340 panels on the front - would loose around 300 KWh production over the year bringing the value to 880KWh and if I add the other panels, the whole expected generation comes to 3100 KWh from an installed capacity of 3.7KWp
@QrizB thanks for the suggestions - the installer which quoted me was not very keen on micro inverter. 
Let me see if the installer will bite, as he had suggested a standalone inverter and tracking. I only have had experience with enphase microinverter (M215) in my old house.  

QrizB

I don't think you'll need micro inverters but if you choose them, they won't do any harm and you can ignore my next sentence.

The panels on the front of your roof will need to be a separate string to the ones on the rear. Either two separate inverters or one dual-MPPT inverter.

matelodave

As above, you need to ensure that the panels that get shaded are on a separate string otherwise the shading could bring the whole output down - thats why micro inverters can be a benefit if there's any shading on any of the panels during the day. Take into account trees and even telegraph poles especially during the spring, autumn and winter when the sun is pretty low in the sky and ahadows can be a lot longer.

ispookie666

Decided to litter the roof with panels and having everything in one go.  Hopefully install in the 3rd week of Jan.  
20 x 330W panels split as 12-4-4 on Roof orientation (degrees from south) - 115, 25, 25 
Enphase micro inverters 
Givenergy AC coupled inverter along with 2x 8.4KW Givenergy battery (not sure when this will be installed) 
iBoost 
Managed to burn a hole in my pocket 

Magnitio

You hadn't mentioned the installation of a battery before. I would have said that if installing a battery, then you would want to maximise the total daily output from the panels rather than worrying about spreading the output through the day by using less optimal roof-space. Interested in views on this.

ispookie666

@Magnitio It started out as just the panels, then the usual mission creep! 
I'm hoping I'd be able to get the battery backup to power critical loads during a power cut. 

Magnitio

@ispookie666 The installer I am using is adding a couple of sockets that will provide power  from the Givenergy battery/inverter in the event of an outage. This was the simplest/cheapest option and allows us to plug in fridge/freezer and any other essentials when needed.

ispookie666

Finally had the system installed 
6.6KWp, it's cost me an arm, hopefully the panels will be able to provide enough leccy.  
20 Jinko 330W 
Enphase IQ7+ micro inverter 
Envoy S 

The emergency backup from the Givenergy will supply the lights and garage sockets.