Have some Solar Panel quotes - was looking for advice

flyinggoose

Hello,

So i have been in touch with about fourteen companies in and around my area (north west) looking for quotes, I have three roofs the panels can go on, two roofs face southwards (south east and south west) while the other faces north west.

I have been asking for quotes for panels on two roofs and also three roofs (solar panels only, no battery storage for now), the following are the best quotes i've received (all the quotes i received have been desktop quotes):

Panels over two roofs

4.29kWp System

£1.36 / kWp

Panels: Trina Vertex S all black390w x 11

Sofar 3.6 KTLM Dual Tracker x 1

£5875

Panels over three roofs

6.63kWp System

£1.35 / kWp

Panels: Trina Vertex S all black390w x 17

SolarEdge HD Wave 6000 wifi &Export Manager x 1

SolarEdge Power Optimisers x 17

£8983

The above two quotes do not include bird mesh (which i definitely will need) as this company doesn't provide that service, so that would be an additional cost on top of the quotes.

The third quote i have (from a completely different company) includes bird mesh and is as follows:

Panels over three roofs

5kWp System

£1.30 / kWp

Modules: Longi 360w Black Solar Panel x 14

Inverter: SolarEdge x 1

Power Optimisers x 14

Bird Deterrent x 1

£6495

The same company that's given the third quote also gave a quote for two roofs but that was a 3.2kWp system for £4975 with a SoFar inverter so i just discarded that (worked out £1.55 / kWp).

The north roof obviously won't get as much sun however i am trying to get as big of a system up there as possible for a good price and the third quote seemed like a sweet spot in terms of system size and price, i do intend to get battery storage in a few years time when the tech has improved and prices have hopefully come down further.

I just wanted to ask here what people thought of the above quotes before i went ahead with the installation and any other advice would also be appreciated, the aim is to be as self sufficient as possible from the electrical grid (I'm aware this isn't easy and depends on usage) in a few years time once a large battery is added so going for as large of a system as possible would make sense but thought i'd ask nonetheless as i might be missing something.

Spies

Where are you roughly based and how many panels will go on the North roof? 

flyinggoose

I'm in Lancashire, it'll be about five panels on the North roof.

Spies

They will very little towards you generation in the 6 winter months, I dont think the extra expense for those would be worthwhile.

thevilla

I have a 50:50 split North South on a 20 degree roof pitch. Over a year, the North panels produce approximately 70% of those facing south.  The pitch is important as, at 20 degrees, the sun is now rising high enough to strike them directly.  A bigger angle would obviously delay that to later in the year.

Martyn1981

I wouldn't discount the NW panels, but I think they need to come with some 'IFs'.

IF you have some shading issues on the other two roofs, and would benefit from a Solaredge system, then adding some extra panels to the NW at the same time makes sense.

IF there are no additional scaffolding costs, or minimal, then that also makes sense.

IF you are aware that generation from the NW will be poorer per annum, and limited in the winter, but perhaps will enjoy some late generation in the summer months, then also ok.

Just for clarity, I have two Solaredge systems, and one is WNW. This may sound petty, but WNW is not great, and it rapidly gets worse as you head towards NW*. However, SE + SW is an excellent combination, possibly (in my opinion) better than just a single south facing roof. So NW as a top up for a great system, might be a reasonable addition if you can spare the money.

*So really worth checking PVGISand comparing annual generation. For my house PVGIS suggests 752kWh/kWp for 30d pitch roof WNW, and 647kWh/kWp for NW. Hmmm I think I'd add the NW panels if it was me, assuming Solaredge is worth it.

Exiled_Tyke

I have to agree with Martyn.

 If the other two roofs don't have serious shading issues then you can spare the additional cost of SolarEdge by going with a two string system and just stick to the two roofs.  So I think the additional costs of going onto the NW may be significant and not worth it or indeed if you crunch the numbers may make sense for the additional generation.  

Could you get quote 3 to upgrade the panels? Then I'd be more tempted.

2nd_time_buyer

Am I right is saying that with PVGIS it does not take into account the horizon by default? The further away from South the roof I guess this is more of a factor. I suspect it will results in a big difference between a house in the open compared to a house in a built up area in the low-sun months.

In the Solaredge design software you can add the effect of surround houses etc. And it certainly seems to make a significant difference. 

Verdigris

It says "use terrain shadows", as default, which I take to mean hills but not built structures. There is a facility to load in custom files but I've no idea how you create/find them.

Martyn1981

2nd_time_buyer said:

Am I right is saying that with PVGIS it does not take into account the horizon by default? The further away from South the roof I guess this is more of a factor. I suspect it will results in a big difference between a house in the open compared to a house in a built up area in the low-sun months.

In the Solaredge design software you can add the effect of surround houses etc. And it certainly seems to make a significant difference. 

Good question, I've no idea. But what I can say is that I live in a built up area, well suburbs, so no high rise properties, but half way down a hill, and my generation on average, is slightly better than the PVGIS guesstimate for unshaded roofs. So I think the slightly pessimistic numbers from PVGIS (14% default losses) match my shading losses, but also need to take into account that Solaredge is doing its best to minimise the shading impacts.

Verdigris

I assume PVGIS takes average cloud cover into account. It's only showing 6600 kWh from 8 kWp for my new gaff but the rainfall is more or less 100mm/month (even June is 88mm), all year, so presumably often cloudy.