Solar install, East / West split or all East

I'm considering getting pv solar installed on my property. I have a pitched roof with one side mostly facing east and the other west; however the ridgeline runs about 10 degrees to 190 degrees (so the west facing roof is 10 degrees to north).

My challenge is two suppliers have said to go for 2kw on the east roof and 2kw on the west; however one provider has said to put 4kw on the east roof as the west roof is 10 degrees to north.

Can anyone offer any advice? Obviously I don't want to commit to the project and choose the wrong option!

Cheers for any tips in advance.... Adrian

Replies

  • dm827430dm827430 Forumite
    57 Posts
    without knowing where you live, east/west is hardly the best orientation for solar (whether thats pv or water heating). obv every installation is different, but, have you considered heatpumps, air or ground as an alternative?
    the simple answer is its far too complicated for a forum to give you the best answer for your individual circumstances .
    personally i'd seek advice from a local company that specialises in renewables, rather than generic "solar" installers.

    Sorry if my view has muddied the waters!
  • Martyn1981Martyn1981 Forumite
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    lazyade wrote: »
    I'm considering getting pv solar installed on my property. I have a pitched roof with one side mostly facing east and the other west; however the ridgeline runs about 10 degrees to 190 degrees (so the west facing roof is 10 degrees to north).

    My challenge is two suppliers have said to go for 2kw on the east roof and 2kw on the west; however one provider has said to put 4kw on the east roof as the west roof is 10 degrees to north.

    Can anyone offer any advice? Obviously I don't want to commit to the project and choose the wrong option!

    Cheers for any tips in advance.... Adrian

    Hiya Adrian, I can chuck loads of info at you, but whether or not it's worth doing will depend on your location, as the further north you are, the lower your generation will be, and you're already facing approximately 20% less than a south facing install.

    Happy to help you work out some guesstimates of annual generation, but you'll also need price quotes to decide if it's worth doing.

    There's some starter info here, post#1 sections 1 and 2:

    http://forums.moneysavingexpert.com/showthread.php?t=3872445

    Now, onto roofs. I'm in a similar boat, as my E/W split is E+20deg and W+20deg, slightly more than you. Very, very roughly, if you split evenly (say 2kWp E and 2kWp W) then the E+ and W- generation would balance out at about equal to all East, or all West. (The pluses and minuses mean better or worse than exactly East or West).

    Purely for gross generation, then your E+ roof will produce more units pa, than a mix of E+ / W-. Won't be a massive difference, but worth considering. [Just checked for my location, and 4kWp at E+10deg = 3,200kWh's pa, & W+10deg = 2,900kWh's pa, so a 50/50 split would give 3,050kWh's pa.]

    However, for leccy savings, you might do better to have a mix as this will lengthen your generation day, with a lower flatter curve through the day - hope that makes sense, sounds a bit sloppy (sorry).

    Also key to leccy savings will be your daytime use, if you aren't around much till teatime, then some West generation may be beneficial, or alternatively, if you use loads in the morning, then higher East gen will be beneficial.

    Next .... you could of course mix and match, by putting say 6 panels on the West and 10 panels on the East, but you'll need to discuss with installers, to ensure you get a suitable inverter, that can cope with the lower West voltages. [Note: for a split system you'll need an inverter with 2 MPPT's (don't worry about what they are) but you will need these. Not a problem as loads of 2MPPT quality inverters are available.]

    Moving on .... you could also go over 4kWp total, as it sounds like you have a largish roof. So perhaps 3kWp East and 2kWp West. This will however mean a slightly lower FIT rate of 13.9p instead of the upto 4kWp rate of 15.44p (these change to 13.5p & 14.9p respectively from 1/7/13).

    This very recent thread chats about the pro's and con's of going bigger on a split system (look for me and Roger chatting):

    http://forums.moneysavingexpert.com/showthread.php?t=4567789

    Sorry to chuck so much at you, bet you wish you'd never asked now!

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • EctophileEctophile Forumite
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    Personally, in that situation I'd go for an east/west split.

    If your main aim is "farming" feed-in tariffs, then just going for the east roof would be better, as it gets more sun. However, you will only be generating lots of electricity in the morning, which isn't when most people need it. If you add a west roof, you will be generating into the early evening, especially in summer, when the sun sets in the north-west.

    My (only) roof faces south-east. I lose the direct sunshine mid-afternoon. So by the evening, when I most want free electricity, I'm getting very little.
    If it sticks, force it.
    If it breaks, well it wasn't working right anyway.
  • rogerblackrogerblack Forumite
    9.4K Posts
    Ectophile wrote: »
    Personally, in that situation I'd go for an east/west split.

    Assuming both roofs are totally unshaded.
    Even quite low obstructions in the sky can greatly reduce output. Far more than south facing roofs.
  • edited 4 May 2013 at 9:31PM
    Kernel_SandersKernel_Sanders Forumite
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    edited 4 May 2013 at 9:31PM
    dm827430 wrote: »
    without knowing where you live, east/west is hardly the best orientation for solar (whether thats pv or water heating). obv every installation is different, but, have you considered heatpumps, air or ground as an alternative?
    the simple answer is its far too complicated for a forum to give you the best answer for your individual circumstances .
    personally i'd seek advice from a local company that specialises in renewables, rather than generic "solar" installers.
    This is amongst the worst advice I've ever seen on MSE.
    Firstly, even a west or east facing PV system on FiT will be a far better investment over its lifetime than any heatpump.
    Secondly, I've found over my life that some of the least appropriate advice comes from those with a financial interest in you taking it.
    Thirdly, the regulars on this board are more than capable of recommending a suitable setup, providing they have all the relevant information such as possible shading and pitch.
  • dm827430dm827430 Forumite
    57 Posts
    This is amongst the worst advice I've ever seen on MSE.
    Firstly, even a west or east facing PV system on FiT will be a far better investment over its lifetime than any heatpump.
    Secondly, I've found over my life that some of the least appropriate advice comes from those with a financial interest in you taking it.
    Thirdly, the regulars on this board are more than capable of recommending a suitable setup, providing they have all the relevant information such as possible shading and pitch.
    worst advice ever - really?
    get advice from a local specialist is somehow bad advice.
    heatpumps are always worse than pv? surely the point is every location is individual. Personally we get limited sunlight outwith mid summer, but are able to take advantage of old mine workings (and a LA grant).
    Nonsense posts assuming this and that hardly help the OP.
    If he'd posted a heap of data im sure someone could have come up with a perfect solution , without seeing the site, you cant possibly condemn anyone elses view. Maybe a NPP would be his ideal energy supply?
  • danesoldanesol Forumite
    46 Posts
    lazyade wrote: »
    I'm considering getting pv solar installed on my property. I have a pitched roof with one side mostly facing east and the other west; however the ridgeline runs about 10 degrees to 190 degrees (so the west facing roof is 10 degrees to north).

    My challenge is two suppliers have said to go for 2kw on the east roof and 2kw on the west; however one provider has said to put 4kw on the east roof as the west roof is 10 degrees to north.

    Can anyone offer any advice? Obviously I don't want to commit to the project and choose the wrong option!

    Cheers for any tips in advance.... Adrian


    System design is one thing but there is still the question of localised weather to consider :)

    Example:- I have exactly the same sized system as someone who lives to the West of me - same panels ( Sanyo Hits), different inverter.

    I'm facing more or less due South using SMA, they are facing South West using Power1

    Guess who seems to do better overall ??

    System design software etc will tell you that South is best but if you have clouds and bad weather mid morning - the SW system will do far better but when the sun is out from 9am onwards my South base system will crucify the SW system !!

    At the moment there is 5kwh difference between us :D


    Unless you get a decent low price system installed within 6weeks - forget as the returns wont justify the investment. They may claim you save loads on your electric bills but if you aint there to use it - you wont have any savings there either unless that is you look at home automation and/or Solar Immersion ( proportonal switching ) :)
    2.88kWp, Panels: 12 Sanyo 240HiTs, Inverter: SMA SB 3000hf
    Solarimmersion proportional device fitted
    Location: Cheshire, Roof: South, 30 degree pitch
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