New build eco-house solar pv and battery sizing

[biff]

If you are not going off grid,
                                Then it is pointless getting a large array and massive storage battery bank. All you would need is a 4kw array, even less and enough storage to tide you over an outage of 48 hours.
  Getting a large array with no storage is just generating free lecky for the company.
  Yet if there is potential for an off grid installation situation, then it should be carefully calculated to see what figures will be required to run the dwelling comfortably. Off grid installations do not have to be a hardship Spend the money correctly at the beginning, invest in good technology, avoid complicated stuff and run with as high a voltage as possible in DC . Our Battery bank would be the single biggest expense, 60 forklift cells but they can take strings of pv at 140vdc+, and do not need any fancy Mmtp controllers. The juice just gallops across the lawn and into the 2 ton of lead acid.
  Our inverter is only 2kw but plenty to run all our appliances, including the washing machine.
  PV is so inexpensive and trouble free these days that it would be a sin not go go offgrid and run bill free for the 8 months alone, , Our wind turbine is my first love and I admire it as it battles away through the winter and delivers the goods of as AG says, " Cuts the mustard".
  I have less love for the Irish ESB than Billi has and would not piddle on them to put their fire out. They have prevented Ireland from taking advantage of our potential to be leading lights in the renewable energy stakes. We never took that into consideration when we handed it over to the Troika.
   If not going off grid, you will only needs a few days at the most for storage and with proper management of freezers and circulations pumps, fossil fuel driven GSHP for the duration of the outage, then it is not a large installation at all. On grid or off grid it don,t really matter but you should always have a backup up plan in case of prolonged outage and investing in a small economic generator that can be stored properly is a must.
                           Biff

[Pile-o-stone]

Solar PV is so cheap now that I would "fit as much solar as you can" as you will never have enough in winter, you will wish you had more in Spring / Autumn and you can always sell excess back to the grid in summer. This is especially so if your friend is going for a Powerwall as this will help soak up the excess generation.

I was about to post exactly this, but nowty saved me the effort.

In the UK you're looking to generate enough on dull summer and short winter days to cover as much of your usage as possible. The more panels, the more coverage. One of the costs in installing solar panels is renting the scaffold. If you pal is building a house, then he would have this cost anyway, plus if he fits roof integrated panels he'll not only benefit from enhanced aesthetics, he can save on roof tiles.

[biff]

Definitely  not intergrated PC panels.
          Pv performs better with 100mm space between pv and roof.
                  Biff

[Sprinter]

If he could i would actually go East and West facing rather than South, To me South only ever made sense if you are trying to maximise FITS payments or just happen to use peak energy at midday.

I am fully west facing and on a perfect day we peak at late afternoon around 17:00 just when we are cooking tea, things are a bit sparse in the mornings but we are getting enough to cover most of the houses background needs.

We have batteries and when they are working, its nice to have them topped off at the end of the day ready for the evening, however i also agree with more is better when it comes with solar, with our peak in the late afternoon i am considering putting some east facing ones up to catch the morning sun and top us up a bit faster, this would also give us a higher incoming baseling for longer, then of course i will add other things like a sunamp at some point in the future to make more use of it.

As for battery storage, whatever you go for its never enough, i should be increasing to 8 kWh next week (if the supplier ever gets their act together), we started with 4 and was impressed, then we increased to 6 and was more impressed, now we are going to 8 and i am already aware that for a lot of the year we will never fill them up unless we mains charge, hence i am now also considering east facing panels to help collect useful amounts for longer in the year.

but when it comes to "Need" if Need can be considered "N" then the equation for the correct amount of battery or solar will always be "N+1", which to be honest is the same formula i use to work out how many fishing rods, motorbikes, pushbikes Etc that i need, a very simple equasion and rarely wrong (unless the wife manages to count my fishing rods).

[jtp10000]

Definitely  not intergrated PC panels.
          Pv performs better with 100mm space between pv and roof.
                  Biff

Is this why my 4kw panels have never, according to the Enlighten gizmo, produced more than 3.5kw of power?

[biff]

I cannot speak for your installation  jtp10,000,
                   No 1 is the fact that integrating with the roof like they do in France blocks the cool air from reaching the rear of the panels and if there is any kind of hot weather the Panels output drops some 10 to 15% of its potential. The pv light cells need to be able to dump the heat freely.
      No 2 is more of a structural maintenance problem. Flashing integrated  panels is both a headache and a nightmare. It is simply the worst way to do it. Its is foolishly more about looks than efficiency.
     Biff

[Scruff]

PV is very useful.
Batteries without utility power are very useful.
Any clean power you make is great.
Battery lifecycle and supporting system costs do not make financial sense at a domestic civilian level I think it's just fashionable.
I have many many batteries, different flavours different breeds; doing all sorts of wonderful things. None of them offer me cheaper kWh cost than utility power.
Keeping the lights on in a power cut  

Batteries aren't green they're a catalyst to green. If used for soft gridding they and their supporting hardware are generating operational losses that could otherwise be offsetting a gas-fired utility turbine.

[dickster]

If I had my time again and given the right circumstance, my new build would have a single plane roof completely covered in solar panels. In fact I'd be looking at ways to use the panels as large roofing tiles and forming the roof itself. So that is solar maximized and then battery storage can come along any time incrementally in the future.

[biff]

  To Quote Scruff,    "Batteries aren,t green",
                That is true,  However in respect of some specific purpose not just life critical but other dedicated select purposes, then batteries are invaluable. They are the greenest answer when the mains are down, If these grid batteries can keep the freezers going and the circulation pups going and the ground sourced heat pumps going, then, they are indeed a valuable green asset in time of need. There are quite a few pounds worth of food locked away in these freezers during the summer when the power is really needed to keep them cool and fresh.
                                           Biff