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