Grid tie will be the best and cheapest.... and 5kw should do all you need for that application.
If you want off grid real living, you need 10kw solar, and that will probably cover you in all weather but the meanest... maybe do poorly for 20 days of the year.
For that and that budget, then 10 kw panels is just over 6000, 6-8kw inverter in the $500 mark if you build your own PJ style, and the charge controller will be about 50 dollars for 100 amps @ 48v If your panels are 60 cell 6x6 poly or monocells, then mppt is a waste of time. ( good thing.. not bad)
So save the money from the expensive charge controller and inverter and put it toward batteries. If you can get 35kwh for the remainder of money, you will have a full house system, that you may never need to turn over to the grid except for very dark days.
If you want commercial gear, then you will be better to go all out grid tie, as the alternative is a pretty minimalist system, and will require house rewiring as you said. If you go all out, then a change over switch will suffice, and that rewire money goes towards more battery or solar until you run out of budget..... more solar more solar is the mantra.
I am currently making a 35kwh system for a remote island here, and it will come in at the $10000 AUD mark. It will have 35kwh battery ( trojan) 8kw pure sine inverter, 40x 250 watt panels, 100 amp min solar controller.... it will run a 2500 watt hot water system ( about 4kwh/day) and reverse split system air conditioning.... and desalination unit...... very similar to mine here.
Very rarely go below 75% charge in the battery system because of the solar array being so big..... every day.... so battery life is extended dramatically >10 years on the trojan T105-RE
Note: get more panels, but do not point them all south trying to get the best with or without mppt, you don't want that, you want steady all day solar from all directions when overcast... plenty to the east for morning ( you will be charged up by lunch time probably to 85% or more ) some to the west for late evening top up, and the rest south for main bulk charge... thats the plan I found works best.
If the sun is out, you won't need much array to push the batteries hard, but even thats only for a few hours before it backs off... ie 60-70 amps is all you want for 3 hours to cover last night... the rest of the time will be spent in late absorb and only in the 15-40 amps.... no need to try to pay for mppt at all.... you don't want or need it, it will be a liability. 10kw will be quite capable of 80-100 amps.... more than we want at any one time... we want less for longer.... don't try to optimise in this case... spread you bets around the sky.
ie 3kw is enough on a sunny day, so plan for the worst days only, and the good ones will be just a joke. If you design for the good days, it is a waste of effort i think.... and solar guru's have not caught on to the fact that solar is cheap now, and their advise is out of date in a lot of cases, trying to get the last drop out of the array, when a bigger array is much cheaper than all the fixes and compromises they come up with... nut then they would be out of a job I suppose.....
Thats how I did it anyway, and it works flawlessly, and the boss does not really even know she is off grid. Does not do housework or anything else with the sun in mind.... just does as she pleases.
................oztules
.................oztules